lecture #2 - august 27, 2008 reading for today: pgs. 10-14, 151-157,197-204
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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 & homologies b. swapping branches 3. Defining Characters of Cepahlochordates, Myxiniformes, Petromyzontiformes, & Gnathostomata - PowerPoint PPT PresentationTRANSCRIPT
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?