Fish Biology PDF

Fish Introduction to Fishes 1.​ Aquatic vertebrate with gills and limbs in the shape of fins a.​ 48% live in marine environments b.​ 41% live in freshwater environments c.​ 1% are diadromous (move between salt and fresh water during a cycle) Diadromy...

Fish Introduction to Fishes 1.​ Aquatic vertebrate with gills and limbs in the shape of fins a.​ 48% live in marine environments b.​ 41% live in freshwater environments c.​ 1% are diadromous (move between salt and fresh water during a cycle) Diadromy 1)​ Anadromous a)​ Spends most lives in the ocean but returns to freshwater to reproduce. 2)​ Catadromous a)​ Live in freshwater and reproduce in the ocean Early Vertebrates -​ Arose in the Ordovician period of the Paleozoic era -​ Ostracoderms= “shell-skinned” -​ Bony head shield, developed eyes, lacked true jaws -​ Superclass Gnathostomta -​ Known from the Silurian period true jaws -​ Jaws create a diversity of foods and are a form of defense ​ Early Gnathostomes ○​ Placoderemi- “Plate-skinned” ○​ Acanthodii- “Spiny sharks” ​ Lateral line, ossified operculum  -​ Class Osteichthyes, Modern Bony Fishes -​ Subclass Sarcopterygii- Lobe-finned bony fishes ​ ​ Three Major Lineages: -​ Actinstia (coelacanths) ​ Devonian period, thought to be extinct until 1938 ​ First species described was Latimeria chalumnae -​ Dipnoi (lungfish) ​ Devonian period ​ >100 species described ​ 6 extant species ○​ Ability to breathe air -​ Tetrapoda (tetrapods) ​ Predatory fishes up to 4 m ​ Occurred in shallow, freshwater environments. -​ Subclass Actinopterygii- Ray-finned bony fishes -​ Chondrostei (paddlefish/sturgeon) ​ Silurian Period ​ Cartilaginous fishes ○​ Heterocercal tail, placoid scales, lacks gas bladder -​ Neoptrygii (all other bonyfishes) ​ Division teleostei (teleosts) ○​ Homocercal tail, gas bladder, cycloid/ctenoid scales”. Respiration a.​ Gill structure i.​ Gill Arches- Provide support ii.​ Gill rakers- function in feeding iii.​ Gill filaments- where gas exchange occurs  b.​ Countercurrent Exchange ​ Water and blood flow in opposite directions ○​ Results in an O2 gradient ○​ Water passes through the gill arch c.​ Gill Ventilation ​ Generate flow of water across the gils ○​ Gill pumping- synchronized pressure changes in the buccal and operculum chambers (most bony fishes) ○​ Ram Ventilation ​ keeping the mouth open while swimming (sharks, tunas) ○​ Aerial Respiration ​ Facultative air breathers (supplement gill respiration with oxygen) (Gars/bowfin) ​ Obligate air breathers- must have access to atmospheric oxygen (South American lungfish) ​ Breaths through lungs, gas bladders, skin Gas Bladder (Buoyancy Regulation) ​ Flexible-walled, gas-filled chamber in the body cavity ​ Forms from the esophagus ○​ The pneumatic duct connects the gut with the gas bladder ​ Physostomous- pneumatic duct is retained ​ Physoclistous- pneumatic duct not retained ​ Allows fish to maintain position in the water column. ​ Rete mirable is the wonderful net network of veins and arteries flowing in opposite directions (counter current exchange) Sound Reception in Gas Bladders ​ Uses Otoliths (earstones) in the middle ear ​ Gas Bladder functions like an eardrum ○​ Weberian ossicles- series of bones that connect the gas bladder to the ear Locomotion ​ Most efficient shape for moving through water is a width about 25%-35% of the length ○​ Myomeres are muscles on the side of the fish used for forward propulsion ​ Specialized Locomotion ○​ Walking ○​ Flying Feeding ​ Mandibular versus pharyngeal teeth ​ Jaws open and move forward. ○​ Creates rapid flow of water into the mouth= suction feeding ​ Gill Rakers ○​ Projections on the gill arches used in feeding ​ Large prey, fewer short rakers (15-30) ​ Small prey= more, longer gill rakers (>100) Reproduction and Development 1.​ Larval stage a.​ First stage after hatching that does not resemble the juvenile or adult form i.​ Fertilized egg > larvae > juvenile > adult 2.​ Indeterminate growth a.​ Grow throughout life i.​ Risks increased reproductive success, greater predator avoidance, and additional feeding opportunities. 3.​ Reproduction a.​ Most fish exhibit external fertilization i.​ Spawns, releases eggs into the water b.​ Internal fertilization i.​ Occurs with Elasmobranchs, poeciliids ii.​ Modified structures as intermittent organ 1.​ Elasmos have claspers. Modified pelvic fins 2.​ Poecilids have a gonopodium. Modified anal fin 4.​ Development a.​ Oviparous- eggs laid outside the body, embryo gets nourishment from egg yolk b.​ Viviparous- Young develop inside the mother and receive nourishment from the mother c.​ Ovoviviparous- eggs are produced but they are retained inside the mother until hatching, nourishment comes from egg yolk 1.​ Larval Stage a.​ Begins when young switch from yolk to an external food source 2.​ Juvenile stage a.​ Begins when body system development is complete i.​ Resembles adults b.​ Some deviate i.​ Smoltification of anadromous salmonids 1.​ Also the American eel 3.​ Adult a.​ Characterized by attainment of sexual maturity Sensory Systems ​ Hearing ○​ Otoliths, Gas Bladder ​ Detects predators and prey. ​ Used for communication ○​ Lateral line ​ Consists of neuromast cells that detect vibrations and changes in water pressure ​ Used for spatial orientation, school behavior predation ​ Vision ○​ Light refraction: bending of light when it enters a medium where its speed is different ○​ Photoreceptor cells ​ Rods: Light reception ​ Cones color reception ○​ Tapetum lucidum ​ Layer of guanine crystals behind the receptor cells of the retina that reflects light back ​ Aids in low-light vision ​ Smell ○​ Olfactory receptors- receive chemical cues from the environment ​ Locates food, mates, and how to return to natal areas ○​ Electro reception- detects electrical fields ​ Electrical organ discharge, ability to produce an electrical current ○​ Magnetic reception- ability to detect the earth’s