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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
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Lecture #2 - August 27, 2008Reading 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 - notochord, cranium, 3-part brain, nephrons, lateral line, unpaired fins, paired fins, vertebrae, jaws, gill pouches 4. Details on hagfish 5. Details on lampreys 6. (time permitting) details on jawless fossil fishes
Homology - Possession by two or more species of a trait derived, with or without modification, from their common ancestor Humerus Radius and ulna Carpals Metacarpals Phalanges Bird Bat Turtle Human Horse Seal
Group Exercise - make a tree from these data, assume that taxa E is the outgroup. Also assume that all characters are informative.
Cephalochordata important point in this picture is there is no brain and no cranium. The nerve cord just ends. Compare to picture of hagfish & lamprey.
Gills: Agnatha 5-16 gill pouches 7 gill pouches hagfish lamprey
look at different types of fins - anal, caudal, dorsal pectoral, pelvic
Lateral line in fishes A system of mechanoreptors that detect water movement 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)
Petromyzontiformes – Lampreys (Lampetra fluviatilis)
Parasitic Lamprey life cycle Eggs hatch in 12-14 days Ammocoete stage
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
New Zealand Lamprey(Geotria australis) Chestnut Lamprey (Ichthyomyzon castaneus)
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 1890 but may be native
Sea Lamprey, Petromyzon marinus First reported in 1890 but may be native Niagara Falls served as barrier to dispersal
Welland Canal was built to allow ships to get around Niagara Falls
Sea Lamprey, Petromyzon marinus First reported in 1890 but may be native 1946 Niagara Falls served as barrier to dispersal 1936 1921
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
lamprey video1 lamprey video2 funny lamprey video
Ostracoderm from Ordovician (450 MYA)
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?
