CONICET | Buscador de Institutos y Recursos Humanos

Male genital mutilation is a common mechanism by which males reduce sperm competition by plugging the female insemination ducts with different parts of its own genital system. This behavior is frequent in many spider families but is uncommon in Haplogynae. The reproductive biology of Dysderoidea is not well studied and the data are fragmentary; male genital mutilation has been reported only for one species of Oonopidae. This study provides evidence of male genital mutilation in the genus Unicorn Platnick & Brescovit 1995 (Araneae: Dysderoidea: Oonopidae). Remains of the embolus were found in the female posterior receptaculum. This behavior could be a strategy used by the males in order to guarantee the paternity and not for escape from female attacks, as has been reported for other species of Araneae since cannibalism is unlikely in this species. The presence of the embolus in the structure suggests that this is the first place where the sperm is received. The similarity of the female genitalia of Unicorn with those of Orsolobidae, and the sclerotization of the seminal duct in the male copulatory bulb, characters also present in Orchestina, Xiombarg and Orsolobidae, are strong evidence of the basal position of this genus in the family Oonopidae.