Genital movements are not restricted to spermatozoa transfer in a haplogyne spider

Abstract

Internally fertilized animals are characterized by the transfer of their spermatozoa during copulation. However, the duration of copulation is highly variable, which suggests that they may serve for other functions apart from spermatozoa transfer. For example, during copulation, males can stimulate the female by using genitalic movements and/or by positioning their spermatozoa adequately within the female genitalia. In the spider Holocnemus pluchei, males perform strong squeezes and torsion movements with their pedipalps (part of their genitalia actively related to copulation) inside the female genitalia and transfer their spermatozoa during Phase I of copulation. However, the exact moment in which such transfer occurs and its relation to the pedipalp movements are still unknown. Herein, we first have identified the precise moment when the spermatozoa transfer occurs during phase I and its relation to genital movements by interrupting mating couples at the beginning, at middle and at end of this phase. Subsequently, the spermatozoa number remaining in male genitalia and stored in female genitalia were counted. We detected no relation between the number of genital movements and the spermatozoa number present in both, female and male genitalia and body size. As stated above, male genital movements serve another role during copulation in addition to spermatozoa transfer in a context of post-copulatory sexual selection; most likely, they stimulate the female in a cryptic female choice framework.