Notes on the presence of a single sperm duct in Procambarus clarkii (Girard, 1852) (Decapoda: Cambaridae) from Italian waters

The present work deals with the discovery of a distinctive morphology in the male reproductive apparatus of the red swamp crayfish, Procambarus clarkii (Girard, 1852), from two Italian lakes (where it was introduced a few years ago from different foreign countries). Anatomy and histology of the male reproductive apparatus were investigated in a large sample of the crayfish populations. Males were characterized by the presence of a tri-lobate testis and, as a rule, of a single sperm duct (on the right body side). Furthermore, a comparison of the same anatomical structures was made taking into consideration two other crayfish species: Astacus leptodactylus and Orconectes limosus. Observations on these crustaceans showed a bi-lobate testis and no morphological differences between the normally developed left and right vasa deferentia. The presence of a single sperm duct and of three testicular lobes in P. clarkii might be related to its burrowing-reproductive habit. One single vas deferens may be an adaptation to burrow environments where copulation is not affected by water flow, while three testicular lobes may act as a mechanism to make the spermatogenetic process active all year round, thus enhancing the probabilities of success in reproduction.