| Research Abstract |
Internal fertilization is an efficient form of reproduction, but requires male and female anatomical specializations. While external fertilization is the general rule for fish, certain cartilaginous and bony fish reproduce by internal fertilization, having an anal fin modified into a copulatory organ, the gonopodium. Most birds copulate by placing their cloacas in contact for the transfer of sperm, but some avian species possess elaborate male copulatory organs. All mammals utilize internal fertilization, and as a consequence ; reproductive efficiency is increased.
As for mammals (mouse), we have shown already shh (sonic hedgehog)-/-mutant mice displayed complete external genitalia agenesis suggesting its importance for the "developmental field" formation as cloaca. In this study, we have shown that in avian system, shh expression is also observed during cloaca formation. It was shown by this study that Bmp may function during cloaca formation which may interact with shh pathway. With the help of our recent established technique, sonoporation, we are further analyzing functions of various factors for cloaca formation in birds. For fish system, we have shown that shh is expressed and functions in the distal region of gonopodium, as copulatory organ derived from anal fin. We have shown that Shh functions for the outgrowth regulation of such gonopodium. These studies suggest the importance of some "shared developmental mechanisms for copulatory organ formation" in diverged animal species.
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