Comparative reproductive biology of Ariolimax californicus and A. dolichophallus (Gastropoda; Stylommiatophora)

Summary

Traits which differ among species in a genus are considered to be the product of relatively rapid evolution. Laboratory studies indicate that copulation differs between two species of the banana slug Ariolimax with A. dolichophallus having a pattern of a single, long duration (typically greater than 1 h) intromission which is simultaneously reciprocal, and A. californicus having mating encounters typically involving a bout of brief (typically 10–20 min) unilateral intromissions. Reciprocal apophallation was observed for both species. Field observations confirm simultaneously reciprocal copulation and apophallation in A. dolichophallus. Mating was more frequent in the spring and summer months. In laboratory studies the two species also differed in life history parameters; mean growth rate was greater in A. californicus than A. dolichophallus, whereas eggs are larger in A. dolichophallus (range = 0.33–0.5 g; n=59) than in A. californicus (range= 0.08–0.27 g; n=164).