notes-1-25 - 1/25/10 Subphylum:Craniata Nojaws...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
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?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
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
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

notes-1-25 - 1/25/10 Subphylum:Craniata Nojaws...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online