Lecture 3 - Friday, August 29, 2008. 1. Finish lampreys and fossil forms of jawless fishes 2. Evolution of jaws and pa

1. Lecture 3 - Friday, August 29, 2008. 1. Finish lampreys and fossil forms of jawless fishes 2. Evolution of jaws and paired fins 3. Other Fossil Fishes 4. Distinguishing characters of Chondrichthyes & Osteichthyes a. explanation traits (fin rays, scales, claspers, teeth in rows) 5. Other characters of Chondrichthyes (show shark video) 6. Distinguishing Characters of Elasmobranchii & Holocephali Gnathostomata Chondrichthyes Osteichthyes Petromyzontiformes Myxiniformes

2. We are going out in the field next Tuesday. Please meet at the Shelford Vivarium.Corner of Healey & Wright Street. We will leave at 1pm. Be there or be square. I will send out an e-mail next Monday/Tuesday morning to remind all of you.

3. Petromyzontiformes – Lampreys (Lampetra fluviatilis)

4. Lamprey Distribution

5. Parasitic Lamprey life cycle Eggs hatch in 12-14 days Ammocoete stage

6. Nonparasitic Lamprey life cycle Eggs hatch in 12-14 days Ammocoete stage Free living species metamorph into adults and immediately return to spawning site to mate and then die

7. Chestnut Lamprey (Ichthyomyzon castaneus)

8. European Brook Lamprey (Lampetra planeri)

9. lamprey video1 lamprey video2 funny lamprey video

10. Sea Lamprey, Petromyzon marinus • Anadromous species native to both sides of the • North Atlantic • Large parasitic species (up to 3’), can kill up to • 40 lbs. of prey in lifetime • Classic example of the deleterious effects of • an exotic species initiated by man-made habitat • alterations • But also one of the few examples of successful • control of exotic species

11. Sea Lamprey, Petromyzon marinus First reported in 1890 but may be native

12. Sea Lamprey, Petromyzon marinus First reported in 1890 but may be native Niagara Falls served as barrier to dispersal

13. Welland Canal was built to allow ships to get around Niagara Falls

14. Sea Lamprey, Petromyzon marinus First reported in 1890 but may be native 1946 Niagara Falls served as barrier to dispersal 1936 1921

15. Sea Lamprey, Petromyzon marinus Control measures • Physical barriers to spawning streams • Releasing sterilized males • Application of a lampricide (TFM) - poured into streams • known to harbor ammocoetes, specific to ammocoetes

16. Sea Lamprey, Petromyzon marinus

17. Ostracoderm from Ordovician (450 MYA)

18. Ostracoderms paraphyletic group (actually two groups) • No jaws • The first vertebrates- cartilaginous internal skeleton • Bony exoskeleton armor-1st true bone (dermal) • First ones were small (< 15 cm) • No paired fins • Bottom dwellers • Lots of Diverse forms

19. ?

20. Where did the jaws come from?

21. Many different arrangements evolved in different groups.

22. Placoderms - many families, very abundant - armored fishes with jaws that had paired fins - probably first jawed vertebrate

23. Nuchal joint = ‘craniovertebral joint’ - could open their mouths VERY wide to eat prey

25. Acanthodii - “Spiny sharks” - thought to be sister group to Osteichthyes - important for “folded fin theory” - also appeared early & were abundant

26. Order and Abundance Jawless fishes came first. BUT placoderms, Acanthodians, & Sharks & Co. show up at a very similar time. Makes it difficult to work out ancestor - descendant relationships.

27. Chondrichthyes synapomorphies 1. Pelvic claspers • Derived from the margin of the pelvic fin

28. Cool Shark Videos to Checkout Mating Sharks Video 1 Mating Sharks Video 2

29. Chondrichthyes synapomorphies • Teeth not fused to jaws • Replaced serially in whorls

31. Chondrichthyes synapomorphies 3. Skull (chondrocranium) lacks sutures

32. Elasmoid Placoid Ganoid enamel dentine Cosmoid bone 9

34. heterocercal abbreviated heterocercal isocercal homocercal 8

35. Bull Shark with heterocercal tail

36. Major living gnathostome lineages

37. Subclass Holocephali Ratfishes, rabbitfishes, or chimeras Order Chimaeriformes (58 species)

38. Subclass Holocephali Ratfishes, rabbitfishes, or chimeras

39. Subclass Holocephali Differ from sharks and rays by: • lacking gill slits - a single gill covering over 4 gill openings • Upper jaw fused to cranium • skin is naked in adults • Some males have cephalic claspers in addition to pelvic ones

40. Order Chimaeriformes • Ecology, Life History • Reproduction, oviparous (egg-laying), internal fertilization • Benthic, deep sea (80 to 2600 m), around the world • Nocturnal • Feed mainly onbenthic invertebrates

41. Review Questions 1. Which structures did jaws evolve from? Which structures did paired fins evolve from? What is the importance of Acanthodii in relationship to the “folded fin theory”? Why is the evolution of jaws considered to be a major innovation of vertebrates? What were the ecological consequences of the evolution of jaws? What were the ecological consequences of the evolution of paired fins? 2. Who were the placoderms and what advantages did they have over the Ostracoderms? What two traits did they lack that might have placed them at a disadvantage in terms of feeding? 3. To what extent does the fossil record give us a complete picture of the history of the evolution of fishes? What are some of the difficulties of working with fossils? Did you read pages 175-176? 4. On page 194, your book shows a picture of skin thickness of male and female blue sharks. Which sex has thicker skin? What is the proposed reason for this? 5. Draw out the phylogenetic tree for Myxiniformes, Petromyzontiformes, Chondrichthyes, and Osteichthyes. Indicate which groups are Gnathostomata. Draw the synapomorphies onto the branches of the tree. Describe lepidotrichia vs. ceratotrichia, claspers, and placoid scales. Also list the type of skeleton, presence/absence of swimbladder or lungs, solid cranium, and teeth replaced as rows.

42. Review Questions (Cont’d.) 6. What traits distinguish the Elasmobranchii from the Holocephali? Who are the Holocephali? Where do they live? How do they reproduce? How many species are there?