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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 & homologiesb. swapping branches
3. Defining Characters of Cepahlopods, 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
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.
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
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
Gills: Agnatha
lamprey hagfish
7 gill pouches
5-16 gill pouches
Lamprey life cycle
Eggs hatch in 12-14 days
Am
moc oe te s ta ge
Lamprey life cycle
Eggs hatch in 12-14 days
Am
moc oe te s ta ge
Free living species metamorph into adults and immediatelyreturn to spawning site to mate and then die
Lamprey life cycle
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
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 thetree where each character is informative. Be able to draw the same tree, butin 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)
Who were the conodonts and what is their significance in the evolution offishes? List 2 or 3 things. (see Box 11.1)
Note: a possible paper topic is listed on pages 156-157 on “Later Evolutionof Primitive Agnathous Fishes”.