Animals II Summary Notes PDF

Animals II Summary Notes Classification & Nomenclature Classification – The arrangement of kinds of animals in a hierarchy of smaller and larger groups Nomenclature – The procedure of assigning names to the kinds and groups of animals Phylogeny – The evolutionary history of a group Characteristics of the Animal Kingdom Animals vary in complexity & are classified based on anatomy, morphology, genetic makeup & evolutionary history Animals are heterotrophs - they must consume living or dead organisms since they cannot synthesize their own food (derive energy from food) o A black bear is an omnivore - eating both plants & animals o A heartworm is a parasite that derives energy from its hosts - spends its larval stage in mosquitoes & its adult stage infesting the heart of dogs & other mammals Animals can be carnivores, herbivores, omnivores, or parasites Complex Tissue Structure Animal cells don't have cell walls o Their cells may be embedded in an extracellular matrix & have unique structures for intercellular communication Animals have nerve & muscle tissues o Which provide coordination & movement o These are not present in plants & fungi Complex animal bodies demand connective tissues that provide support & structure Animals are also characterized by epithelial tissues, like the epidermis, which function in secretion & protection The animal kingdom is divided into o Parazoa (sponges), which do not contain true specialized tissues o Eumetazoa (all other animals), which do contain true specialized tissues Animal Characterization Based on Body Symmetry Animals with radial symmetry have no right or left sides, only a top or bottom o Usually marine organisms like jellyfish and corals Most animals are bilaterally symmetrical with a line of symmetry dividing their body into left & right sides along with a "head" & "tail" in addition to a top & bottom The 6 Kingdoms 1. Animalia 2. Plantae 3. Fungi 4. Archaea 5. Monera (bacteria) 6. Protista (single cell organisms) Classification Animals are classified according to common characteristics This results in a classification hierarchy This hierarchy works from most inclusive to most exclusive Species A group of individuals that interbreed under natural conditions to produce viable young which are reproductively isolated from other groups When species are discovered they are given scientific names using the binomial system. Rules of nomenclature Zoological & botanical names are distinct No two genera or species can have the same name Scientific names in Latin Genus is a single word & the first letter is a capital The specific name a single word & the first letter is a small letter When writing the scientific name it is underlined or in italics The author of a scientific name is the first person who published it Example: o Eland – Taurotragus oryx Pallas or Taurotragus oryx Phylum Chordata 1. Subphylum Urochordata Class Ascidiacea (Redbait) 2. Subphylum Cephalochordata Class Leptocardii (Lancelets) 3. Subphylum Vertebrata Class Cyclostomata (Lampreys & hagfish) Class Osteichthyes (Bony fish) Class Chondrichthyes (Cartilaginous fish) Class Amphibia (Amphibians) Class Reptilia (Reptiles) Class Aves (Birds) Class Mammalia (Mammals) 5 characteristics of Chordates 1. Single, hollow nerve cord beneath dorsal surface; in vertebrates, it differentiates into brain & spinal cord 2. Notocord: flexible rod on the dorsal side of gut, present at one stage in all chordates; displaced in vertebrates by vertebral column that forms around the nerve cord 3. Pharyngeal slits (pouches) connect pharynx (between mouth & esophagus) with outside gills in sharks, fish; present in terrestrial animal embryos but disappear later, except Eustachian tube (connecting throat & middle ear) 4. Post-anal tail extends beyond anus; present at least in embryo; regresses into tail bone in humans 5. Endostyle or Thyroid Gland Dorsal Hollow Nerve Cord The dorsal hollow nerve cord derives from ectoderm that rolls into a hollow tube during development In chordates, it is located dorsally (at the top of the animal) to the notochord In contrast to the chordates, other animal phyla are characterized by solid nerve cords that are located either ventrally or laterally The nerve cord found in most chordate embryos develops into the brain & spinal cord, which comprise the central nervous system Notochord The chordates are named for the notochord A flexible, rod-shaped structure that is found in the embryonic stage of all chordates & also in the adult stage of some chordate species It is located between the digestive tube & the nerve cord, providing skeletal support through the length of the body In some chordates, the notochord acts as the primary axial support of the body throughout the animal's lifetime In vertebrates, the notochord is present during embryonic development o Replaced by the vertebral column (spine) in most adult vertebrates Pharyngeal Slits Pharyngeal slits are openings in the pharynx (the region just posterior to the mouth) that extend to the outside environment In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth In vertebrate fishes, the pharyngeal slits develop into gill arches, the bony or cartilaginous gill supports In most terrestrial animals (including mammals & birds) pharyngeal slits are present only during embryonic development o In these animals, the pharyngeal slits develop into the jaw & inner ear bones Post-anal Tail The post-anal tail is a posterior elongation of the body, extending beyond the anus The tail contains skeletal elements & muscles, which provide a source of locomotion in aquatic species The notochord & nerve cord extend to the tail Found at some time during a chordate’s development In some terrestrial vertebrates, the tail also helps with balance, courting & signalling when danger is near In humans & other apes, the post-anal tail is present during embryonic development, but is vestigial as an adult Endostyle or Thyroid Gland Until recently the endostyle was not recognised as a chordate character Its derivative, the thyroid gland is found in all chordates, but in no other animals The endostyle is located in the pharyngeal floor & secretes mucus that traps small food particles brought into the pharyngeal cavity An endostyle is found in protochordates & lamprey larvae In primitive chordates, endostyle & perforated pharynx work together to create an efficient filter feeding apparatus The endostyle in the pharyngeal floor secretes mucus that traps food particles o Found in protochordates & lamprey larvae o Secretes iodinated proteins Homologous to iodinated-hormone-secreting thyroid gland in adult lampreys & other vertebrates Adult Lamprey & Larvae o The thyroid is a butterfly-shaped gland that sits low on the front of the neck o Your thyroid lies below your Adam’s apple, along the front of the windpipe o The thyroid has 2 side lobes, connected by a bridge (isthmus) in the middle o When the thyroid is its normal size, you can’t feel it Classification The arrangement of kinds of animals in a hierarchy of smaller and larger groups 1. Sub-phylum Urochordata EG sea squirts & red bait Only larva has dorsal notochord & dorsal nerve chord = TUNICATA = INVERTEBRATE 2. Sub-phylum Cephalochordates EG lancelets Adult has dorsal notochord & dorsal nerve chord Invertebrates 3. Sub-phylum Vertebrata EG fish Adult has dorsal vertebral column, dorsal nerve chord & well developed brain The body covering is a stratified epithelium of epidermis & dermis with mucous glands in most species The internal & jointed skeleton is of cartilage in lower vertebrates & of bone in higher groups On the skeleton are muscles important in locomotion The digestive tract is complete o The mouth typically contains teeth & two large digestive glands o The liver & pancreas are typically present The circulatory system includes a well developed muscular heart which circulates blood through a closed system of arteries & veins o The blood contains white & red corpuscles, the latter contains the respiratory pigment haemoglobin Respiration is by gills in the lower forms & by lungs in the higher forms The excretory organs are paired kidneys The brain is regionally differentiated as to structure & function Endocrine glands provide hormones which regulate bodily processes, growth & reproduction The sexes are typically separate 1. Class Cyclostomata – Lampreys & Hagfishes (EG slime eels) 2. Class Chondrichthyes – cartilaginous fishes o Sub-class Holocephali – elephant sharks o Sub-class Elasmobranchii – sharks and rays 3. Class Oesteichthyes – bony fishes o Sub-class Actinopterygii - ray-finned fishes o Sub-class Sarcopterygii - lobe-finned fishes 4. Class Amphibia – amphibians 5. Class Reptilia – reptiles 6. Class Aves – birds 7. Class Mammalia – mammals Mind Map Skin (covering) Skeleton Circulatory system Respiratory system Digestive system Excretory system Nervous system Endocrine system Reproduction Locomotion Characteristics Skin (covering) - The body covering is a stratified epithelium of epidermis & dermis with mucous glands in most species Skeleton - Internal & jointed skeleton is of cartilage in lower vertebrates & of bone in higher groups, on the skeleton are muscles (NB in locomotion) Circulatory system - Well developed muscular heart which circulates blood through a closed system of arteries & veins, the blood contains white & red corpuscles (contains the respiratory pigment haemoglobin) Respiratory system - By gills in the lower forms & by lungs in the higher forms Excretory system - paired kidneys Digestive system - Digestive tract is complete - the mouth typically contains teeth & two large digestive glands, the liver & pancreas are typically present Nervous system - Regionally differentiated as to structure & function Endocrine system - Provide hormones which regulate bodily processes, growth & reproduction Reproduction - Sexes typically separate Locomotion – A variety of appendages are utilized for locomotion Phylum chordata Includes some invertebrate groups & all the vertebrate animals It is distributed in all habitats o Marine, aquatic & terrestrial Includes all the large animals present on the earth today Consists of 2 different groups o Lower chordates ▪ Marine & small in size ▪ Lack a vertebrae in adult phase ▪ Including tunicates & lancelets o Higher chordates ▪ Free-living vertebrates ▪ Encompassing fish, amphibians, reptiles, birds & mammals Subphylum Urochordata (uro-kor-data) (Gr. oura, tail, L. chorda, cord, ata, characterized by) (Tunicata): tunicates. Notochord and nerve cord in free-swimming larva only; ascidian adults sessile, encased in tunic. About 1600 species. Urochordata – Tunicates Adult tunicates show little or no resemblance to other chordates They are all marine Few are free living as adults o Most are attached to rocks, shells, wharfs, pilings or ship hulls May be solitary, colonial, or have individual groups under a common covering Vary in size from microscopic to 30 cm in diameter 2000 species known – 100 pelagic Only the larval form has chordate characteristics Mostly hermaphroditic, some use sexual or asexual reproduction 3 phases of life 1. Larval Ascidian o Free swimming transparent larva o +/- 5mm in size with long tail o Tail contains a notochord, dorsal nerve chord, pairs of lateral segmented muscles o Anterior end contains remainder of organs & mucus or adhesive glands o Digestive tract is complete with mouth o Gill slits open into an atrium o Endostyle, o Intestine with anus o Circulatory system with blood vessels o Nervous system is relatively simple 2. Metamorphosis o Larva attaches by its adhesive glands to a rock after hours or days free swimming o Chordate features quickly disappear o Tail is partly absorbed & partly cast off o Notochord, nerve cord & muscles withdrawn into body & absorbed o Only the trunk ganglion of the nervous system remains o Body rotates so that the mouth is on the upper end o Brachial sac enlarges & develops many openings 3. Adult Ascidian o Cylindrical in shape attached by a base to a rock o Covered with tough elastic layer o Lined by a membranous mantle contain muscle fires & blood vessels o Two external openings ▪ Incurrent siphon at the top ▪ Ex-current siphon at the side o Water taken in bring oxygen & food o Out current removes wastes & sex cells o Atrial cavity has large brachial sac having many gill slits bordered by long cilia o Digestive system starts with incurrent ▪ Endostyle has a vertical groove lined with flagellated & mucous cells that moves food & water downward o This leads to oesophagus & to a stomach, then intestine & anus Class Ascideacea Class Thaliacea Class Larvacea Characteristics Skin (covering) - the body cylindrical & the covering is tough elastic layer of cellulose Skeleton – only larval stage has representation of Chordata Locomotion – only during larval stage in most species, adults are attached to substrate Digestive system – begins with incurrent siphon, where food is trapped then moved by flagellated & mucous cells towards the oesopagus & stomach, through the intestines an excreted through the anus by an outcurrent. Circulatory system – open circulatory system Respiratory system – brachial sac has many gills slits containing ciliated cells that beat to move water Excretory system - discharged from intestine via anus through excurrent siphon Nervous system – made up of a nerve ganglion and a plexus (network) of nerves Endocrine system – has endostyle Reproduction – hermaphroditic: single testis & ovary; gametes carried by ducts into atrial cavity & pass through excurrent siphon to outside in seawater where fertilization takes place Subphylum Cephalochordata Class Leptocardii Lancelets Order Branchiostomiformes (sefa-lo-kor-data) (Gr. kephal¯e, head, L. chorda, cord): lancelets (amphioxus). Notochord, nerve cord, and postanal tail persist throughout life; fishlike in form. 29 species. Closest living invertebrate relative of the vertebrates - vertebrate-like in having a dorsal, hollow nerve cord, notochord, segmental muscles, pharyngeal gill slits and a post-anal tail that develops from a tail bud Subphylum Cephalochordata Comprises of approx. 30 species of fish like animals Inhabit tropical & temperate seacoasts Body slender, long & laterally compressed No distinct head Body is single layer of soft epidermis with sensory processes Notochord is chief support of the body Buccal cirri are feeding structures found in the oral hood of primitive jawless organisms (like lancelets) Gonads are glands that produce hormones that are involved in reproduction and other functions of the body Atriopore is a hole in a lancelet through which water exits the body Myomeres function of bending their possessors' bodies from side to side to provide locomotor force Cephalochordates Characteristics Skin (covering) o Single layer of soft epidermis Locomotion o Only during larval stage in most species o Adults are attached to substrate Digestive system Simple digestive tract Mouth is circular & posterior to the oral hood Large compressed pharynx with diagonal gill slits followed by narrow straight intestine ending at the anus Circulatory system o The circulatory system does resemble that of primitive fish in its general layout o But is much simpler & does not include a heart o There are no blood cells & no haemoglobin (a protein found in the red blood cells that carries oxygen in your body and gives blood its red colour) Respiratory system o Lancelets have no respiratory system o Breathing solely through their skin, which consists of a simple epithelium Excretory system o Segmented "kidneys" (containing protonephridia instead of nephrons) Nervous system o Have a hollow nerve cord running along the back o The dorsal nerve cord is not protected by bone but by a simpler notochord made up of a cylinder of cells that are closely packed to form a toughened rod Endocrine system o Has endostyle (a longitudinal ciliated groove on the ventral wall of the pharynx which produces mucus to gather food particles) Reproduction o Cephalochordates have separate sexes o Eggs & sperm are released into the water flowing out of the atrium & fertilization is external Subphylum Vertebrata (verte-brata) (L. vertebratus, backboned) (Craniata): vertebrates. Bony or cartilaginous cranium (the part of the skull that encloses the brain) surrounding tripartite brain Well-developed head with paired sense organs Usually with vertebrae Heart present, with multiple chambers Muscularized digestive tract Paired kidneys. Class Cyclostomata Includes lampreys & hagfishes (slime eels) Lampries found in both salt & fresh waters Some lampreys are non parasitic Parasitic species attach by suction & buccal teeth Hagfishes only found in salt water Prefer muddy areas of sea floor, with lowlight & often high salinities Cyclostomes are found chiefly in temperate zones Can reach high latitudes & found in cool waters of both hemispheres Order Pefromyzonia Ex: Petromyzon (Sea-lamprey) ) Lampetra fluviatilis Order Myxinoidea Ex: Myxine glutinosa Hag-fish or slime eel). Eptatretus (Bdellostoma) Subphylum Vertebrata (Craniata) Superclass Myxinomorphi (superclass = the taxonomic rank that is subordinate to a phylum, or a subphylum, and superior to a class) Class Myxini – hagfishes o No jaws or paired fins o Mouth with four pairs of tentacles o Buccal funnel absent o 1 to 16 pairs of external gill openings o Vertebrae absent o Slime glands present o 70 species (marine) o They are the only vertebrate with a skull but no vertebrae o Barbel - any of several slender tactile spines or bristles that hang from the jaws (also on catfish & carp) o The branchial system is typically used for respiration &/or feeding o The olfactory glands produce mucous to lubricate the olfactory epithelium & dissolve odorant-containing gases Superclass Petromyzontomorphi Class Petromyzontida – lampreys o No jaws or paired fins o Mouth surrounded by keratinized teeth but no barbels, buccal funnel present ▪ Keratinized tissue - the band of tissue surrounding teeth at the point where they meet the gums ▪ Keratinized = cells that produce large amounts of a protein called keratin, making them strong & better at forming barriers o 7 pairs of external gill openings o Vertebrae present only as neural arches (the curved rear (dorsal) section of a vertebra, enclosing the canal through which the spinal cord passes) o 38 species (freshwater & anadromous) o Cloacal aperture serves as the digestive, reproductive, and urinary tract Lamprey Parasitic life cycle – ocean Lamprey Parasitic life cycle – landlocked Characteristics Skin (covering) o Body long, slender & cylindrical with no scales Skeleton o Skull cartilaginous o Notochord persistent o Vertebrae represented by small imperfect neural arches over notochord Locomotion o No paired fins, strong lateral movements of the body Digestive system o Mouth ventro-anterior o Suctorial in lampreys & biting in hagfishes - no true jaws o Straight & simple digestive system Circulatory system o Heart 2-chambered o Cold blooded (body temperature varies with that of the environment) Respiratory system o Gills in lateral saclike pouches off pharynx (throat) Excretory system o Mesonephric kidneys (also present in higher fish & amphibians, not mammals) o Nitrogenous wastes (waste product that contains nitrogen) mainly ammonia Endocrine system o Has endostyle Reproduction o Gonad (reproductive gland) single without duct o Fertilization external o Development direct (hagfishes) or with long larval stage (lampreys) Class Chondrichthyes & Osteichthyes Class Chondrichthyes Sharks, rays & chimaeras (ghost sharks) Have movable jaw Paired appendages o Not found in ancestral vertebrates o Means pectoral & pelvic fins present & used for locomotion The group is ancient (> 430 mya) - represented by many fossil remains Osteichthyes = Bony endoskeletons gave rise to a clade of vertebrates that contains 96% of living fishes & all living tetrapod’s (4 legged animals) Bone = strong, non-flexible, tough Cartilage = soft, flexible, light 4 NB characteristics 1. Cartilaginous skeleton 2. Teeth not fused to jaws & usually replaced o Continuously shed their teeth 3. No swim bladder o No swim bladder to adjust their buyoncy o Swim constantly to keep afloat, like a plane o Swim to let O2 pass through the gills o Bony fish have muscles to pump water & oxygen through their gills o What is a swim bladder? ▪ An oval sac in the abdomen just below the vertebral column ▪ Filled with air either from gulping or diffusion of gas from blood into bladder ▪ Air less dense than water, so fish have buoyancy 4. Intestine with spiral valve o Spiral valve = corkscrew shaped lower portion of the intestines o Coiled twisted to increase the surface area of the intestine which increases nutrient absorption o Intestines of shark much shorter than mammals o Can keep material in spiral valve for extended time periods for max nutrient absorption 5. Claspers present in males Lateral line system o Composed of a spatial array of water flow detectors (neuromasts receptor organs) o Narrow strip of sensory cells runs along the sides of the body & into the head o Plays critical roles in a variety of behavioural contexts (EG prey detection, predator avoidance, communication & navigation) o Picks up the vibrations in the water Sensitive olfactory receptors inside the nasal sac detect smells in extremely small concentrations & send nerve impulses to the brain Chondrichthyes Characteristics Skin (covering) o Skin tough o Covered with minute placoid scales (spiny, tooth like) & many mucous glands Skeleton o Skeleton cartilaginous o Notochord persistent o Many vertebrae o Vertebral column passes through the upper lobe making it the largest lobe o Pectoral & pelvic girdles (muscles) present o Median & paired fins present o Pelvic fins with claspers in males o Heterocercal tail (= caudal fin composed of 2 asymmetrical lobes) Circulatory system o Heart 2-chambered & contains only venous blood (deoxygenated blood that flows from tiny capillary blood vessels within the tissues into progressively larger veins to the heart) o Heart that pumps blood around the body in a single loop-from the heart to the gills, from the gills to the rest of the body, then back to the heart Respiratory system o Respiration by gills attached to opposing walls of 5-7 pairs of gill pouches o Each pouch with a separate slit-like opening o No swim bladder Digestive system o Mouth ventral (means at the front of the boday), with teeth o Both lower & upper jaws present o Intestine with spiral valve Excretory system o Excretion by mesonephric kidneys (Earlier form of kidney that spans the dorsal part of the animal) o Main nitrogenous waste is urea Nervous system o Brain of 2 cerebral hemispheres with well developed senses of smell, vision, electroreception & vibration reception Endocrine system o Multiple systems & complex endocrine system o Various endocrine glands have been found associated with different tasks & functions Reproduction o Sexes separate o Gonads (glands that produce hormones that are involved in reproduction & other functions of the body) typically paired o Reproductive ducts open into cloaca o Fertilization internal o Oviparous (egg laying – hatch after they have been laid) or ovoviviparous (egg laying but egg develops in parents body) Locomotion o Fins are stiff & non-flexible o Strong tail is used for most of forward motion o Rays use undulations of their pectoral fins for forward motion 2 – chambered heart Mesonephric kidneys Bulbus arteriosus - maintains a steady blood flow into the gill system through heart contraction The right atrium receives oxygen-poor blood from the body & pumps it to the right ventricle The right ventricle pumps the oxygen-poor blood to the lungs The left atrium receives oxygen-rich blood from the lungs & pumps it to the left ventricle The left ventricle pumps the oxygen-rich blood to the body Sinus venosus - specialized cardiac pacemaker tissue in many fish Class Oesteichthyes Bony fish Skeleton ossified o Ossification = formation of bone Single gill opening covered by operculum o Operculum = hard, plate-like bony flap that covers the gills of a bony fish Paired fins supported primarily by dermal rays Limb musculature within body o A tissue composed of fibers capable of contracting to effect bodily movement Swim bladder mainly a hydrostatic organ if present Atrium & ventricle not divided Teeth with enameloid covering o Enameloid is softer than enamel, containing a different mix of proteins Pyloric caeca (NB digestive/absorptive organ) - secrete enzymes & provide additional digestive areas to the intestine Osteichthyes Characteristics Skin (covering) o Skin with many mucous glands, typically with embedded bony dermal scales (cycloid, ctenoid) o Some scaleless ▪ EG catfish ▪ Scales protect fishes from pathogens & predators so without scales they become more susceptible to various pathogens ▪ In saltwater fish scales are very important for osmoregulation (the process of maintaining salt & water balance across membranes) Skeleton o Skeleton mainly of bone (cartilage in sturgeons & some others) o Many vertebrae, but relics of notochord often persist o Pectoral & pelvic girdles present o Both median & paired fins present (some exceptions), supported by fin rays of cartilage or bone o Tail usually homocercal (appearing outwardly symmetrical but with the backbone passing into the upper lobe) Circulatory system o Heart 2 - chambered containing only venous blood Respiratory system o Respiration by pairs of gills on bony gill arches in a common chamber at each side of pharynx, covered by a bony operculum o Usually with a swim bladder (buoyancy organ) Digestive system o Mouth usually terminal with teeth o Jaws well developed, articulated to skull Excretory system o Excretion by mesonephric kidneys o Main nitrogenous waste is urea Nervous system o Brain of 2 cerebral hemispheres with well-developed senses of smell, vision, electroreception & vibration reception Endocrine system o Multiple systems & complex endocrine system o Various endocrine glands have been found associated with different tasks & functions Reproduction o Gonads typically paired o Reproductive ducts open into cloaca o Usually oviparous (egg laying) o Some ovoviviparous (egg laying but egg hatches in parent body) or viviparous (producing living young not hatched from egg) o Fertilization typically external Locomotion o Mostly paired fins are made up of rays & spines o Strong tail is used for most of forward motion Terminal vs ventral mouth Terminal mouth o Mouth in the middle, or centre of the head o Mouth that opens at anterior end of head with upper & lower jaws equal Ventral mouth o Also called a sub-terminal mouth o Mouths located under the fishes head o Lower jaw is shorter than the upper jaw, jaw will often be protrusible o Usually bottom feeders o Often possess barbels that assist in locating food particles o Often seen on species adapted for scavenging or grazing on algae, invertebrates or molluscs o EG the catfish or flatfish like halibut Total Length (TL) The length of a fish as measured from the tip of the snout to the tip of the tail Fork Length (FL) The length of a fish as measured from the tip of its snout to the fork of the tail Oviparous Producing young by means of eggs which are hatched after they have been laid by the parent Oviparous sharks lay eggs, which are protected by an egg case often referred to as a mermaids purse In sharks, the egg is fertilized in the womb and then eggs are laid o The male will insert his clasper into the female's cloaca, releasing sperm & fertilizing her eggs In most oviparous fish, females spawn eggs into the water column, which are then fertilized by males o The eggs are fertilized outside the fish body o Many adults of the same species may come together in a group & release gametes into the water at the same time (spawning) For most oviparous fish, the eggs take less energy to produce so the females release large quantities of eggs In some species of fish, fins have been modified to allow internal fertilisation EGa female Ocean Sunfish is able to produce 300 million eggs over a spawning cycle INTERESTING FACT - Port Jackson sharks carry their egg cases in their mouths o When the Port Jackson shark lays an egg, she'll pick it up in her mouth & screw it into rocks & crevices to anchor it, so that they don't wash away o Gives them interesting shape Ovoviviparous Producing young by means of eggs which are hatched within the body of the parent Embryos develop inside eggs that are retained within the mother's body until they are ready to hatch Unborn young are nourished by egg yolk The mother's body does provide gas exchange (respiration) Pups are sustained & fed by the unfertilised egg yolk as well as by special secretions by the glands in the oviduct walls Once the pups have developed sufficiently inside their eggs, they hatch into the oviduct o Continue to feed off the remaining egg yolk & the gland secretions Once the egg hatches, it remains inside the mother for a period of time & is nurtured from within but not via a placental appendage INTERESTING FACT - intrauterine cannibalism o Embryophagy/ adelphophagy - the largest & strongest embryo actually consumes its womb- mates EG sandtiger shark (Carcharias taurus) o Oophagy - developing embryos feed on a steady supply of tiny, unfertilized eggs o The first pup to hatch will eat the other eggs in the oviduct before they have the opportunity to hatch (only in some shark species) o Grey nurse shark pup will even eat the other embryos of its siblings o Continues throughout embryonic & fetal development = at birth pups have swollen abdomen ("yolk stomach") Viviparous Giving birth to living young that develop within the mother's body rather than hatching from eggs EG bull sharks - gestation period of about 1y & can give birth to 1 - 12 young per birthing Fin spines Many fish species evolved parts of their fins into sharp, spiny, needle-like elements -- called fin spines Function to protect the fish against predators Spines have evolved independently in different lineages - considered evolutionary drivers of fish diversity Gill arch 1 of the several bars of bone or cartilage that occur in pairs with 1 on each side of the throat Support the gills of fishes & amphibians Gill slits Individual openings to gills, which include multiple gill arches & lack a single outer cover Pouches or slits in the front region (pharynx) of the digestive tract in chordates Function in feeding & gas exchange in fishes & some amphibians, but appear during development in all vertebrates Rakers Located inside the oral cavity & point anteriorly from their attachment to the gill arch Prevent debris from entering the fish through the gills (protection of gills) Can also aid in gathering food Branchiostegal rays Series of long, curved & often pointed bones that support the branchiostegal (gill) membrane Branchiostegal membrane The membrane connecting the branchiostegals & enclosing the gill chamber ventrally The membrane below the operculum, often attached to the isthmus, supported by branchiostegals & helping to enclose the gill chamber ventrolaterally Joined to the ventral surface of the body, separating the gill openings Lateral keel A lateral ridge found just anterior to each side of the tail fin on the caudal peduncle of some types of fast-swimming fish Improve the stability of the fish & strengthen the support of the caudal fin Precaudal pits Depression in skin of peduncle at origin of upper & lower tail fin lobes Spiracle In sharks is used to provide oxygenated blood directly to the eye & brain through a separate blood vessel In the rays, the spiracle is much larger & more developed & is used to actively pump water over the gills to allow the ray to breathe while buried in the sand Spiracles are found on most sharks apart from requiem sharks & hammerheads – all of which have to swim constantly Sharks such as nurse sharks & sand tiger sharks which both have spiracles are able to stop swimming Nictitans Thin, tough membrane or inner eyelid in the eye of many species of sharks Covers the eye to protect it from damage, especially just prior to a feeding event where the prey may inflict damage while trying to protect itself Maxilla Functions to push both the premaxilla & the lower jaw forward To open the mouth, an adductor muscle pulls back the top of the maxilla, pushing the lower jaw forward Vomer Flattened, paired, bones forming the anterior part of the roof of the mouth, just behind the premaxillary bones Palatines The palatine bone consists of the perpendicular plate only, lying on the inner edge of the maxilla The lower surface of the bone may bear several teeth, forming a second row behind those of the maxilla o In many cases, these are actually larger than the maxillary teeth Neritic zone The shallow part of the ocean located between the intertidal zone & the oceanic zone Epipelagic Inhabiting the upper zone of the ocean from just below the surface to approximately 100 metres deep Generally enough light penetrates for photosynthesis Pelagic Live & occur in open sea Not close to the bottom or shore Epibenthic Organisms that live on or just above the bottom sediments in a body of water Tend to forage on the creatures that live in or on the sediments Benthic Live at the bottom of a water column – along the substrate The animals & plants that live on or in the bottom are known as the benthos Lunate tail Pointed but not sharply forked Generally some of the fastest fish & can maintain rapid speeds for long durations Produces high lift per drag, achieving high hydrodynamic efficiency at fast swimming speed Protandrous hermaphrodites The changing from the male sex to the female during the growth of the same individual EG clownfish Synchronous hermaphrodites Synchronous hermaphrodites are born with both ovaries & testes Both can produce eggs & sperm at maturity EG salmon & sea bass These fish will form spawning pairs - 1 fish will lay eggs & the other will fertilize them Described on the basis of an anatomical & histological study of the gonads o Although they function simultaneously, the testicular & ovarian parts of hermaphrodite gonads have completely separate ducts o Females & hermaphrodites have the same annual reproduction cycle Batch spawning Females capable of ovulating & spawning multiple batches of oocytes during the individual spawning period An oocytes function in reproductive biology is to fuse with sperm after fertilization, transform into an embryo, then a blastocyst & undergo a process called implantation where it attaches to the wall of the uterus Fish classification examples Paired finned fish divided into 2 classes 1. Class Chondrichthyes – cartilaginous fish o 2 sub-classes ▪ Sub-class Elasmobranchii – sharks & rays Superorder Squalomorphi - squalomorph sharks o Order Hexanchiformes - cow & frilled sharks o Order Squaliformes - dogfish sharks o Order Squatiniformes - angel sharks o Order Pristiophoriformes - sawsharks o Order Rajiformes - batoids Superorder Galeomorphi - galeomorph sharks o Order Heterodontiformes - bullhead sharks o Order Lamniformes - mackerel sharks o Order Orectolobiformes - carpet sharks o Order Carcharhiniformes - ground sharks ▪ Sub-class Holocephali - elephant sharks & chimaeras o Order Chimaeriformes - chimaera & silver sharks 2. Class Osteichthyes – bony fish o 3 sub - classes ▪ Sub-class Cladistia – Polypteridae (one family, in tropical Africa & the Nile) = 14 species ▪ Sub-class Chondrostei - Acipenseridae (sturgeons) & Polyodontidae (paddlefishes) (2 extant families) = 27 species ▪ Sub-class Neopterygii = >32 000 species Whale shark Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharks) Superorder Galeomorphi (galeomorph sharks) Order Orectolobiformes (carpet sharks) Family Rhincodontidae (whale sharks) o Head broad & flattened with huge terminal mouth & minute teeth o Tail fin higher than dorsal fins, lower lobe of tail fin more than half length of upper lobe o Anal fin smaller than 2nd dorsal fin o No fin spines o Eye behind corner of mouth o 5 pairs of large gill slits, last 2 pairs over pectoral fin bases o Gill arches with internal filter screens o Prominent longitudinal ridges on body of adult & distinct lateral keel alongside of peduncle o A single species o Largest fish species in the world – 12m long Monospecific genus Rhincodon Requiem shark Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharks) Superorder Galeomorphi (galeomorph sharks) Order Carcharhiniformes (ground sharks) Family Carcharhinidae (requiem sharks) o 2 dorsal fins without spines o Anal fin present o Lower tail fin lobe 1 third to half length of upper lobe o Precaudal pits (depression in skin of peduncle at origin of upper & lower tail fin lobes) present o 5 pairs of gill slits, last pair over or behind pectoral fin origins o Spiracles small or absent ▪ White sharks are considered obligate ram ventilators, which means they must constantly move in order to move water over their gills to breath o Movable lower eyelid well developed o Mouth extends below eyes o Due to the upturned tail fin of some species, measurements of total length are less accurate than precaudal length (PCL), measured from tip of snout to origin of upper tail fin lobe o Size range 1 – 7.4 m TL o Mainly neritic (the shallow part of the ocean located between the intertidal zone & the oceanic zone), a few species found in rivers & 2 species are truly oceanic o 12 genera, 50 species o EG ▪ Blacktip shark (Carcharhinus limbatus) ▪ Bull shark (Carcharhinus leucas) ▪ Lemon shark (Negaprion brevirostris) Cat shark Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharks) Superorder Galeomorphi (galeomorph sharks) Order Carcharhiniformes (ground sharks) Family Scyliorhinidae (cat sharks) o 2 dorsal fins without spines, 1st dorsal fin origin over or behind pelvic fin origin o Anal fin base longer than 2nd dorsal fin base o Lower tail lobe indistinct o No precaudal pits or pairs of keels o 5 pairs of gill slits, last pair over or behind pectoral fin origins o Nictitans rudimentary (undeveloped/basic form) o Spiracles small, close behind eye o Teeth multi-cuspid, in several functional series & alike in both jaws o Most species oviparous o Size range 30cm – 1.6m o Usually found on or near bottom from shore depths below 2 000m o Small sluggish sharks o Most species restricted to the shallow, cold water, benthic habitats of the southern cape o Warm subtropical habitats act as a barrier to the north act as a barrier to dispersal of catsharks & account for the high degree of endemism in this family o Worldwide in tropical & temperate waters o 17 genera, 100 species, 16 in this area (11 endemic) o EG ▪ Pyjama shark (Poroderma africanum) ▪ Tiger catshark (Halaelurus natalensis) Hammerhead shark Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharks) Superorder Galeomorphi (galeomorph sharks) Order Carcharhiniformes (ground sharks) Family Sphyrnidae (hammerhead sharks) o Head flattened & greatly expanded laterally, with eyes on ends of lateral expansions o 2 dorsal fins without spines o Anal fin subequal to 2nd dorsal fin o Lower tail fin lobe distinct, but upper lobe much longer o Precaudal pits present o 5 pairs of gill slits, last 2 pairs over pectoral fins o Nictitans well developed o No spiracles o 0.9 – 6.1m o Neritic sharks occurring from surface to the bottom shore (around 300m) o Large hammerheads are dangerous & will take speared fish from divers , but they are generally not aggressive o The widely expanded head provides greater manoeuvrability & is used to bash stingrays & hold them against the bottom while shark bites pieces o Hammerheads seem immune to stingray venom o Worldwide in tropical & temperate waters o 1 genus with 8 species, 3 in this area o EG ▪ The great hammerhead (Sphyrna mokarran) ▪ Scalloped hammerhead (Sphyrna lewini) ▪ Smooth hammerhead (Sphyrna zygaena) White shark Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharks) Superorder Galeomorphi (galeomorph sharks) Order Lamniformes (mackerel sharks) Family Lamnidae (white sharks) o Tail fin lunate, lower lobe more than half length of upper lobe o Peduncle flattened, with distinct lateral keels & precaudal pits o 2nd dorsal & anal fins much smaller than 1st dorsal fin o No fin spines o 5 pairs of large gill slits, all in front of the pectoral fins o No nictitans o The modified circulatory system of lamnoid sharks keeps the body temperature warmer than the ambient water temperature & increases the metabolic rate, digestion of food & muscle power o Size range 3 – 7 m, 2 000kg o Swift, epipelagic & epibenthic sharks, occurring from surface to 1 280m o Worldwide o 3 genera, 15 species, 4 in this area o EG ▪ Great white shark (Carcharodon carcharias) ▪ Shortfin mako (Isurus oxyrinchus) ▪ Salmon shark (Lamna ditropis) Ragged tooth shark Class Chondrichthyes (cartilaginous fishes) Subclass Elasmobranchii (sharks) Superorder Galeomorphi (galeomorph sharks) Order Lamniformes (mackerel sharks) Family Odontaspididae (ragged-tooth sharks) o Tail fin upper lobe much longer than lower lobe o 2nd dorsal & anal fins subequal o Anal fin close to tail fin o Body robust, depth about 2x height of 1st dorsal fin o No fleshy feels on peduncle o Upper precaudal pit present, lower absent o No fin spines o Pectoral fins short & broad o 5 pairs of gill slits, last pair in front of pectoral fin origins o Teeth narrow, awl shaped, smooth o Posterior teeth moderately compressed, blade like o No spiracle or moveable eyelid o 3.1 – 4.3m o Benthic & epibenthic on continental shelf & slope, from shore to 1 600m o Worldwide in tropical & warm temperate waters o 2 genera, 3 species, 2 in this area o EG ▪ Sand shark (Odontaspis herbsti) ▪ Sand tiger shark (Carcharias taurus) ▪ Big eye sand tiger (Odontaspis noronhai) Recap – sharks families & common names Rhincodontidae – whale shark Carcharhinidae – requim sharks Scyliorhinidae – cat shark Sphyrnidae – hammerhead shark Lamnidae – white shark Odontaspididae – ragged-tooth shark Family Torpedinidae – Electric (Torpedo) Rays (Order Torpidiniformes) Head, body & pectoral fins forming a flabby circular disc, with large electric organ on each side of head (usually visible through skin on underside of disc) 2 dorsal fins Tail fin with large upper & lower lobes Mouth broadly arched & protrusile Small eyes Spiracles close to eyes Skin naked Teeth small with low cusps Nostril flaps joined into broad short curtain in front of mouth 5 pairs of gill openings on underside of head 0.6 – 1.8m Generally benthic fish on sand, mud bottom, coral reefs & rocky reefs, from shore to 457m Feed on small crustaceans, pelecypods, gastropods, worms, brittle stars & pelagic or demersal fish Powerful electric organs can be used to deliver shock of up to 220 volts – used to deter predators or stun prey Worldwide in tropical & temperate waters 1 genus with 17 species, 3 in this area EG o Common torpedo (Torpedo immaculata) o Marbled electric ray (Torpedo punctata) o Pacific electric ray (Torpedo californica) Family Rhinobatidae– Guitar fish (Order Rhinopristiformes) Head & body flattened but rear part of body shark like Body width at pelvic fin greater than inter orbital width Pectoral fins broadly merging with sides of head 5 pairs of gill slits on underside of head 2 dorsal fins, 1st dorsal fin close to pelvic fins Nostrils in front of mouth Nasal flaps not expanded Ovoviviparous 0.6 – 3.1m Benthic neritic species, from shore to depths of 200m Worldwide in tropical & temperate waters 9 genera, around 53 species, 2 subfamilies in this area EG o Lesser guitarfish (Acroteriobatus annulatus) o Bluntnose guitarfish (Acroteriobatus blochii) o Greyspot guitarfish (Acroteriobatus leucospilus) Family Rajidae – Skates (Order Rajiformes) Head & body depressed, forming a flattened disc with pointed snout & wing like pectoral fins Long, thin tail, usually with 2 dorsal fins near the tip & medial row/rows of enlarged denticles (small tooth-like or bristle-like structure) or thorns Pelvic fins divided into anterior & posterior lobes Nostril flaps not fused to form median nasal curtains 5 pairs of gill slits on underside of head Mouth small, but jaws are powerful with numerous small teeth Adult males have enlarged hooked spines on dorsal surface of disc near outer corners o Spines used to hold female during copulation 25cm – 2.3m TL, 200kg Benthic species on sand or mud bottom Most species on continental slope in 200 – 1 350m, some species occur near shore Feed on crabs, shrimp, hermit crabs, amphipods, isopods, flatworms, polychaete worms, pelecypods, mysids, gastropods, octopus, squid, cuttlefish, bony fish & elasmobranchs Oviparous – eggs laid in tough, flexible, dark brown, keratinous cases Worldwide in tropical to polar seas 9 genera, 220+ species, 4 genera & 25 species in this area EG o Brown ray (Raja miraletus) Family Dasyatidae – Stingrays (Order Myliobatiformes) Head, body & pectoral fins forming flat, rounded or angular disc, width 0.9 – 1.3 times its length Slender tail, usually longer than disc Tail fin absent Dorsal fins absent or reduced to low skin folds on tail Usually 1 or more large, serrate, venomous stinging spines on dorsal surface of tail well behind its base Head in front of spiracles not projecting from disc 5 pairs of gill openings on underside of head 34cm – 2.1m DW, 300+ kg Most species inshore, in estuaries & along sandy beaches, some species in freshwater Larger species more common offshore in 100 – 476 m Feed on pelecypods (bivalve shell), gastropods (slugs & snails), crustaceans, worms & occasionally fish Ovoviviparous Stingrays not aggressive but they use their venomous tail spine defence, when an unsuspecting wader steps on them Wounds can be very painful or even fatal if the victim is struck on the body The wound should be immersed in hot (50 degree C) water for half and hour to destroy the venom & stop the pain Worldwide in tropical & temperate seas 6 genera with 70 species, 14 in this area Family Gymnuridae – Butterfly Rays (Order Myliobatiformes) Head, body & pectoral fins forming a broad diamond shaped disc, much wider than long tail Tail less than half disc length Short spine at base Snout blunt Head flattened, not raised about disc 5 pairs of gill slits on underside of head No dorsal or tail fins 1 – 2.5 m DW Coastal waters over sand or mud Feed on fish, crabs, mole crabs & worms Viviparous Worldwide in tropical & warm temperate seas 2 genera, 12 species, 1 in this area Family Myliobatidae – Eagle Rays (Order Myliobatiformes) Head, body & pectoral fins form an angular (rhomboid) disc much wider than long Fleshy snout & eyes projecting above & in front of leading edge of pectoral fins Spiracles not visible dorsally 5 pairs of gill openings on underside of disc Tail slender, whip-like, with small dorsal fin at base, followed by 1 – 4 serrate venomous spines No tail fin of finfolds Jaws with large, plate like, crushing teeth 1.5 – 2.3 m DW, 200kg Coastal waters over sand, mud, coral & rocky reefs Usually forage at the bottom, using their fleshy snout to root out buried prey from the sediment Feed on crustaceans & thick shelled molluscs, with shell fragments ejected from mouth Swim well above bottom when migrating in enormous schools Sometimes leap high in the air Ovoviviparous (give birth to live young) Worldwide in tropical & warm temperate waters 5 genera, 32 species, 5 in this area Family Mobulidae – Manta Ray (Order Myliobatiformes) Head, body & pectoral fins form an angular rhomboid or chevron disc, much wider than long Head truncate in front, with 2 fleshy paddle like cephalic fins that are normally curled while ray is swimming, but unroll when fish is feeding to direct plankton ( including small fish & crustaceans) into open mouth Eyes & spiracles on sides of head Pectoral fin tips acute, the rear edge concave 5 pairs of gill slits on underside of head Rows of fringed plates over internal gill slits to screen plankton from water flowing over the gills Dorsal fin on base of tail over pelvic fins Tail slender, shorter than disc length Bands of minute teeth on 1 or both jaws 1.1 – 2.7 m DW, 20 kg – 3 tonnes (20 y) Large to enormous, active, strong swimming, filter feeding planktivores of the epipelagic realm Viviparous Worldwide 2 genera, 11 species, 6 in this area Recap – Rays Families & common names Torpedinidae – electric rays Rhinobatidae – guitar fish Rajidae – skates Dasyatidae – stingrays Gymnuridae – butterfly rays Myliobatidae – eagle rays Mobulidae – manta rays Skates vs rays A skate's tail tends to be stockier, whereas a ray's is slender & whip-like Some rays have a stinging spine on the tail, which skates don't have Skates reproduce by laying eggs, rays give birth to live young Class Sacropterygii (lobe finned fish) Bony fish Tetrapods evolved from this group Fins are borne on a fleshy, lobe-like, scaly stalk extending from the body Early limbs foregoing the tetrapods Coelacanth Thought to have gone extinct 65 mya Only known from fossils In 1938 – found off the coast of South Africa 3 sub – classes of class Oesteichthyes Sub-class Cladistia – Polypteridae (one family, in tropical Africa & the Nile) = 14 species Sub-class Chondrostei - Acipenseridae (sturgeons) & Polyodontidae (paddlefishes) (2 extant families) = 27 species Sub-class Neopterygii = >32 000 species Family Muraenidae – Moray Eels Marine Body eel like, cylindrical or compressed No scales or pectoral fins Dorsal fin origin usually before gill opening, but fin is fleshy & origin may be difficult to see Median fins continuous round tail Rear nostril a slit or tube before or above the eye Head pores obvious or indistinct LL restricted to 1 – 3 minute pores before gill opening 25cm – 3.8 m Shallow water, coral & rocky reefs, estuaries, mud or silty sand or sandy bottom from shore to 70 m Morays that feed mainly on fish have long powerful jaws, with numerous sharp canines & some long depressible fangs (fangs can be pushed down) Species that prefer crustaceans have short jaws with nodular or molariform teeth Details of reproduction still unknown for most species Known that some morays are protandrous hermaphrodites & few are synchronous hermaphrodites Morays are not aggressive & rarely bite people Worldwide in tropical & warm temperate waters 15 genera, 200 species, 37 species in this area Family Clupeidae – Herring, Sardines & Pilchards Marine Moderate sized silvery fish Body fusiform or strongly compressed Most species with a keel of scutes along belly Mouth more or less terminal, upper jaw not reach past the eyes Teeth minute or absent Gill rakers usually numerous, long & slender No spines in fins Scales cycloid, usually deciduous No lateral line 6 – 28 cm Most clupeid fish occur in large schools near the surface & many are caught with huge purse seine nets (making them of great economic importance) Juveniles of some species enter estuaries The estuarine round herring can tolerate freshwater Worldwide in tropical & temperate seas 56 genera, 190 species, 50 species occur in fresh water, 13 species in this area Family Ophidiidae – Cuskeels Marine Body tapering to a point, with dorsal & anal fins long, low & joined to the tail fin Pelvic fins absent or of 1 -2 slender rays Scales small & cycloid Oviparous 16 cm – 1.6 m Most species in deep water Worldwide 46 genera, 209 species, 23 in this area Family Syngnathidae– Seahorses & Pipefish Marine Body armoured with dermal plates forming tubular series of rings No scales Mouth small, terminal, usually at end of tubular snout No teeth Gill opening a pore above opercle, which is almost completely joined to head by skin Gills lobate Head length is from tip of upper jaw to rear edge of opercle Snout length is from tip of upper jaw to front edge of eye socket Sexually dimorphic – male carry fertilized eggs exposed or concealed within ventral pouch or folds of skin 2 – 65 cm Worldwide in tropical & temperate seas Most species marine, but some also found in estuaries & freshwater 52 genera, 215 species, 25 in this area Seahorse vs pipefish Both pipe fish & seahorse have small, bonnie, narrow noses & a small fin on their back to help them swim The pipe fish is long, has a fairly straight body with a thin tail, end of most pipe fishes is a small but useful fin that helps them swim fast The sea horse has an extended belly & a curled up tail The seahorse has 2 small fins on the top of its head to help turn through the water (pipe fish doesn't) Often don’t live in the same habitat as they outcompete each other (both have similar diets & live in shallow waters = competition) – EG there are no pipe fish where the Fauna seahorse lives because they wouldn't be able to compete with it Male sea horse bears the unborn offspring o Female deposits 1500 eggs into the males pouch o 9-45 days baby seahorses immerge small but fully developed Female pipefish fight over the male (otherwise similar to seahorse – males ) Family Serranidae – Rockcods, Goldies, Seabasses & Soapfish Body robust or somewhat compressed, oblong to elongate Dorsal fin with 7 – 13 spines, 10 – 21 rays Anal fin with 2 -3 spines, 6 – 10 rays Pelvic fin with 1 spine, 5 rays Tail fin rounded, truncate to deeply forked Maxilla exposed Small slender teeth on jaws, vomer & palatines Small canines usually present at front jaws No molars or incisors Preopercle serrate (serrations reduced in adults of some species) Opercle with 3 flat spines, upper & lower spines often indistinct (covered by skin & scales) Scales small to moderate, adherent, usually ctenoid Cheeks & opercle scaly LL usually complete Branchiostegal rays 7, membranes separate, joined to isthmus far forward 4 cm – 2.7 m Coral & rocky reefs from shore to 500m Some species occur in estuaries, tide pools, mangrove swamps & over sandy/mud bottom All serranids are carnivorous, but variety of ecological types (in subfamilies) Most species are protogynous hermaphrodites, but synchronous hermaphrodites also common Worldwide in tropical & warm temperate waters 5 subfamilies 48 genera, 330 species, 77 species in this area Family Haemulidae – Rubberlips & Grunters Marine Body oblong, slightly compressed Dorsal fin with 9 – 14 spines, 13 – 25 rays Anal fin with 3 spines, 6 – 13 rays Tail fin truncate to emarginate Maxilla hidden when mouth is closed Jaws with a series of small teeth, no molars or canines, no teeth on vomer or palatines Preopercle serrate Opercle ends in a blunt flat point Scales small to moderate, weakly ctenoid Diurnal predators (hunt during the day) of shallow waters Adults feed mainly on benthic invertebrates by taking in mouthfuls of sand & expelling the sediment out their gill openings 20 cm – 1 m Worldwide in tropical & temperate waters 18 genera, 120 species, 19 in this area Family Lutjanidae – Jobfish & Snappers Body oblong or elongate Dorsal fin continuous with 10 – 12 spines, 10 – 16 rays Anal fin with 3 spines, 7 – 11 rays Pelvic fins with 1 spine, 5 branched rays & scaly axillary process at base Tail fin truncate to distinctly forked Upper edge of maxilla partly covered by preorbital bone when mouth is closed Jaws usually with more or less distinct canines at front Vomer & palatines generally with small conical teeth Opercle ends in 1 or 2 blunt points Preopercle serrate Scales ctenoid Cheek & operculum scaly Snout, preorbital & lower jaw naked 33 cm – 1.3 m Most species diurnal demersal fish of coral & rocky reefs 3 – 550 m Lutjanids excellent eating fish (NB in sport & commercial fisheries) Tropical & warm temperate waters of all oceans 13 genera, 105 species, 26 in this area Family Sparidae – Seabreams & Porgies Body oblong, slightly compressed 1 continuous dorsal fin with 10 – 13 spines & 8 – 16 rays Anal fin with 3 spines & 8 – 15 rays Last dorsal & anal fin rays divided to their base but counted as a single ray Pelvic fins with 1 spine & 5 rays Tail fin emarginate to forked Maxilla mostly hidden when mouth is closed Posterior tip of maxilla with a groove, into which the tip of the premaxilla fits forming a unique lateral joint of upper jaw bones Teeth conical or incisiform (compressed) Most species with molar teeth Some species with enlarged canines or incisors at front of jaws No teeth on vomer, palatines or tongue Preopercle edge smooth Opercle ends in blunt flat point Scales small to moderate, weakly ctenoid Opercles & cheeks scaly 30 cm – 2 + m Occur in rocky & sandy areas near shore or offshore reefs to 450 m A few species are typically found in estuaries Many sparids occur in large schools, others are usually seen singly or in small aggregations Diumal fish that feed on algae &/or a variety of prey Eggs & larvae pelagic (except for steentjie which lay eggs in a depression on sandy bottom) Sparid fish occur in temperate & tropical waters, but most species are restricted to temperate continental areas At oceanic islands, the sparid niche seems to be occupied by the emperors (family Lethrinidae) & wrasses Most sparids are NB food fish – major component of line caught fish in commercial & sport fisheries of SA Larger species grow slowly & adults are territorial with small home ranges, making them vulnerable to overfishing Worldwide 29 genera, 100 species, 41 species in this area Family Dichistiidae – Galjoen Marine Body compressed Head (except front of snout), body & fins covered with small firmly adherent ctenoid scales Dorsal fin with 10 spines, 18 – 23 rays & deep notch before soft rayed part Anal fin with 3 spines, 13 – 14 rays Soft dorsal & anal fins with high lobe anterioirly Pectoral fins shorter than or subequal to head Pelvic fins with 1 spine, 5 rays Tail fin shallowly forked Maxilla reaching below front half of eye Lips thick Jaws with outer row of strong curved incisors, small teeth behind Molars on pharyngeal bones but no teeth on roof of mouth Inter – orbital width greater than eye diameter Preopercle serrate Branchiostegal membranes joined to isthmus 32 – 80 cm NB sport fish, caught by shore anglers in mixed rocky/sand areas Comprises of 2 species restricted to southern Africa & Madagascar Family Sciaenidae – Kob, Geelbek & Baardman Marine Body oblong to slightly elongate, somewhat compressed, with moderate cycloid or ctenoid scales 2 contiguous dorsal fins, the 1st of 9 – 11 slender spines, 2nd dorsal fin with 1 spine, 22 – 31 rays Anal fin with 2 spines, 6 -9 rays Tail fin rounded, truncate or concave Pelvic fins with 1 spine, 5 rays & no scaly axillary process Mouth terminal or subterminal, maxilla more or less hidden by preorbital bone when mouth is closed Jaws with small conical teeth Canines present in some species No teeth on palate or tongue Preopercle smooth 1 -2 flat blunt spines on rear edge of opercle Opercle & cheek scaly, snout naked Branchiostegal membranes free from isthmus Swim bladder well developed, carrot shaped, hammer shaped or anchor shaped, with various diverticular Peduncle length is measured from dorsal fin base to LL scale at tail fin base Lateral line extends to end of tail fin 23 cm – 2 m Sciaenids generally prefer shallow sandy areas & often found in estuaries Larger species economic NB as food Also called croakers or drums because they can produce a variety of sounds by means of muscles that vibrate the gas filled swim bladder Tropical & temperate waters of all oceans 70 genera, 100 + species, 11 in this area Family Chaetodontidae – Butterfly fish & Coachmen – pronounced key-to-don Marine Body deep, oblong or disc like, strongly compressed Body depth usually greater than head length Dorsal fin continuous with 11 – 18 strong spines & 14 – 28 rays Anal fin with 3 – 4 spines & 13 – 23 rays Soft dorsal & anal fins large, reaching to or beyond base of tail fin Pelvic fins with 1 spine, 5 rays Pectoral fins with 14 – 19 rays, not longer than head Scales moderate to small, ctenoid, covering head & body LL inconspicuous No enlarged spine at corner of preopercle Nostrils minute, close together Mouth small with small slender teeth 10 – 47 cm Common & conspicuous reef fish at depths of 1 – 250 m Coral polyps in diet of many species Also feed on small benthic invertebrates (worms, crustaceans, molluscs) & algae or zooplankton Usually occur in pairs, some are solitary but others form large groups Their diurnal (active by day) habits & distinctive bright colours (mainly yellow, white & black patterns) make them easy to identify At night, most butterfly fish usually change colour & retreat into crevices or caves to sleep Worldwide in tropical & warm temperate seas 11 genera, at least 124 species Family Carangidae – Kingfish, Leervis, Queenfish etc Marine Body shape variable, deep & compressed to elongate & fusiform Scales small & cycloid Some species with posterior LL scales modified as enlarged, spiny scutes (thickened bony scales with a keel or spiny point) Jaws usually with small teeth in rows or bands or a single row of moderate to large canines Teeth absent in adults of some species Dorsal fin usually divided into separate spinous & soft – rayed fins or spinous fin is very low, with 4 - 8 spines (spines rudimentary or embedded in adults of some species EG Alectis) Anal fin with 3 spines, 1st 2 spines set well in front of fin Anal fin spines not visible (embedded) in adults of some species Tail fin forked The usual length measurement for carangid fish is fork length (FL) measured from front of upper jaw to end of middle tail fin rays Juveniles are often difficult to match with adults because of considerable changes in body, shape & colour patterns with growth 25 cm – 1.9 m FL Caragids occur in variety of habitats: coral & rocky reefs, in the surf along sandy beaches & in estuaries Some juveniles are typically found riding the bow wave in front of sharks & large bony fish, or are associated with jellyfish or flotsam in the open ocean Many species occur in large schools & have economic NB in trawl or purse seine fisheries Most are swift predators Found in tropical & temperate waters of all oceans 32 genera, 143 species, 54 in this area Family Scombridae – Tuna, Mackerel & Bonito Marine Body robust, oblong or elongate & fusiform, moderately compressed in some gena Snout pointed, upper jaw not protrusile Maxilla slips under preorbital bone when mouth is closed Teeth large, moderate or small 1st (spinous) dorsal fin usually short, separate from soft rayed fin & depressible into a groove Row of finlets behind dorsal & anal fins Tail fin lunate & stiff, with 2 short fleshy keels at base (some species with additional longer keel along side of peduncle) Pelvic fins with 6 soft rays Body covered with small to moderate scales or with an area of embedded thick scale behind the head & around the pectoral fins called a corselet & the rest of the body without scales or with minute thin scales Swimbladder present or absent FL used as measurement 38 cm – 3 m Fast swimming voracious predators of the epipelagic zone of open ocean Several species also occur in coastal waters Most feed on a variety of pelagic fish, squid & crustaceans, very few species eat primarily zooplankton Some tunas can maintain their body temperature several degrees above ambient water temperature – elevated body temperature increases the efficiency of the swimming muscles, especially during excursions into cold water below the thermocline Don’t change sex & there’s no obvious difference between sexes Batch spawning occurs in tropical & subtropical areas, often near shore Eggs & larvae are pelagic Many species occur in large schools & are migratory Some tuna species make cross ocean migrations Scomberomorus species make coastal migrations Economic NB food fish (often eaten in raw sushi as harbour few parasites) Caught with purse seine, drift nets, longlines, hook & line (live bait) or trolling lure or bait at surface Worldwide in tropical & temperate seas 15 genera, 51 species, 18 in this area Family Istiophoridae– Sailfish, Marlin & Spearfish (also known as bill fish) Marine Body elongate, fusiform, somewhat compressed anteriorly In adults, snout & upper jaw greatly elongate, forming bony spear like pointed rostrum (beaklike protection) In juveniles less than 30 cm SL, jaws are equal Jaws with minute file like teeth 1st dorsal fin base longer than height of fin & contiguous with short 2nd dorsal fin 1st anal fin clearly separate from lower 2nd anal fin Tail fin lunate, with 2 short fleshy keels on each side of base Pelvic fins reduced, ribbon like, with 1 spine & 2 fused soft rays 1st dorsal fin & anal & pelvic fins fold into grooves when fish is swimming rapidly Branchiostegal membranes united, free from isthmus No gill rakers Body covered with small elongate embedded scales 2.3 – 4.5 m FL (including bill) Large swift voracious predators of the epipelagic zone of the open ocean Feed mainly on a variety of pelagic fish, squid & crustaceans Some species also forage at the bottom (feeding on demersal species) Prey are swallowed head 1st , usually after being stunned or killed by a powerful blow from the bill Long bony bill is used to strike fish in order to impale, disable or kill the prey before eating it Usually strike prey with a lateral slashing movement of the bill, particularly efficient in a tight school of bait fish Bill also used in defence against mako & great white sharks Some species maintain their body temperature several degrees above ambient water temperatures (like large tunas) – elevated body temperature increases efficiency of the swimming muscles, especially during excursions into cold water below the thermocline Done change sex & except for size (females usually larger), there are no obvious differences between sexes Spawning occurs in tropical & subtropical areas, often near shore Eggs & larvae are pelagic Great demand as food fish in Japan & other Asian countries Worldwide in tropical & temperate seas 3 genera, 11 species, 7 in this area RECAP Families & common names – Marine fish Muraenidae – moray eels Clupeidae – herring, sardines, pilchards Ophidiidae – cuskeels Syngnathidae – seahorses, pipefish Serranidae – rockcods, goldies, seabasses, soapfish Haemulidae – rubberlips, grunters Lutjanidae – jobfish, snappers Sparidae – seabreams, porgies Dichistiidae – Galjoen Sciaenidae – kob, geelbek, baardman Chaetodontidae – butterfly fish, coachmen Carangidae – kingfish, leervis, queenfish Scombridae – tuna, mackerel, bonito Isthiophoridae – sailfish, marlin, spearfish Family Protopteridae – African lungfishes Freshwater Elongate & soft bodied with long soft dorsal & anal fins joined to form a pointed tail Paired thread like pectoral & pelvic fins & cloaca offset to1 side Python like head has prominent lateral line canals Up to 600 mm TL Lives in swamps, temporary pans & slow flowing rivers Breathes air, surviving habitat desiccation by burrowing & forming cocoon in mud Preys on molluscs & other slow moving invertebrates, fish, tadpoles & frogs Males guards the nest Family Anguillidae – Freshwater eels Freshwater A long & sinuous eel, with large mouth, sharp teeth, soft skin & minute scales The dorsal, caudal & anal fins are confluent (merge) Lacks pelvic fins Reaches 1.2 m TL Nocturnal, living in crevices & between rocks or buried in soft sediment Preys on aquatic insects & invertebrates (larger individuals preys on crabs, frogs & fish) Male remains in fresh water for 8 – 10 years, Female 15 – 20 years Family Cyprinidae – Barbs, yellowfishes & labeos Freshwater Largest vertebrate family, with nearly 3 000 described species (150 occur in southern Africa) Have a Weberian apparatus (like catfish & characins) – a complex modification of the 1st few vertebrae to form a connection between swim bladder & inner ear o Detects sounds & pressure waves Polyploidy (multiple sets of chromosomes) is characteristic of southern African species Family Alestidae – Robbers & Tiger Fish Freshwater Characterized by their strong jaws & sharp teeth Active midwater swimmers EG Tigerfish (Hydrocynus vitatus) o Spindle shaped, with large bony head o Prominent jaws with exposed interlocking canine teeth o Deeply forked tail o Silver-blue with a series of semi parallel black stripes along flanks & upper body o Reaches 700 mm SL o Shoal in open water, actively hunting & pursuing prey o Small juveniles feed on insects o Adults progress to a fish diet & become so strong & agile that they even take swallows in flight o Worn & broken teeth replaced throughout life o Breed in rain swollen rivers during summer, moving upstream & spawning in mass over flooded margins & rocky runs Family Clariidae – Air-breathing catfishes Freshwater Large family of 118 species, 3 genera & 8 species in this area Widespread in tropical Africa & southeast Asia Breath using a tree like accessory air breathing organ situated in a chamber above gill arches EG Sharptooth catfish (Clarias gariepinus) o Body laterally compressed towards tail o Head large, heavy & flattened o Eyes near front o 4 pairs long slender barbels o Mouth large, with broad band of fine teeth in each jaw o Pectoral fins with serrated spine o Well developed air breathing organ in chamber behind head o 1.4 m SL & 50+ kg o Favours floodplains & marshes o Survives habitat desiccation by breathing air & can move over land between pools at night o Forages alone or in groups o Omnivorous, taking plankton, larger invertebrates & aquatic & terrestrial vertebrates o Mass in large groups to breed on shallow, flooded, grassy margins of lakes & rivers o Fast growing o Long lived o Africa’s most wide spread fresh water fish Family Mocchokidae – Squeakers, suckermouth catlets Freshwater The largest African family of catfishes – 200 + recognized species 2 genera in southern Africa o Synodontis – known as ‘squeakers’ for the rasping sound they make when removed alive from the water o Chiloglanis – known as ‘suckermouths’ for their disc like mouths EG Largespot squeaker (Synodontis macrostigma) o Short stout squeaker o Barbels on jaws have stubby branches o Large dark brown or black spots cover body o 170 mm SL o Nocturnal, resting in a sheltered place during daylight o Omnivorous – forages on bottom sediments, eating plants, snails & small fish o Related species: Upper Zambezi Squeker (S. woosnami) from upper Zambezi & Okavango systems differs in pigmentation (small spots & vermiculations) & teeth Family Cichlidae – Cichlids Freshwater 1 700 species 12 genera & 45 species in southern Africa Tropical – from South & Central America, Africa, Madagascar & India Spiny rayed Have spines in dorsal & anal fins Single nostril Split lateral line Strong pharyngeal (throat) bones with teeth Breeding behaviours are varied & complex Associated colour patterns in males often NB taxonomic features RECAP Families & common names – Freshwater fish Protopteridae – African lungfishes Anguillidae – freshwater eels Cyprinidae – barbs, yellowfishes, labeos Alestidae – robbers and tiger fish Clariidae – air-breathing catfishes Mocchokidae – squeakers, suckermouth catlets Cichlidae – cichlids FISH BREATHING Chondrichthyes All chondrichthyans breathe through 5 - 7 pairs of gills, depending on the species Water moves over the gills from: o Mouth o Spiracles ▪ Pairs of openings behind the eyes that opens to the buccal cavity (mouth cavity) ▪ Draws oxygenated water in Pelagic sharks – ram ventilation or buccal pumping o Pelagic = water column of the open ocean, absence of spiracles o In general, pelagic species must keep swimming to keep oxygenated water moving through their gills o Ram ventilation = extraction of oxygen during the passage of water over the gills owing to motion through the water rather than active, muscular pumping (must constantly move in order to move water over their gills to breath) Benthic sharks – buccal pumping or action of spiracles o Benthic = bottom of water bodies, have spiracles o In general, benthic species can actively pump water in through their spiracles & out through their gills o Spiracles act like a straw drawing water over their gills and out the gill slits o Many of these sharks make obvious use of this technique by lying completely still on the seabed, sucking water in through spiracles so that they can keep their mouths closed while breathing Buccal pumping = sharks lower their bottom jaw to draw oxygenated water into the mouth, then raise it to push the oxygen-rich water over their gills o Often used by non active swimmers EG nurse sharks O2/CO2 diffuses in/out of blood capillaries in gill filaments (see Osteichthyes) o Within the gill filaments (highly branched & folded = more surface area), capillary blood flows in the opposite direction to the water that’s flowing over the gills, causing counter-current exchange ▪ Counter current system is the most efficient method of exchanging oxygen & carbon dioxide between the water and blood o Blood in the capillaries picks up oxygen that's dissolved in the water o Circulatory system can then carry the oxygenated blood to the other parts of the body o The gills push the oxygen-poor water out through openings in the sides of the pharynx Absence of lungs (use gills to filter oxygen from the water instead) Osteichthyes Operculum present Mouth & gill chamber create suction & pump action (buccal pumping) Water in though mouth, over gills, out through gill slits Water enters the gill chamber through a fish's mouth & exits through gill openings under the operculum Blood flowing through the gill filaments absorbs oxygen from the water O2/CO2 diffuses in/out of blood capillaries in gill filaments Some fish have adaptations for getting oxygen from air o Lungfish must return to the surface to breathe air General - The water over the gills & the blood in the gills forms a counter current system Gills contain many filaments(each with thousands of tiny folds called lamellae) = increase surface area that comes into contact with water Dissolved oxygen in seawater passes through thin membranes in the lamellae & enters the fish's blood While bony fishes have 1 gill opening on each side of its body, sharks have 5 - 7 The gills of bony fishes are also hidden behind flaps that open & close, whereas sharks have exposed gill slits Fish buoyancy Buoyancy – the ability to float Gravity causes sinking if no buoyancy mechanisms present Swim bladder - hydrostatic organ that maintains buoyancy o Internal gas-filled organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy o = ability to stay at their current water depth without having to expend energy in swimming Sharks & rays Swim bladder absent - other mechanisms include: o Enlarged liver filled with oil (called squalene) ▪ Oil is less dense than water which allows it to float on top of water ▪ The oil in sharks liver causes sharks to want to float instead of sink, since oil is less dense than water ▪ The oily liver is also used for other daily functions such as digestion ▪ This large, soft & oily organ can comprise up to 25% of the total body weight ▪ Interesting fact - Shark liver oil is used along with usual cancer drugs to treat leukemia & other cancers,to prevent radiation illness from cancer X-ray therapy, to prevent the common cold, flu & swine flu & to boost the body's immune system (unfortunately most desirable squalene comes from deep-sea sharks, which are also among the most vulnerable of species) o “dynamic lift” – great white sharks ▪ The shark uses its large pectoral fins which are situated on either side of its body to create lift beneath them – almost like the wings on a plane o Swim to prevent sinking – energy demanding: ▪ Pelagic sharks – heterocercal tail (2 asymmetrical lobes) Heterocercal tail pushes water postero-ventrally, generating both thrust & lift The upper lobe of the caudal fin produces the most thrust & at least some of that would tend to force the shark downwards ▪ Pelagic rays – pectoral fins Swim bladders Basically like an air-inflated balloon that can expand & contract depending on how much gas is inside When the swim bladder expands it will increase in volume & therefore displace more water o This increases the fish's buoyancy & it will float upward Fish can inflate the swim bladder by gulping atmospheric air from the surface of the water & passing it through this connection Deep water fish that do not encounter the surface of the water = have a single chambered swim bladder (physoclistous) that is regulated by the circulatory system In some fishes, the gas inside the swim bladder is obtained by surface gulping In most the swim bladder is filled under pressure with gases, mainly oxygen, from the blood via active diffusion & actions of the gas gland Air less dense than water! 2 basic types of swim bladders in Bony fish Physostomous – shallow water o Directly connected via pneumatic duct to the gastrointestinal tract o Fish must “gulp” air to inflate their swim bladder & “burb” or “fart” air to deflate them o Connected to oesophagus o Gas filled & released – oesophagus o EG bowfins, carps, trout, catfish, some eels o Pneumatic duct = the duct that connects the air bladder with the alimentary canal (digestive tract) in physostomous fishes Physoclistous – deep water o Not connected to oesophagus (fish lose the pneumatic duct in the adult phase = no connection to oesophagus) o Fish must diffuse gas from the blood to fill & collapse swim bladder o Filled with gas – rete-mirabile & gas gland ▪ A counter current system (the rete mirabile) is used to concentrate gases for the filling of the swim bladder under elevated hydrostatic pressure o Gas release - ovale ▪ Specific structure called ovale that is used to remove the gases from the swim bladder Fish osmoregulation Why can freshwater fish not survive in seawater & vice versa? o Related to osmoregulation ability of each group Osmoregulation - the regulation of water & salts (solutes) in the body o Process of maintaining salt & water balance (osmotic balance) across membranes within the body Osmotic pressure – measure of the tendency of water to move into one solution from another by osmosis o The minimum pressure applied to a solution to stop the flow of solvent molecules through a semipermeable membrane Osmosis – spontaneous movement of water or other solvents through a semi-permeable membrane Hypertonic – a solution with a higher osmotic pressure than another, higher concentration of solutes o Solution that contains more dissolved particles than is found in normal cells & blood o Any external solution that has a high solute concentration & low water concentration compared to body fluids Hypotonic – a solution with a lower osmotic pressure than another, lower concentration of solutes o Lower concentration of solutes than another solution o Saltwater fish are hypoosmotic to the sea, their blood has a lower solute content = a lower osmotic pressure (about 400 mOsmol) than sea water (about 1000 mOsmol) o = a passive loss of water at the gills & a passive gain of salts Osmolality of fresh water, sea water & fish blood o A measure of the concentration of chemical particles found in the fluid part of the blood Concentration of water inside the cells of fish might be different than the concentration of water outside the fish Relative concentrations of water & solutes internally must be maintained (with narrow limits) How do fish regulate osmotic pressure? o They absorb a controlled amount of water through the mouth & the gill membranes o Due to this intake of water, they produce large quantities of urine through which a lot of salt is lost o The salt is replaced with the help of mitochondria-rich cells in the gills Homeostasis = tendency towards a stable internal environment by adjusting to external conditions o Defined as a self-regulating process by which a living organism can maintain internal stability while adjusting to changing external conditions o Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney o The kidney, gills & skin NB in maintaining a fish's internal environment & checking the effects of osmosis o Fish need to be able to regulate the amount of water & salt in their systems in order for all of their cells to function Cells require a balance between uptake & loss of water Excretion -> gets rid of nitrogenous metabolites & other waste products Osmoregulators - expend energy to control water uptake & loss in a hypertonic or hypotonic environment o Organisms that actively regulate their osmotic pressure (& salt concentrations), independent of the surrounding environment o Most freshwater fish Osmoconformers- only some marine animals, are isotonic (same osmic pressure) with their surroundings & do not regulate their osmolarity o Maintain an internal salinity similar to their ambient conditions o EG most marine invertebrates, seagrass etc o Hagfish, skates & sharks Osmoregulation – fresh water bony fish Hypertonic in a hypotonic environment o Fish is hypertonic to its environment, meaning the fish is "more salty" & water continually flows into the fishes body via osmosis o The concentration of salt is higher in their blood than their surrounding water Water diffuses in, salts out Constantly take in water Lose salts by diffusion Kidney retains salts o Freshwater fish have very efficient kidneys that excrete water quickly Need not drink water High quantity dilute urine o Reabsorb salt from their urine before it is ejected to minimize losses Salts lost are replaced by foods & uptake through gills o Actively take salt from their environment using special cells in the gills Osmoregulation – marine bony fish Hypotonic in hypertonic environment o Fish is hypotonic or "less salty" compared to its environment, meaning water continually flows out of the fish's body o With the exception of hagfish, fish maintain osmotic concentrations of body fluids at levels roughly 1/3 of seawater Water diffuses out, salts in Constantly lose water o Osmotic challenge faced by marine bony fish = they inhabit an environment that has a very high salt concentration o Means that they could easily lose water from their bodies through osmosis, as their internal environment has a lower concentration of solutes than that of their surroundings o Can only drink seawater to prevent osmotic dehydration & maintain water balance = concentrated urine to get rid of salts & conserve water Kidney retains water Drink water o To compensate for the constant loss of water through osmosis, they have to drink a lot of water & secrete excessive salt from their gills to the surrounding seawater Low quantity concentrated urine o Urine output is considerably reduced to conserve water Gain salts by diffusion & food Excrete salts through gills Osmoregulation – sharks & rays Unlike fish, sharks & rays match the concentration of dissolved particles in their body fluids to seawater, retain a waste product (urea) to maintain this osmotic balance (= osmoconformer) o Isotonic with their surroundings o Have rectal glands that help in the regulation of osmotic pressure Retain urea (2% versus 0.01% in bony fish) o The urea—the non-toxic nitrogen-containing substance which humans excrete in their urine—keeps the fish from drying out in salty seawater o To keep from losing water & dehydrating in the salty sea, sharks maintain high levels of urea o Because of the presence of urea in blood, sharks become hypertonic in comparison to marine water this allows them to swim freely in the marine water without the fear of dehydration Generating lots of the chemical urea = counterbalances the salt in the ocean water Hypertonic therefore similar to bony fish in fresh water Water absorbed through gills & skin Ingests salt with food Salts excreted by urine 35% saltwater salinity & 35 % fish salinity Sharks (along with amphibians & coelocanths) are osmoconformers & ion regulators (urea) Their body fluids are almost the same concentration of solutes as seawater, but they use different solutes o They maintain an equal or isotonic salt concentration with the surrounding water o They have rectal glands that help in the regulation of osmotic pressure Sharks do have to deal with a slight influx of salt, which is excreted by a rectal gland 1 of the ions that sharks use is urea Urea is relatively easy to produce (most organisms al

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