The way of the samurai snail.

Sexual selection favors strategies that enhance the fertilization chances of sperm donors, and sexual conflict can ensue when these adaptations negatively affect sperm recipients (Arnqvist and Rowe 2005). Such conflict often causes counteradaptive coevolution that can result in bizarre mating behaviors in separate-sex (Arnqvist and Rowe 2005) and hermaphroditic species (Michiels and Newman 1998; Koene et al. 2005). For simultaneous hermaphrodites, dart shooting is perhaps the best known of these sexually selected behaviors, and a recent comparative study supports morphological counteradaptive coevolution (Koene and Schulenburg 2005; Schilthuizen 2005). However, everything that is known about dart-shooting behavior is based almost entirely on a single species, the garden snail Cantareus aspersus (formerly Helix aspersa). The inclusion of other dart-bearing species in evolutionary studies may enable more general, broader inferences. Therefore, here we provide the first description of the unique dartshooting behavior performed by the Japanese snail Euhadra subnimbosa. Dart shooting in C. aspersus consists of stabbing a 9-