Ecdysozoa and Nematoda

Ecdysozoa

• Protostomes possess a cuticle, a non-living outer layer secreted by the epidermis.
• The cuticle is a stiff, hardened outer body wall that restricts growth and must be molted via ecdysis.
• Ecdysozoans, like roundworms and arthropods, molt cuticle as they grow.
• Molting is regulated by the hormone ecdysone.
• Ecdysozoans do not share the same body plan.
• Nematoda, Nematomorpha, and Kinorhyncha members are pseudocoelomates.
• Nematodes, kinorhynchs, and priapulids use their pseudocoelom as a hydrostatic skeleton.
• Loricifera species vary from being pseudocoelomate and acoelomate.
• Panarthropoda contains arthropods, onychophorans, and tardigrades, which have coelomate bodies, but their body cavity size is reduced.

Nematoda (Roundworms)

• Nematodes are the most important pseudocoelomate animals in abundance and impact on humans.
• They are found worldwide in soil, oceans, freshwater habitats, plants, and animals.
• About 25,000 nematode species have been described, and as many as half a million species may exist.
• Soil can contain billions of nematodes per hectare.
• Nematode parasites are found in nearly all animal and plant species, making nematode infestation studies important in agriculture and biomedical sciences.

Parasitic Nematodes: Hookworms

• Hookworms are small worms with hook-like curves at their anterior ends.
• Sexes are separate, with males being smaller.
• Large plates in the mouth cut into the intestinal mucosa and suck the host’s blood.
• Blood is pumped through the intestines, partially digesting it and absorbing the nutrients.
• Heavy infections can cause anemia because hookworms suck more blood than they digest.
• Children can suffer mental retardation, stunned growth, and lack of energy.
• Eggs pass out in feces, and juveniles hatch in the soil and live on bacteria.
• Infective juveniles burrow through human skin to get to the blood vessels.
• They travel in the blood to the lungs, are coughed up, swallowed, and go to the stomach and intestines.
• Juveniles mature in the intestine.

Parasitic Nematodes: Trichinella

• Trichinella spiralis causes trichinosis.
• Adult worms burrow into the intestinal mucosa, and females directly produce juvenile worms.
• Juveniles penetrate blood vessels and circulate throughout the body to all tissues and spaces.
• They penetrate skeletal muscle cells and become one of the largest intracellular parasites.
• Juveniles redirect gene expression of host cell musculature, where cells lose striations and become nurse cells to the parasite.
• When poorly cooked meat containing encysted juveniles is eaten, worms are liberated and mature in the host intestine.
• Trichinella sp. can infect humans, hogs, rats, cats, and dogs.
• Hogs can become infected when eating uncooked scraps of infected meat or infected rats or their droppings.
• T. spiralis has four other sibling species with variable distribution, infectivity to various hosts, and freezing resistance.
• Heavy infections cause death, but lighter infections are more common worldwide.

Parasitic Nematodes: Filarial

• Eight species of filarial nematodes infect humans, and some cause serious diseases.
• Wuchereria bancrofti and Brugia malayi infect more than 120 million people in tropical areas and are known as "elephantiasis."
• They cause inflammation and blockage of the lymphatic vessels.
• Females release live young, tiny microfilariae, into blood and lymph.
• Mosquitoes (intermediate host) ingest microfilariae when they feed on infected animals.
• These develop to infective stage and move into another host when the mosquito feeds again.

Nematodes in the Environment

• Free-living nematodes have a fundamentally important role in the environment as nutrient recyclers.
• They are decomposers who make nutrients available to other organisms.

Take Home Message (Nematodes)

• Wash your hands before you eat.
• Cook your food well.
• Avoid eating dirt.
• Drug treatments are available if you forget to do any of the above.
• Nematodes have only longitudinal muscle, antagonist pairing, and a hydrostatic skeleton (pseudocoel).
• Parasites migrate in the body, and have direct or indirect life cycles with 4 examples.
• Free living nematodes are nutrient cyclers

Arthropoda: Web Spinning Habits

• Spiders have 2-3 pairs of spinnerets containing microscopic tubes that run to silk glands.
• The silk producing apparatus in the abdomen involves glands that secrete liquid silk which passes to spinnerets and out spools & spigots to outside.

Spider Silk

• Spider silk is "5x Stronger than steel and twice as elastic as nylon!"
• Spider silk has a high tensile strength (stretch without breaking).
• Spider silk is the strongest of any natural material.
• Spider silk is a fibrous protein.
• Six different types of glands produce different kinds of silk.
• Silk differs in diameter & qualities, and is used for different functions like orb webs, safety/climbing lines, nests, cocoons, traps, prey storage, eggs sacs, sperm platforms & burrow linings.

Are Spiders Really Dangerous?

• Most people fear spiders without good reason, because spiders are allies of humans in our battle with insects.
• American tarantulas rarely bite, and their bite is not dangerous.
• Black widow spiders are dangerous because their venom is neurotoxic.
• The brown recluse spider has hemolytic venom that destroys tissue around the bite.
• Some Australian and South American spiders are the most dangerous and aggressive.

Order Scorpionida: Scorpions

• Scorpions are more common in tropical and subtropical zones but occur in temperate areas.
• Approximately 1,400 species exist worldwide.
• They are nocturnal and feed largely on insects and spiders.
• Sand-dwellers locate prey by detecting surface waves (vibrations) with leg sensillae.
• Scorpions are ovoviviparous or viviparous and produce from 6 to 90 young.
• Scorpions perform complex mating dances.
• Appendages (chelicerae, pedipalps, and 4 pairs of walking legs) are attached to the cephalothorax.
• Pedipalps are used for catching prey.
• They have a pair of medial eyes and 2–5 lateral eyes.
• The preabdomen has 7 segments.
• The postabdomen has a long, slender tail of five segments that ends in a stinging apparatus.
• The stinger on the last segment has venom that varies from mildly painful to dangerous.

Order Acari: Ticks and Mites

• Ticks and mites are medically and economically the most important arachnids.
• About 30,000 species have been described which may be up to 500 000 to 1 million species.
• They are both aquatic and terrestrial and inhabit deserts, polar areas, and hot springs.
• Most mites are less than 1 millimeter long.
• Ticks may range up to 3 cm due to distension from feeding.
• Unlike other arachnids, they have complete fusion of the cephalothorax and abdomen.
• There is no sign of external segmentation.
• Adult mites and ticks possess 4 pairs of legs.

Important Mites

• House dust mites are free-living and often cause allergies.
• Spider mites are important agricultural pest mites that suck out plant nutrients.
• Chiggers (larval Trombicula mites) feed on dermal tissues and cause skin irritation.
• Hair follicle mite Demodex is harmless, but other species cause mange in domestic animals.
• Human itch mites burrow into the skin and cause intense itching (scabies).
• Tick species of Ixodes carry Lyme disease (bacteria), which is debilitating if untreated.
• Tick species of Dermacentor transmit Rocky Mountain spotted fever (bacteria), which can be fatal.
• Cattle ticks transmit Texas cattle fever (protozoan).

Arthropod Circulatory System

• Arthropods have an open circulatory system where blood (haemolymph) bathes internal organs directly.
• The body cavity is a haemocoel (blood chamber).
• One or more hearts pump haemolymph into sinuses.
• Contraction of the heart pumps blood out vessels into sinuses, and relaxation draws blood in through ostia (pores).

Arthropod Respiratory System

• Terrestrial arthropods use an efficient tracheal system of air tubes for direct oxygen transport to tissues and allow high metabolic rates, but may limit body size.
• Aquatic arthropods respire with various forms of internal or external gills.

Arthropod Excretory System

• Paired excretory glands called coxal, antennal, or maxillary glands are present in some arthropods.
• Others have excretory organs called Malpighian tubules.
• The nervous system is similar to that of annelids, with a dorsal brain connected by a ring around the gullet to a double nerve chain of ventral ganglion; fusion of ganglion in some species.
• Arthropods have well-developed sensory organs, and behavioral patterns are much more complex than those of most invertebrates, with a wider occurrence of social organization (bees, ants).

Arthropoda Characteristics

• Eyes vary from simple light sensitive ocelli to a compound mosaic eye.
• Other sensory structures are well defined for touch, smell, hearing, balancing, and chemical reception.
• Sexes are usually separate, with paired reproductive organs and duct; usually internal fertilization; oviparous, ovoviviparous, or viviparous; often with metamorphosis and parthenogenesis in some taxa.

Arthropoda Metamorphosis and Resource Use

• Many arthropods undergo metamorphic changes that have different larval and adult stages.
• Larvae and adults feed on different organisms and occupy different habitats to avoid intraspecific competition.

Arthropoda Classification

• Arthropods are ecdysozoan protostomes in the clade Panarthropoda.
• Groupings among subphyla are now based on molecular data, which conflicts with traditional classifications.
• Molecular evidence divides the group Uniramia (single branching appendages) where insects are now in subphylum Hexapoda and the others are under the subphylum Myriapoda.

Arthropoda Classification: Mandibulate Hypothesis

• Phylogenetic relationships are highly controversial.
• The "Mandibulate hypothesis" states that myriapods, hexapods, and crustaceans are more closely related due to a shared mouthpart, the mandible, forming the clade Mandibulata.
• Other arthropods with no mandibles form Chelicerates.
• This is supported by molecular evidence.

Chelicerates and Myriapods: Subphylum Myriapoda

• Myriapods mean “many footed” and describes the members of this group.
• They have mandibles rather than chelicera for feeding.
• Generally have two tagmata (head and trunk) with paired appendages along most segments.
• It includes Chilopoda (centipedes), Diplopoda (millipedes), Pauropoda (pauropods), and Symphyla (symphylans).
• Myriapods use trachea to transport gases.
• Excretion is usually by Malpighian tubules which evolved independently from Chelicerata.

Class Chilopoda: Centipedes

• Centipedes have flattened bodies found in moist areas under logs, bark, and stones.
• They are agile carnivores that eat earthworms, cockroaches, and other insects.
• They kill prey with venom claws and then chew with mandibles.
• Approximately 3,000 species exist worldwide; most are harmless to humans, but are a few large, tropical centipedes are dangerous.
• Centipede bodies have up to 177 segments.
• Most body segments bear a single pair of jointed legs.
• Appendages of the first body segment form poison claws.
• Some lay eggs, and others are viviparous with young that resemble adults and do not undergo metamorphosis.

Class Diplopoda: Millipedes

• More than 10,000 species of millipedes exist worldwide.
• They have cylindrical bodies with 25 to more than 100 segments reinforced with a calcium carbonate exoskeleton.
• The short thorax consists of 4 segments, each bearing one pair of legs while abdominal segments bear two pairs of legs.
• The head has 2 clumps of simple eyes, a pair each of antennae, mandibles, and maxillae.
• Millipedes are Herbivores, slower than centipedes

Arachnids: Ticks and Mites

• The most medically and economically important arachnids.
• About 30,000 species have been described (maybe up to 500 000 to 1 million species).
• They are both aquatic and terrestrial, and inhabit deserts, polar areas, and hot springs.
• Most mites are less than 1 millimeter long while ticks may range up to 3 cm due to distension from feeding.
• Unlike other arachnids, they complete fusion of the cephalothorax and abdomen and no sign of external segmentation.
• Adult mites and ticks possess 4 pairs of legs.

Important Mites

• House dust mites are free-living and often cause allergies.
• Spider mites are important agricultural pest mites that suck out plant nutrients.
• Chiggers (larval Trombicula mites) feed on dermal tissues and cause skin irritation.
• Hair follicle mite Demodex is harmless, but other species cause mange in domestic animals.
• Human itch mites burrow into skin and cause intense itching (scabies).

Vectors for Disease

• Tick species of Ixodes carry Lyme disease (bacteria) and is Debilitating if untreated causing Impairment of motor & sensory function.
• Tick species of Dermacentor transmit Rocky Mountain spotted fever (bacteria), which can be fatal.
• Cattle ticks transmit Texas cattle fever (protozoan).

Chelicerata vs Mandibulata Summary

• The Mandibulate hypothesis indicates Independent evolution.
• Chelicerates are spiders, scorpions and ticks with -.
• Myriapoda are Millipedes Centipedes
• Chelicerata vs Mandibulata:
• -/+ mandibules (mouth parts)
• Malpighian tubules (excretion) & Tracheal system (respiration)
• Spiders, scorpions and ticks have a Cephalothorax, abdomen & 2º loss of antennae.
• Spiders produce Silk.
• Ticks and Mites have a greater medical impact than spiders
• Mandibulates have antennae
• Millipedes are slow herbivore with a head, trunk, abdomen and 2 pairs of legs
• Centipedes are fast carnivores with a head and trunk and 1 pair of legs per segment

Crustaceans

• Crustacea are called the "Insects of the sea"
• They are mainly found in marine, but many freshwater and a few terrestrial spp
• They have Over 67,000 living species.
• Composition: insects and crustacea compose over 80% of all named animal species
• The most abundant animals in the world are members of the copepod genus Calanus.

Crustacean Characteristics

• Cuticles composed of chitin, protein, and calcareous material/
• Three tagmata: head, thorax, and abdomen. In most, one or more thoracic segments are fused with the head as a cephalothorax.
• Head with a pair of mandibles and two pairs of maxillae and two pairs of antennae.
• One pair of appendages on each of the addition segments although some segments may lack appendages.
• All appendages, except first antennae, are ancestrally biramous.
• The anterior end is a non-segmented rostrum.
• The Telson, with the last abdominal segment and uropods, forms a tail.
• The Dorsal covering is the carapace.

Crustacean Appendages

• There is a Biramous plan (2 branches).
• Basal portion: protopod (basis and coxa).
• Lateral branch: exopod.
• Medial branch: endopod.
• Exite (Gill): epipod.
• Walking legs become secondarily Uniramous.

Crustacean Appendages & Differences

• Malacostraca (and Remipedia) have paired appendages on the abdomen (swimmerets), while other classes typically do not.
• Crustaceans generally have an open or lacunar circulatory system, which has no veins to separate the blood from interstitial fluid.
• Hemolymph exits the heart through arteries then passes to the hemocoel to return to the heart via sinuses or spaces but no veins.
• A dorsal heart is a single-chambered sac of striated muscle that is the chief propulsive organ for the hemolymph from the pericardial sinus.
• Valves in the arteries prevent backflow of hemolymph to the sinuses.
• Small arteries empty into tissue sinuses, which in turn discharge into a large sternal sinus.
• Hemolymph is pumped to the gills from the afferent (sternal) sinus for oxygen and carbon dioxide exchange and returned to the heart.

Crustacean Excretory System

• Antennal or maxillary glands (green glands) occur in decapods.
• The End sac of the antennal gland has a small vesicle and a spongy labyrinth.
• The Labyrinth connects by an excretory tubule to a dorsal bladder that opens to an exterior pore.
• Hydrostatic pressure within a hemocoel provides a force for filtration of fluid into the end sac.
• Resorption of salts and amino acids occurs as the filtrate passes the excretory tubule and bladder.
• The Excretory System mainly regulates the ionic and osmotic composition of the body fluids.
• Freshwater species excrete excess water while marine species excrete excess salt.
• Nitrogenous wastes are excreted across thin areas of cuticle in the gills.

Crustacean Nervous & Sensory Systems

• There are more fused ganglia than in other arthropods
• A double ventral nerve cord has a pair of ganglia for each segment to control appendages.
• The largest sensory organs are Eyes and statocysts.
• Tactile hairs occur on the body, especially on chelae, mouthparts, and telson.
• Chemical sensing of taste and smell occurs in hairs on antennae and mouth.
• Compound eyes, made of many units called ommatidia.

Crustacean Reproduction

• Most are dioecious with various specializations for copulations.
• Barnacles are monoecious but generally cross-fertilize.
• In some ostracods, males are scarce, and reproduction is by parthenogenesis.
• Most crustaceans brood eggs in brood chambers, in brood sacs attached to the abdomen, or attached to abdominal appendages.
• The Nauplius larva is unlike the adult in form and undergoes metamorphosis.
• Crayfishes develop directly without a larval form.

Crustacean Ecdysis (Molting)

• It is Necessary for a crustacean to increase in size.
• EXOSKELETON DOES NOT GROW.
• Molting animals grow in the intermolt phases (instars).
• When the body fills the cuticle, the animal is in the premolt phase.
• Epidermal cells enlarge before ecdysis, and secrete a new epicuticle & then begin secreting a new exocuticle.
• The soft new cuticle stretches and then hardens with the deposition of inorganic salts (Ca2+).
• Molting occurs often in young animals and may cease in adults.

Hormonal Control of Ecdysis

• Molting occurs often in young animals as they grow and may slow down in adults.
• Environmental factors like temperature, day length, or other stimuli trigger the central nervous system to begin ecdysis.
• The central nervous system decreases the production of molt-inhibiting hormone by the X-organ which is a group of neurosecretory cells in the brain or eye-stalk of most decapods.
• This promotes the release of molting hormone from the Y-organs that lie beneath the epidermis of the adductor muscles around the mandibles which produce ecdysone that leads to ecdysis.
• Ecdysone is only needed to initiate ecdysis, which proceeds on its own.

Crustacean Feeding Habits

• The Same fundamental mouthparts are adapted to a wide array of feeding habits and food sources.
• Mandibles and maxillae are for ingestion, and maxillipeds hold and crush food.
• Walking legs like chelipeds are used to capture food.
• Suspension feeders generate water currents in order to feed on plankton, detritus, and bacteria, and use setae on their legs to strain food from the water.
• Predators consume larvae, worms, crustaceans, snails, and fishes and have interesting adaptations for killing prey.
• Scavengers eat dead animal and plant matter.

FYI: Crustacean in Tuna Can

• Found living in a can of tuna.
• Initial thought to be Cymothoa exigua tongue-eating louse, however, lab results indicate Megalopa, a type of tiny crab.

Order Amphipoda

• Resemble isopods that also lack a carapace, have sessile compound eyes, and one pair of maxillipeds
• However, their bodies are compressed laterally, and gills are in the thoracic region.
• Abdominal and thoracic limbs are grouped for jumping and swimming.
• Many are marine, others are beach-dwelling, some are freshwater, and a few parasitic forms.
• Development is direct without true metamorphosis.

Order Euphausiacea (krill)

• About 90 species with many species being important ocean plankton called krill.
• Small crustaceans from 3 to 6 cm long and have a carapace fused with all thoracic segments but does not completely enclose gills.
• Lack maxillipeds and all limbs have exopods.
• Most are bioluminescent with a light-producing organ called a photophore.
• Eggs hatch as nauplii, and development is indirect and metamorphic.
• Forms a major component of the diet of baleen whales and of many oceanic fishes.
• Baleen whales sieve the water for these tiny animals.

Order Decapoda

• Approximately 18,000 species, including crayfishes, lobsters, crabs, and true shrimp, have important ecological and economic value (important culinary items).
• Crabs have a broader cephalothorax and reduced abdomen as compared to crayfish or lobsters.

Crustacean Adaptive Diversification

• Crustaceans are unquestionably the dominant arthropod in marine environments and exploit virtually all aquatic resources.
• Crustaceans also share dominance in freshwater environments with the insects, but invasion to terrestrial areas is limited.
• Malacostraca is the most diverse, with members of Copepods and Ostracods being the most abundant.
• Both groups have planktonic suspension feeders and numerous scavengers.
• Herbivorous copepods form the base of nearly all marine food webs and play an important role in oceanic ecology.
• Copepods are particularly successful as parasites of both vertebrates and invertebrates.

Crustacean Summary

• Mandibulate, two pairs of antennae, biramous appendages, and serial homology.
• They have Feather like gills with thin cuticle for respiration, open circulatory system, and Green gland excretory system (osmoregulation).
• Ecdysis (molting)
• Nauplius larva - metamorphosis or direct development
• Classes: Ostracoda (mussel shrimp), Copepoda, Thecostraca (barnacles), Malacostraca (largest and most diverse) with: Isopoda (terrestrial; dorsoventral flattened) & Amphipoda (laterally flattened) Both lack a carapace. Euphausiacea (krill), Decapoda (crabs, shrimp) both Have a carapace.

Hexapoda: Subphylum Hexapoda

• Hexapoda are named for the presence of six legs, which are all uniramous.
• They have three body segments (tagmata)- head, thorax, and abdomen.
• Appendages attach to the head and thorax while abdominal appendages may be greatly reduced or totally absent.
• Two classes are within Hexapoda: Entognatha and Insecta.
• Small group with the bases of mouthparts enclosed within the head capsule, Entognatha.
• Enormous class that have ectognathous mouthparts, but the bases of the mouthparts lie outside the head capsule, Insecta.

Hexapoda: Class Entognatha

• Entognathous mouthparts are enclosed within the head capsule.
• Orders Protura & Diplura are tiny, eyeless, that inhabit soil or dark, damp places.
• Order Collembola (Springtails) leap 20x body length and inhabit soil, decaying pant matter, or freshwater pond surfaces, and along the sea shore.

Hexapoda: Class Insecta

• The most diverse and abundant of all arthropods with 1.1 million classified species, but 30 millions estimated.
• Range from less than 1 mm to 20 cm in length, and the larger insects are tropical.
• Entomology is the study of insects.
• There are numerous variations in body form where Land beetles are thick and shielded while aquatic beetles are streamlined.
• Walking sticks are long and slender on branches while cockroaches are flat so as to live in crevices
• Butterflies have the broadest wings of all.

How Do Insects Differ From Other Arthropods?

• Ectognathous mouthparts are outside the head capsule.
• Usually two pairs of wings, in the thoracic region.
• The Exoskeleton is composed of complex plates, or sclerites, connected by flexible hinge joints with muscles attaching to the sclerites that allow for precise movement.
• Rigidity of the exoskeleton is due to scleroproteins and not chitin matter (chitin is still an important component of cuticle).
• Insects Waterproofness and lighter weight allows for flight as compared to crustaceans.

Insecta: External Form & Function

• The Cuticle of body segments is composed of four plates: a dorsal tergum, a ventral sternum, and a pair of lateral pleura.
• The Pleura of abdominal segments are partially membranous rather than sclerotized.
• The head is usually equipped with a pair of large compound eyes; one pair of antennae and three ocelli.
• Antennae varies greatly in function for either touch, taste, or hearing.
• Mouthparts are formed from hardened cuticle and consist of labrum, a pair of mandibles, and maxillae, labium, and hypopharynx.

Gas Exchange

• The Chief gas exchange organ of holothuroids.
• It is a Branching diverticulum of the cloaca (or rectum).
• Radiating cloacal muscles contract for cloacal dilation when water enters through anus.
• The anal sphincter closes, the cloaca contracts, and several short inhalations to fill occurs.
• Once fill a long exhalation (contraction of the tree) to empty occurs.
• Sea Cucumbers may Eviscerate

Classification: Phylum Echinodermata

(Subphylum Eleutherozoa)

• Class Asteroidea, have a Madreporite that is aboral, possess Pentaradiate Symmetry, and they have Suckers;podial ambulacral.
• Class Ophiuroidea, have a Madreporite that is oral, possess Pentaradiate Symmetry, lack Suckers & Pedicellarie.
• Class Echinoidea, have a Madreporite that is aboral, possess Pentaradiate Symmetry, and they have Suckers;podial ambulacral.
• Class Holothuroidea, have a Madreporite that is internal, possess Pentaradiate Symmetry, lack Suckers & Pedicellarie.
• Asteroidea have open ambulacral Groove and Pedicellarie is present while Ophiuroidea, Echinoidea & Holothuroidea have closed ambulacral Groove and Pedicellarie is .

Class Crinoidea (sea lilies): Subphylum Pelmatozoa

• 625 species.
• The Body disc or calyx is covered with a leathery skin or tegument of calcareous plates.
• The 5 arms branch to form more arms, each with lateral pinnules as in a feather.
• Calyx and arms form a crown.
• Sessile forms have a stalk formed of plates appears to be jointed and may bear cirri.
• Crinoids lack a madreporite, spines, and pedicellariae, posses Open ambulacral grooves (like asteroidea)

Phylum Hemichordata

• A Link between echinoderms and chordates.
• Marine animals were formerly considered a subphylum of chordates, based on the possession of gill slits, and a rudimentary notochord.
• Hemichordates share characteristics with both echinoderms and chordates.
• A Hemichordate notochord is really a buccal diverticulum (called a stomochord) and NOT homologous to a chordate notochord

Phylum Hemichordata: Characteristics

• Body divided into proboscis, collar, and trunk; buccal diverticulum in the posterior part of the proboscis.
• Are Bilaterally symmetrical, soft bodied, triploblastic, and free living.
• The Digestive system is complete with Longitudinal and Circular muscle.
• A Single glomerulus connected to blood vessels may have excretory function (metanephridium).
• Respiratory system of gill slits connecting the pharynx with outside exists
• A Circulatory system of dorsal and ventral vessels and a dorsal heart.
• They have a larval form called Tornaria larvae and Sexes are separate with external Fertilization in some species.
• Some species contain a ciliated tornaria larva develops similar to that of echinoderm larva and undergo asexual reproduction.

Class Enteropneusta

• Wormlike acorn worms with a mucus-covered body.
• Have 3 distinct regions of body: Proboscis, short collar, and trunk.
• The proboscis probes surroundings, and food collected on surface mucus.
• Cilia carry particles to the mouth where contraction of body musculature and forces excess water out through gill slits.

Class Pterobranchia

• Small animal, usually 1 to 7 mm in length with a Basic plan similar to that of Enteropneusta.
• Many individuals may live together in collagenous tubes whereas Zooids are not connected.
• The Body is divided into three regions with Proboscis, collar, and trunk.
• Ciliated grooves on tentacles and arms collect food
• Both dioecious and monoecious species exsist with asexual reproduction by budding.

Deuterostome Summary

• Echinodermata & Hemichordata Deuterostomes with Echinoderm adults that possess pentaradial symmetry but Bilateral symmetry as larvae.
• Deuterostomes have a Blastopore that becomes the anus and enterocoelous coelom formation with radial cleavage.
• Echinodermata contain a Water vascular system.
• Hemichordata are Marine worms that Link to chordates through Gill slits and link to echinoderms through Tornarian larvae.

Vertebrata: Subphylum Vertebrata

• Early vertebrates were substantially larger and more active than protochordates because of the musculoskeletal, physiological and sensory system modifications.
• The Living endoskeleton acts as a framework for the body and internal supportive structure.
• The Endoskeleton was probably composed initially of cartilage and later of bone & the Segmented body muscles (myomeres) are altered from the V-shaped cephalochordate form to a W-shaped vertebrate form also Fin rays of dermal origin in fins, aided in swimming.
• Digestive, respiratory, circulatory, and excretory systems modified to support increased metabolic demands of large size and active food-seeking lifestyle.
• Pharynx modified into a muscular pump passing water across internal gills. + a chambered heart to pump blood around body: Ventral 3-chambered heart & erythrocytes containing hemoglobin
• Efficiency for excretion of wastes is achieved through a muscular gut with accessory digestive glands and paired, glomerular kidneys.

Subphylum Vertebrata: Sensory System Modifications

• Active predatory lifestyles require new sensory, motor, and integrative control mechanisms for locating and capturing food.
• The Anterior end of nerve cord enlarged as a tripartite brain (forebrain, midbrain, and hindbrain).
• Sensory organs designed for distance reception evolved giving rise to; Sophisticated Eyes & Pressure receptors with inner ears (equilibrium/sound). Chemical Receptors: Olfactory organs & Lateral-line Receptors used to pick up vibrations in water Electrical Receptors: Ampullary organs

Subphylum Vertebrata: Neural Crest

• Development of the vertebrate head and special sense organs was largely the result of two embryonic innovations present ONLY IN VERTEBRATES: the NEURAL CREST and ECTODERMAL PLACODES.
• In early development, as the nerve cord is forming, neural crest cells leave the nerve cord and move through the body to form important nerves, neural ganglia, and many head and facial features.

Subphylum Vertebrata: Ectodermal Placodes

• Plate-like ectodermal thickenings that appear on either side of the neural tube.
• Ectodermal Placodes are anatomically distinct from neural crest cells, are found only in vertebrates & form sensory organs or receptors.

Subphylum Vertebrata: Hox Genes

• Vertebrates differ from all other animals in having four clusters of Hox genes, which have arisen by two genome duplication events.
• Hox genes may play a key role in the evolutionary diversity that characterizes the vertebrates with and gene duplication may be the primary mechanism for the evolution of complexity in higher organisms.
• Hox genes are a Group of related genes that control the body plan of the embryo along the anterior-posterior (head-tail) axis.

Subphylum Vertebrata Summary

• Chordate hallmarks: (tattoo onto your forehead) with diagnostic features of chordates and endoskeleton

1. Notochord (a skeletal rod) present at some stage in the life cycle.
2. Single, dorsal, tubular nerve cord; anterior end of cord usually enlarged to form brain.
3. Pharyngeal pouches present at some stage in the life cycle; in aquatic chordates these develop into pharyngeal slits.
4. Endostyle /thyroid gland derived from the endostyle.
5. Postanal tail may or may not persist.
6. endoskeleton consisting of vertebral column and a cranium.
7. Complex, muscularized digestive tract with distinct liver and pancreas.
8. Closed circulatory system with multichambered ventral heart.
9. Excretory system consisting of paired, glomerular kidneys
10. Tripartite brain
11. NEURAL CREST and ECTODERMAL PLACODES: Two vertebrate embryonic innovations resulted in vertebrate head and special sense organs, respectively.

Vertebrata: Characteristics

• The Chief diagnostic features of chordates - notochord, dorsal tubular nerve cord, pharyngeal pouches, endostyle or throid gland and post anal tail all present at some stage of the life cycle.
• The Integument of two divisions, an outer epidermis of stratified epithelium and an inner dermis of connective tissue; many modifications of skin: glands, scales, feathers, claws, horns and hair.
• Distinctive cartilage or one endoskeleton consisting of vertebral column and a head skeleton (cranium and pharyngeal skeleton) is derived largely from neural crest cells.
• Complex, W-shaped muscle segments or myomeres to provide movement occurs when pharyngeal pouches open to the outside as slits and bear gills.
• The Circulatory system consists of a ventral heart of multiple chambers, and closed blood vessel system of arteries, veins, and capillaries.

Gnathostomata

• Three pairs of semicircular canals of the inner ear and a notochord that is partly or completely replaced by centra of the vertebrae

Caudal Fins

• The Vertebral column extends into the upper lobe and provides lift to the posterior region of the body for functional stiffness.
• The Vertebral column ends with the modified vertebrae structure (internally asymmetrical) and has greater versatility for fine movement.
• The Vertebral column extends to tip without upturning.

Teleosts

• Most fish use gas bladders to achieve neutral buoyancy.
• Gas Bladder controls volume:weight ratio for both positive and negative buoyancy.
• If the Volume of s.b. decreases and the Water pressure increases then the Density of fish increases.
• Swim bladder adjusts the density of fish to equal that of the surrounding water
• The gas volume Must be adjusted at different depths

Gills

• Aquatic gas exchange organs that promote Counter-current exchange.
• Gills maintain Stable gas (O2, CO2) diffusion gradients.

Teleost Osmoregulation in Seawater

• Solves the problems of Water being lost to the environment and the secretion of excess NaCl by drinking seawater.

Teleost Osmoregulation in Freshwater

• Solves the problems of Water being gained from the environment and the replacement of the salts lost to the environment when the Fish does NOT Drink.

Migration in Teleosts (Euryhaline)

• Anadromous species migrate from a freshwater habitat as adults to a seawater habitat as larvae-juveniles(Salmon).
• Catadromous species migrate from a seawater habitat as adults to a freshwater habitat as larvae-juveniles (Freshwater Eels).

Reproduction & Growth

• Most fishes are dioecious with external fertilization and external development.
• Sequential and synchronous hermaphrodites exist.
• Guppies and mollies are ovoviviparous fish that develop in the ovarian cavity retaining eggs until hatch.
• Some sharks are viviparous with some kind of placental attachment to nourish young.
• Most oviparous pelagic fish lay huge numbers of eggs.

Summary of Fishes

• Have gills, fins, and dermal scales
• Agnathans