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 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
Recent genetic data indicates that it may be native to Lake Ontario
Direct connection to Atlantic

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
Application of lampricide is primary measure used

16. Sea Lamprey, Petromyzon marinus
As it moved up the Great Lakes it developed an appetite for commercially important species such as lake trout and whitefish, most die from blood loss
This graph shows percentage of historic abundance of lake trout
Overharvesting may have also played role here
This is what is different about this exotic species, since it has having a noticable impact on peoples pocket books a lot of money was spent
Unlike carp, round goby……

17. Ostracoderm from Ordovician (450 MYA)
Shallow seas in or estuarine habitats in tropical and subtropical regions of Gondwana and Laurasian Supercontientns

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
A sperm transfer organ, sharks have internal fertilization, but both lay eggs (43% of spp.) or have life birth (57% of species)
Tough to see whats going on in this pict. But the male is holding the female by biting one of her pectoral fins and inserting on his claspers in her cloaca
Female shark skin may be up to 3 times thicker, biting can take place on parts of female
What is amazing given given the low level of diversity of species, is the extreme diversity of reproductive strategies shown by sharks

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. abbreviated heterocercal
isocercal
homocercal 8

35. Bull Shark with heterocercal tail

36. Major living gnathostome lineages

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

38. Ratfishes, rabbitfishes, or chimeras
Subclass Holocephali
Ratfishes, rabbitfishes, or chimeras

39. Differ from sharks and rays by:
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
Purpose of tentaculum is unknown

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 on benthic 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 ?
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?