On the male-effect in the terrestrial Crustacean Armadillidium vulgare (Latreille, 1804)

In the terrestrial Crustacean Armadillidium vulgare, the onset of female reproduction can be sped up by a male-induced stimulation. This male-effect is mainly characterized by a shortening of the vitellogenesis period, which occurs during the preparturial intermoult. The determinism of this phenomenon, for the first time reported by Jassem in 1982, was investigated here by both experimental and ethological approaches. It was shown that a male deprived of its copulatory organs is significantly less stimulating than an integrated one. On the other hand, a paired female with obturated genital apertures is significantly less stimulated. According to the literature, mating takes place only when vitellogenesis is nearly over and therefore cannot be related to the male-effect. Nevertheless, the ethological approach has revealed that females are early attractive for males, and that mating postures can be observed during the whole preparturial intermoult. In fact, insemination can happen as early as the initiation of the secondary vitellogenesis. Before this stage, short mating postures are still observed but no sperm was found in the female genital ducts (pseudocopulation). However, spermatozoa and other seminal substances are not implicated in this phenomenon since a male unable to ejaculate is as efficient as a normal one. Therefore, it is strongly assumed that the male-effect results from mating postures during which male copulatory organs act on mechanoreceptors located in the female genital apparatus.