Copulatory behavior in a pholcid spider: males use specialized genitalic movements for sperm removal and copulatory courtship

Abstract

Sexual selection may operate on pre-copulatory, copulatory, and post-copulatory traits. An example of a copulatory target of sexual selection is the genitalic movements a male performs during copulation. These movements may function either to prevent sperm competition or to influence a female's fertilization decision. Here we investigated how copulation duration, pedipalp movements, and abdominal movements that males of the pholcid spider Holocnemus pluchei produce during copulation influence sperm removal and/or patterns of successful sperm transfer. We compared mating events with virgin and mated females for differences in copulatory and post-copulatory behavior. We expected longer copulation duration, longer pedipalp movement duration, and more complex and frequent pedipalp and abdominal movements when males mated with mated females compared to virgin females. Except for abdominal movements, our results corroborated these predictions. Furthermore, when we investigated mating events with mated females, we observed sperm mass ejection from the female gonopore and physical removal of sperm by males' procursi. Females with interrupted second mating events showed a significant reduction of stored sperm masses compared to females with completed mating events. We suggest that males use alternating pedipalp movements to remove most of the rival sperm stored by mated females prior to sperm transfer. Copulation duration and pedipalp movements can be further used to transfer sperm and/or as a form of genitalic copulatory courtship.

Copulatory and Post-copulatory Sexual Selection in Haplogyne Spiders, with Emphasis on Pholcidae and Oonopidae

“…In Pholcidae, the male courts the female in her web by performing bursts of quick dorsoventral vibrations with the opisthosoma when moving toward her (Huber 1994(Huber , 1995Huber and Eberhard 1997;Calbacho-Rosa et al 2013). Females that allow copulation respond with tapping movements and move a short distance toward the approaching male.…”

“…Before the insertion, the pedipalps are twisted again through a further 90°, resulting in a total torsion of 180°. Both pedipalps are kept inserted in the female genital cavity during copulation and the male performed rhythmic twisting movements during the entire copulation, simultaneously or alternately (Calbacho-Rosa et al 2013;Huber and Eberhard 1997;Schäfer and Uhl 2002).…”

“…The frequency of movement of male pedipalps varies along copulation, being higher at the beginning (Calbacho-Rosa et al 2013), and copulations with mated females are longer than those with virgin ones. Males use cheliceral apophyses and palps to grasp the epigynum (Fig.…”

“…For example, H. pluchei males engaged in longer mating events and Yes (sperm dumping) Burger et al (2003) more abdominal movements when mating with mated females than with virgin females (Calbacho-Rosa et al 2013). Males could stimulate mated females using abdominal vibratory movements as a form of copulatory courtship.…”

“…For example, in P. simoni, the first minutes of copulation are characterized by intensive leg movements, in which the male seems to stroke back the fidgeting female legs with his legs (Huber 1994). Similarly, males of P. globosus (Huber and Eberhard 1997) and H. pluchei (Calbacho-Rosa et al 2013) during copulation performed occasional leg vibrations. Other less studied cases in haplogynes include Sicarius sp.…”