Nuptial gift-giving behaviour and male mating effort in the Neotropical spider Paratrechalea ornata (Trechaleidae)

The occurrence of nuptial gifts is rare in spiders, being well known only for a single species, Pisaura mirabilis (Pisauridae), whose males offer females a prey wrapped in silk during courtship. Although some males can mate without offering a prey, the gift in this species is thought to represent male mating effort. Male gift offering has been recently described in Paratrechalea ornata, a Neotropical spider belonging to another family, Trechaleidae. We investigated the function of the gift in this species by testing the mating effort hypothesis and two other nonexclusive hypotheses, sexual cannibalism avoidance and paternal investment. Two groups of males were exposed to virgin females: 23 males with no prey (NP group) and 21 males carrying a prey (CP group). Mating success, courtship, copulation and first oviposition were recorded. Males from group CP had better mating success, longer copulations and longer palpal insertions than those from NP. Longer copulations were associated with earlier eggsac construction and oviposition. Some unmated males from NP wrapped prey carrion when they returned to their breeding jars after the trial. Our findings suggest that nuptial gift giving represents male mating effort for P. ornata. Nuptial gifts would allow males to control copulation duration and to accelerate female oviposition, improving sperm supply and paternity, and minimizing possible costs of remating with polyandrous females.