Lecture #2 - August 27, 2008 Reading for Today: pgs. 10-14, 151-157,197-204

Lecture #2 - August 27, 2008 Reading for Today: pgs. 10-14, 151-157,197-204

1. A few more phylogenetic terms.2. Building a tree

a. synapomorphies & homologiesb. swapping branches

3. Defining Characters of Cepahlochordates, Myxiniformes, Petromyzontiformes, & Gnathostomata

- notochord, cranium, 3-part brain, nephrons, lateral line, unpaired fins, pairedfins, vertebrae, jaws, gill pouches

4. Details on hagfish5. Details on lampreys6. (time permitting) details on jawless fossil fishes

Jawless Fishes

Homology - Possession by two or more species of a trait derived, with or without modification, from their common ancestor

Turtle Human Horse Bird Bat Seal

Phalanges

Humerus

Radius and ulnaCarpalsMetacarpals

taxa # eyes # heads # toes # fingers # stomachs # fins

A 1 1 1 1 2 1

B 1 1 0 1 1 1

C 1 1 1 1 1 1

D 0 1 0 1 1 1

E 0 0 0 0 1 1

Group Exercise - make a tree from these data, assume that taxa E is theoutgroup. Also assume that all characters are informative.

Notochord on Cephalochordate (Amphioxus)

Cephalochordata

important point in this picture is there is no brainand no cranium. The nerve cord just ends. Compareto picture of hagfish & lamprey.

hagfish

lamprey

Gills: Agnatha

lamprey hagfish

7 gill pouches

5-16 gill pouches

look at differenttypes of fins -anal, caudal, dorsalpectoral, pelvic

lamprey - only has dorsal and caudal fin

Lateral line in fishes

A system of mechanoreptors that detect watermovement or pressure change near fish’s body

Neuromasts - made up of individual hair cells

Living Representatives of Ancient Fishes

• Phylum Chordata– Subphylum Vertebrata

•Superclass Agnatha– Class Myxini

»Order Myxiniformes hagfishes (43 sp.,

marine)– Class Cephalaspidomorphi

»Order Petromyzontiformes lampreys (41 sp.,

freshw. & anadromous)

Hagfish Distribution

Pacific Hagfish (Eptatretus stoutii)

Inshore Hagfish (Eptatretus burgeri)

Pacific Hagfish (Eptatretus stoutii)

Inshore Hagfish (Eptatretus burgeri)

Eelskin - “silk of the Ocean” - made from skin of hagfish

Petromyzontiformes – Lampreys

(Lampetra fluviatilis)

Lamprey Distribution

Eggs hatch in 12-14 days

Am

mo

coete stag

e

Parasitic Lamprey life cycle

Eggs hatch in 12-14 days

Am

mo

coete stag

e

Free living species metamorph into adults and immediatelyreturn to spawning site to mate and then die

Nonparasitic Lamprey life cycle

Chestnut Lamprey (Ichthyomyzon castaneus)

Chestnut Lamprey (Ichthyomyzon

castaneus)

New Zealand Lamprey

(Geotria australis)

European Brook Lamprey (Lampetra planeri)

European Brook Lamprey (Lampetra planeri)

American Brook Lamprey (Lampetra appendix)

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

Sea Lamprey, Petromyzon marinus

First reported in 1890but may be native

Sea Lamprey, Petromyzon marinus

First reported in 1890but may be native

Niagara Falls served as barrier to dispersal

Welland Canal was built to allow ships to getaround Niagara Falls

Sea Lamprey, Petromyzon marinus

First reported in 1890but may be native

Niagara Falls served as barrier to dispersal

19211936

1946

Sea Lamprey, Petromyzon marinus

Sea Lamprey, Petromyzon marinusControl measures

•Physical barriers to spawning streams

•Releasing sterilized males

•Application of a lampricide (TFM) - poured into streams known to harbor ammocoetes, specific to ammocoetes

lamprey video1

lamprey video2

funny lamprey video

Ostracoderm from Ordovician(450 MYA)

Maisey, J. G. 1996. Discovering fossil fishes. HenryHolt and Co., New York.

Ostracoderms

paraphyletic group (actually two groups)

• Appeared in Cambrian/Ordovician, extinct in Devonian

• No jaws

• The first vertebrates- cartilaginous internal skeleton

• Bony exoskeleton armor-1st true bone (dermal)

• First ones were small (< 15 cm)

• No paired fins, some with reverse hypocercal tail

• Bottom dwellers

• Lots of Diverse forms

?

Review Questions

1. Give the character states for notochord, cranium, 3-part brain, vertebrae,nephrons, gills/gill pouch, semi-circular canals, lateral line, jaws, paired fins,and unpaired fins for Cephalochordates, Myxiniformes, Petromyzontiformes,and Gnathostomata. Draw the phylogenetic tree and show the nodes of the tree where each character is informative. Be able to draw the same tree, but in multiple forms (i.e. rotate the branches). Be able to briefly describe each trait.

2. What evidence is there to suggest that lampreys are closely related to Cephalaspidiformes? (i.e. have you read pages 153-157)

3. Who were the conodonts and what is their significance in the evolution of fishes? List 2 or 3 things. (see Box 11.1)

Note: a possible paper topic is listed on pages 156-157 on “Later Evolution of Primitive Agnathous Fishes”.

4. Why is the placement of hagfish in vertebrates a controversy? Do you consider hagfish to be a “fish”?

5. Where do hagfish live and what are the abiotic conditions under which they are found?

Review Questions (Cont’d.)6. Describe the life-cycle of lampreys. How does this differ between parasitic and non-parasitic species?

7. Some folks have hypothesized that non-parasitic species have repeatedly evolved from parasitic species. What is the evidence for this? Assuming that this is true, draw the phylogenetic tree that this pattern would produce?

8. Compare and contrast Myxiniformes and Petromyzontiformes. Describe their habitats, distribution, heart(s), vision, pineal gland, gill pouches, vertebrae (or lack there of), and guts.

9. What is the purpose of hagfish slime? List 3-4 ideas.

10. Describe the sequence of events that happened upon the construction of the Welland Canal. Why did the construction of this canal decimate Lake Trout and Whitefish populations in Lake Michigan? What is being done to counteract this? How do the conservation efforts specifically target lampreys? What effect do you think that this might have on non-parasitic lampreys?

11. Describe the hagfish fishery that has developed in recent years.

12. Who were the Ostracaderms? In what ways were they different and in what ways were they similar to hagfish and lampreys? Who was Mayomyzon?