Phylum Chordata and Subphylum Vertebrata

1. Phylum Chordata and Subphylum Vertebrata Fred Searcy Zoology

2. Phylum Chordata • Big Four Chordate Traits • Presence of a notochord • Presence of pharynx with pouches or slits in their walls • Dorsal, hollow nerve cord, and • Post anal tail

3. Notochord(Gr. Noton = back, L. chorda = chord) • Flexible, endoskeletal rod of turgid, living cells • Typically ventral to central nervous system and dorsal to digestive system • Designed for support (internal skeleton) • Often become obliterated in vertebrates

4. Pharynx with Pouches or Gill Slits • Area in the mouth region which arises from endoderm • Forms pouches in embryo • May rupture to form external openings called gill slits • May remain throughout life or close up • Opening begins as ectodermal groove which meets endodermal out pocketing

5. Gill Pouches & Gill Slits • Aquatic animals • Respiratory structures • Other animals • Other structures • Eustachian tube • Middle ear cavity • Palatine tonsils (mammals) • Thymus gland • Parathyroid glands • # varies animal to animal

6. Dorsal, Hollow, Central Nervous System • Brain & spinal chord both contain a central cavity • Arises from longitudinal neural plate in dorsal ectoderm (folds over to form tube) • Nerves branch off • 10 cranial in fish/amphibians • 12 in reptiles/birds/mammals

7. Post anal Tail • Allows for greater motility and free-swimming existence • Later enhanced by fishes to from fins

8. Biological Contributions of Chordates • Endoskeleton which evolved from notochord • Continuous growth without molting • Allows for greater size • Muscle attachment more efficient, greater mobility • Perforated pharynx • Allowed development of internal gills & jaws • Predatory habit • Led to highly differentiated brain & paired sense organs • Paired appendages • Developed into joined limbs for locomotion or flight • Neoteny • Sexual maturity in larval body form

9. Subphylum Vertebrata • Vertebrae • Independent axial skeleton • Provides more rigidity than notochord • Provides more flexibility • Formed from cartilage, bone or both

10. Vertebrate Characteristics • Chordate characteristics at some stage in life cycle • Integument of 2 divisions (epidermis from ectoderm and endodermis from mesoderm) • Notochord typically replaced by vertebrae • Muscles attached to skeleton for movement • Complete digestive system ventral to spinal column • Ventral heart with 2-4 chambers, closed circulation

11. Vertebrate Characteristics, continued • Large, organ-filled coelom • Paired meso- or metanephric kidneys with ducts to outside • Brain typically with 5 vesicles • 10-12 pairs of cranial nerves, autonomic system • Endocrine system of ductless glands • Sexes usually separate, paired gonads which empty via ducts to cloaca or special opening near anus • Body composed of head, trunk, tail – neck in some, typically with 2 pairs of appendages.

12. Classification of Chordates • Subphylum Urochordata – sea squirts, tunicates • Subphylum Cephalochordata – lancets (amphioxus) • Subphylum Vertebrata • Superclass Agnatha – jawless fish • Class Myxini – hagfishes • Class Cephalaspidormorphi – lamprey eels • Superclass Gnathosotmata – with jaws • Class Chondrichthyes – sharks, skates, rays • Class Osteichthyes – bony fish • Class Amphibia – frogs, salamanders • Class Reptilia – snakes, lizards • Class Aves – birds • Class Mammalia – mammals

13. Subphylum UrochordataSubphylum Cephalochordata

14. Phylum Urochordata • Invertebrates (2,000 species) • Exclusively marine from shoreline to great depths • Common name tunicate (sea squirt) from outer covering of cellulose • Adult doesn’t have all 4 chordate traits but larva does (retrograde evolution)

15. Class Ascidiacea • Ascidians commonly called Sea Squirts • Mostly sessile • Solitary, colonial, compound • Excurrent and incurrent siphons • Endostyle with mucous traps food • Ventral heart pumps blood both directions • Vanadium and niobium found in blood • Hermaphroditic, single ovary & testis • External fertilization

16. Subphylum Urochordata • Class Ascidiacea • Chordate Traits • Adult has only pharyngeal gill slits • Larva has all four • Does not feed

17. Subphylum Cephalochordata • Marine • Laterally compressed • Translucent • Sand bottoms of coastal waters • Usually less than 7cm • Common name Lancet • Previously Amphioxus now Branchiostoma • 25 species worldwide, 4 in US

18. Subphylum Cephalochordata • Exhibit all 4 chordate traits • Atrium & atriopore • Wheel organ • Separate sexes

19. Vertebrates • Most successful of all animals • Characteristics • Big four chordate traits at some stage in life cycle • Integument of two divisions: epidermis (ectodermal) and dermis (endodermal) • Modifications include • Glands • Scales • Feathers • Claws • Horns and • hair

20. Vertebrate Characteristics, Continued • Notochord replaced by spinal column of vertebrae composed of • Cartilage • Bone • Both • Endoskeleton with • Cranium • Visceral arches • Limb girdles • Two pairs of jointed appendages

21. Vertebrate Characteristics, Continued • Muscles attached to skeleton • Complete digestive system ventral to spinal cord with • Digestive glands • Liver • Pancreas • Ventral heart with 2-4 chambers • Paired aortic arches feed gills in aquatic vertebrates • Modified aortic arch in terrestrial vertebrates form pulmonary system

22. Vertebrate Characteristics, Continued • Well-developed coelom with organs • Paired mesonephric or metanephric kidneys with ducts which drain waste to cloaca or anal region • Brain with 5 vesicles • 10-12 pairs of cranial nerves with sensory and motor functions; spinal nerves for each myomere • Autonomic nervous system controls involuntary functions of internal organs • Endocrine system of ductless glands scattered throughout body • Separate sexes with paired gonads • Head, Trunk, • Tail (some with necks) • Most with two pairs of appendages

23. Jawless Ostracoderms (Gr. Ostrakon = shell + derma= skin) • Earliest vertebrate fossils from Ordovician from Russia and U.S. • Bony armor over body • Earliest were heterostrachans • No paired lateral fins • Clumsy swimming • Bottom feeders • Developed dorsal spines and plates in Devonian • Dominated until cephalaspids

24. Cephalaspids • Evolved fins • Improved swimming ability • Died out when couldn’t compete with modern fishes

25. Early Jawed Vertebrates • Collectively called Agnathans • Jaws arose from modifications of first two repeated cartilaginous gill arches

26. Agnathans • 1st jawed vertebrates called placoderms (Gr. Plax = plate + derma = skin) • Better adapted for seizing food • Extinct by Paleozoic • Modern fishes evolved from agnathans

27. Superclass AgnathaClass Myxini (Hagfishes) • Hagfishes • 65+ known • Atlantic hagfish best known N.A. • Deep water • Feeds on marine invertebrates and dead fish • Sensory tentacles (barbels) around head • Degenerate eyes • Well-developed sense of smell • 12-15 pairs of gill openings • Numerous slime glands

28. Hagfishes • Fibrous & cartilagenous skeleton • Overhand knot • No lateral, anal or dorsal fins • Caudal fin extended dorsally and ventrally • Feed by rasping mechanism of keratinized teeth on tongue • No stomach • Method of reproduction unknown • Copenhagen Academy of Science (100 years) • No larval stage

29. Class Cephalaspidomorphi (Lampreys) • N.A. belong to family Petromyzontidae (Gr. Petros = stone + myzon = sucking) • Parasitic & nonparasitic species • Petromyzon marinus found on both sides of Atlantic • Feeding by circular oral disk with keratinized teeth • Cartilagenous • No lateral or anal fins, one dorsal • Caudal similar to hagfish • No stomach • Well developed eyes • Excellent sense of smell

30. Cephalaspidomorphi • Anadromos (fresh & salt water) • Male makes nest using sucker • Male attaches to side of female’s head and deposits sperms • Eggs sticky • Ammocoete larva produced (resembles Branchiostoma)

31. Superclass: Ganthostomata Jawed Fishes • Class Chondrichthyes (cartilagenous fishes) sharks, skates, rays • Approximately 850 species – vast majority marine • Some calcification of cartilage but never complete • Actually evolved from fish with bony skeletons, so retrograde evolution • Minerals with abundance of phosphate found in teeth, scales, spines

32. Chondrichthyes • With exception of chimeras, all have heterocercal tails • Paired pelvic and pectoral fins • 1 or 2 dorsal fins • Males have modified pelvic fins called claspers (internal fertilization)

33. Chondrichthyes • Placoid scales

34. Chondrichthyes • Spiral valve in stomach (except for Chimeras) • Slows passage of food • Increases surface area for absorption • Rectal glands to regulate salt balance • Well developed senses • Olfactory • Lateral lines • Ampullae of Lorenzini (electroreceptor) • Separate sexes with paired gonads • Oviparous, ovoviviparous, viviparous

35. Rays • Flattened body • Mostly bottom dwellers with jaws to crush prey • Gills and mouths typically on ventral surface with spiracle on dorsal surface • Skates, electric rays, sawfishes, stingrays, eagle rays and manta rays

36. Rays • Manta ray • Up to 120 feet, 1 ton • Plankton eater • Sting ray • Barbed spine near caudal fin • Electric rays • Glands on either side of head • 50 volts • Power may be 1 kilowatt

37. Sharks • With exception of whales, sharks are largest animal in Ocean • Whale shark – filter feeder • Basking shark – filter feeder • Smallest is the Dwarf Lantern fish Etmopteris peryii 7 1/2 – 8 inches

38. Dangerous Sharks • Most sharks may harm humans but do not necessarily seek humans out as a food source • Bull shark (Carcharhinus leucas) • On average, adult males are about 7 feet (2.1 m) long weighing 200 pounds (90 kg). Adult females are about 11.5 feet (3.5 m) long weighing 500 pounds (230 kg). • Habitat is tropical and subtropical oceans and seas along the coastlines. Also found in a few fresh water rivers and lakes.

39. Lemon Shark(Negaprion brevirostris) • Name from coloration on dorsal surface) • Found out the coast of the southeastern U.S. • May attack humans • It lives near the surface and at moderate depths, frequenting bays, docks, and river mouths.

40. Black Tip Shark(Carcharhinuslimbatus) Blacktip sharks are found in tropical to subtropical coastal, shelf, and island waters. In the Atlantic during their seasonal migration they range from Nova Scotia to Brazil, but their center of abundance is in the Gulf of Mexico and Caribbean Sea The blacktip shark inhabits inshore and offshore waters. Average adult size is around 150 cm (4.9 feet) weighing about 18 kg (40 lbs)

41. Tiger Shark(Galeocerdo cuvier) • Tiger sharks grow up to 20 feet (6 m). • Habitat: surface to 1,200 feet (340 m). In tropical waters worldwide and in some temperate seas. Inhabit both the shoreline and open waters. • Known to attack humans.

42. Great Hammerhead(Sphyrna mokarran) • Up to 3.5 m (11.5 feet) long. Largest reported 6 m (20 feet) • Average 230 kg (500 pounds) but can weigh as much as 450 kg (1,000 pounds) • Tropical & subtropical waters along the coastlines. over the continental shelves and the adjacent drop-off to depths of about 80 m (260 feet). • Great hammerhead can be dangerous

43. Nurse Shark(Ginglymostoma cirratum) • 0.75-4m (2-13 feet) long • Found in warm waters • Shallow-water sharks • Bottom-dwellers, living near sandy beaches, mudflats, and sandbars. Common in coral reefs. • Harmless unless provoked

44. Subclass: HolocephaliGhostfish or chimaeras • 31 living species – on their way to extinction • Deep waters off coastal areas • Jaws have flat plates (no teeth) • Upper jaw fused to cranium • Feed on seaweed, molluscans, echinoderms, crustaceans and other fish • Some are highly colored

45. Class OsteichthyesBony Fish • 96% of all living fishes • Bone arises from endochondral bone (from cartilage) • Gills, lungs, swim bladders • Gills covered by bony plate called operculum

46. Lob-finned Fishes • Some consider these significant evolutionarily because of well-developed fins resemble limbs • Coelocanths • Considered extinct until 1938 • Specimen found off coast of South Africa Latimeria chalumnae • New species off Indonesia in 1998

47. Subclass DipneustiLungfishes • Also lobe-finned, mostly extinct • Three extant • Skin in all covered with heavy scales similar to dentine in teeth – called cosmine

48. Lung development

49. Subclass ActinopterygiiRay-finned Fishes • Largest group of fishes • Named from dermal rays spreading from base of each fin • One of three types of scales: • Ganoid, cycloid, ctenoid (in order of evolution)

50. Actinopterygii • Swim bladders may or may not be present