notes-1-25 - Subphylum:Craniata Nojaws...

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1/25/10 Subphylum: Craniata No jaws Agnathans – informal grouping Cyclostomes- Lamprey + hagfish Roundmouth- no jaws Lampres- 10 species Go upstream to breed Shed gametes, die Larva-ammocetes Thought to be different species very different than adults Stays as larvae for years Metamorphoses- migrates to ocean or lake (brook lamprey stay in stream) Feeding- mostly parasitic Horny teeth (keratin) = rasp off flesh Create suction by pulling tongue back Respiration – water- when feeding, waterin +out though gill openings (gill  pouches lined with gill filaments) Endoskeleton- Cartillage, but no bone (loss may be secondary) Notochord Arcualia- Segmental (cartilage) Lie laterally to nerd cord and notochord Homologous to vertebrate-probably\ Economic Impact in great lakes- huge welland canal- 1929 By 1946, lampreys in L. Superior destroyed fisheries Ammoceotes- Greater cephalization than amphioxus 3 part brain Sense organs- ligh receptors, otic cesicles, olfactory sac Muscles and gills associated w/ pharynx (pump h20 through pharynx) Heart- pumps blood But 2 are very alike… Di an animal like amphioxus give rise to craniates through ammocoetes-like ancestors?
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Hagfish- Myxini Marine Jawless agnathans Bottom-feeding scavengers Small,soft invertebrates Dead fish Short, tentacle-like papillae around mouth Two rasping plates Single nostril- water for resporation Flows in nostril to pharynx Out pharyngeal slits Eyes- vestigial, covered w/ skin Able to produce great amounts of slime (mixini=nasal slime) No trace of bone, no arcualia Probably sister group of lamprets Probably more closely related than though 2/3 years ago (molecular + neural crest cell  evidence) Both are Agnatha- no jaws Ostracoderms- extince- small 2-3 cm Artificial grouping- no taxonomic staus Several different ancestors Polphyletic group- does not contain the most recent common ancestor One group- close to lampreys All ostracoderms lack jaws – agnatha Bony plates- larger at anterior
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notes-1-25 - Subphylum:Craniata Nojaws...

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