Nov 15 - Animals Lecture #17 - Fishes I

Separate internal gill openings cranium poorly

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Separate internal gill openings Cranium poorly developed and vertebrate absent o Doesn’t surround the brain o Some say not even a vertebrate but if basal plate is there prof thinks it is a vertebrate Mouth with ‘ tounge ‘ (muscular structure – not conventional tongue) and four rows of keratinized teeth Feed on soft-bodied invertebrates and dead or dying large organisms Very flexible and can tie itself into a knot to tear off pieces of flesh o Knotting – multifunctional used for predator and avoidance o Tie itself to push out from predators Slime function include: o Aid in burrowing – small amounts of slimes giving burrow structural integrity o Cover scavenged meal – if it smells rotten fish, It will cover the scavenged meal in slime so it will diminish the scent from leaking out reducing the # of other scavengers looking o Defense against predation – slime would clog the gills of larger fish and it would cough it out o Osmoregulation? Read below Hagfish generally considered to be isosmotic to surroundings
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o Sea water [Na+] = ~ 450 mmol/L o Hagfish plasma [Na+] = 549 mmol/L o Slime contains high levels of Ca 2+, Mg 2+ and K+ and low Na+ o No evidence of active Na+ transport across gut, gills or skin Myxinid Reproduction o Females outnumbers by 100:1 o Male and females gonads present in some o No specialized reproductive ducts o Mating never been observed o Fertilized eggs had not been found since 19 th
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  • Fall '08
  • subphylum Vertebrata, gill openings, Wshaped vertebrate form, Largest vertebrate group

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