Morphology and function of the copulatory system in freshwater crabs of the genus Potamon

To understand the reproductive processes of freshwater crabs of the genus P otamon, we examined the first and second gonopod and the gonoducts of the f emale by histological methods. The gonopods are highly modified compared to those of other brachyuran crabs. In particular, the second gonopod is unus ually long and has a special morphology, ending in a long sclerotized tube. Suggestions for the function of both gonopods and their different parts ar e presented. Tubulation of the first and second gonopod is observed. Rosett e glands, which are abundant in the subterminal joint of the first gonopod, are connected to the sperm channel by cuticular pores. In females, the chi tinous parts of the inner vulva may prove to have a more constant morpholog y than the external flexible structures. (C) 1999 Wiley-Liss, Inc.