Questions and Answers for Comparative Vertebrate Anatomy

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Swim bladder: Kardong (textbook) takes the conservative stand of not concluding homology. However, the statement "some morphologists take thes similarities ..... are homologous" on pag. 403 (left column, 11 lines or so from bottom), could be more accurately phrase "MOST morphologists....". ALso, the relationship of lungs to swim bladders is more apparent in Fig. 11.5 where forms have a lung or a swim bladder, but not both. The reference of the swim bladder of halecomorphi and ginglymodi as being a lung (as implied by the figure) is not how most would put it - all the actinopterygii have a swim bladder (derived from lung) or have lost it. I discussed the teleosts tubes in class, primarily. The argument is this: Teleosts are mostly external fertilizers. They produce small, zooplanktonic larvae. The low probability of success of recruitment of new adult fish due to both of these limiters (many eggs not getting fertilized when they are simply sprayed into a cloud of milt or sperm and the high mortality of zooplankton) means the ovaries of many teleosts are HIGHLY productive (milllions of eggs per reproductive event, many events per breeding season). So, the full enclosure of the ovaries in a new Ovarian Duct (without passage of eggs thru coelom) is much more efficient for the production of millions of very small eggs. Chance of eggs getting lost in the coelom is reduced to zero. Dr. Coughlin

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1. delta p can be manipulated in a number of ways. Not all are for instantaneous maximization of delta p. For instance, the counter-current flow of blood and water in the secondary lamellae of fishes maximizes respiration rate by setting manipulating delta p (constant delta p across the entire lamellae). THe unidirectional air flow in the birds lungs can be thought of doing the same way. The common ancestor of mammals and birds were the stem reptiles, members of the subclass anapsida that are called captorhinids (or cotylosaurs). Of course their hearts are not fossilized, but a variety of hearts are derived from them - mammals along one line, squamates/chelonia along another. Crocodyles are presumably derived from some pre-squamate heart. Birds are presumably derived from the crocodyle like heart. So, importantly, the solutions to fully obligatory double circulation in birds and mammals are clearly homoplastic. While we can't be sure what cotylosaur hearts looked like, they definitely were not fully separated in double circulation like birds or mammals.

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The 3 primary characteristics that affect muscle design and function that were discussed in class, but not explicitly in the book, are: 1. relaxation rate of muscle 2. the sarcomere length tension curve 3. the power (and force) vs. velocity curve. We reviewed this material again on friday in class. This material is discussed somewhat in the early parts of the muscle chapter of the book. The branchiomeric muscles and other head muscles were the most comprehensively covered in class. The axial muscles are a relatively simple story. The appendicular muscles were also discussed in a more general fashion. I won't tell you to not study one or the other, but the head muscles were the most well covered in both class and the book.

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Gaits: gaits are not discussed explicitly with the muscle chapter, but are found in the chapter on appendicular (?) skeleton. There are several graphics and other information on different types of gaits in tetrapods and mammals. The muscle lecture handout included a listing of the pages that are relevant. That listing can also be found in the annoucement section of the virtual office hours. Furbringer: It is true that the text book does not use "furbringer" in explicitly describing the hypothesis. However, there is some discussion of innervation, particular of the branchiomeric musculature.

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