Patterns of Sperm Transfer Behavior in a Pholcid Spider with Two Distinct Copulatory Phases
Sexual selection is the responsible force for the evolution and maintenance of genital diversity and function. This is the case for example, of genital movements performed by males during mating and copulation duration. Spiders perform ritualized copulations whereby males carry out different types of movements using their pedipalps with varying duration. The function and duration of these pedipalp movements is unclear. In the pholcid spider, Holocnemus pluchei males that copulate with virgin females perform two copulatory phases: phase I in which the pedipalps move and phase II in which pedipalps remain motionless. Using H. pluchei as a study species, our study aims were: 1) to assess if sperm transfer occurs when pedipalps move or are still and quantify the number of sperm in male bulbs and in the female uterus externus after copulation; and, 2) to determine if amount of sperm transferred to females is associated with duration of each copulatory phase. Two experimental groups (i. e. complete copulation and interrupted copulation) were established in which the amount of sperm remaining in the male bulbs and the amount of sperm stored by females were determined. Our results show that sperm transfer occurs during phase I, that males transfer almost all sperm from their bulbs while the females store only 20% of that male amount. There was no relation between the amount of sperm transferred or stored and the duration of the copulatory phases. These results support the hypothesis that while both phases may serve a copulatory courtship, only phase I (when pedipalps move) serves for sperm transfer.
KeywordsMating sperm transfer spermatozoa Holocnemus pluchei sexual selection
We thank Camilo I. Mattoni, Alejandra Ceballos and Matias Izquierdo for their useful comments to previous versions of this paper. We also thank Fedra Bollatti, Macarena González, David Vrech, Paola Olivero and Natalia Rivetti for their help during collecting trips. We also thank the Jardín Zoológico de Córdoba and the Universidad Nacional de Córdoba for allowing us to collect the samples. Mathias Foellmer and an anonymous referee provided helpful and constructive comments which improved the manuscript. Financial support was provided by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Fondo para la Investigación Científica y Tecnológica (FONCYT) and Secretaría de Ciencia y Tecnología de la Universidad Nacional de Córdoba (SECYT).
Compliance with Ethical Standards
This study was conducted in compliance with the “Guidelines for the use of animals in research” as published in Animal Behaviour (1991, 41, 183–186), and with the laws of the country where the research was conducted.
Conflict of Interest
The authors declare that they have no conflict of interest.
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