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Nephilid spider eunuch phenomenon induced by female or rival male aggressiveness Matjaz Kuntner1,2

Summary: Nephilid spider eunuch phenomenon induced by female or rival male aggressiveness
Matjaz Kuntner1,2
, Ingi Agnarsson1,2,3
and Matjaz Gregoric1
: 1
Institute of Biology, Scientific Research Centre, Slovenian
Academy of Sciences and Arts, Novi trg 2, P. O. Box 306, SI-1001 Ljubljana, Slovenia. E-mail: kuntner@gmail.com;
Department of Entomology, National Museum of Natural History, Smithsonian Institution, NHB-105, PO Box 37012,
Washington, DC 20013-7012, USA; 3
Department of Biology and Integrated Bioscience Program, University of Akron,
Akron, OH 443253908, USA
Abstract. Plugging of female genitals via male sexual mutilation is a common sexual repertoire in some nephilid spiders
(Herennia, Nephila, Nephilengys), but the behavioral pathways leading to emasculation are poorly understood. Recent
work suggests that copulating Herennia males damage their reproductive organs during copulation and then voluntarily,
and stereotypically, remove their pedipalps to become eunuchs. Presumably, such emasculation increases agility allowing
the male to better fend off rival males. However, through our observation of male antagonism in Nephilengys borbonica
(Vinson 1863) in La Reunion (Indian Ocean), we discovered that genital severance involving the entire male palp is induced
by a rival eunuch. Additionally, laboratory matings of the same species from Mayotte provide the first observations of
female sexual cannibalism in this species, one such forceful copulation termination leading to emasculation of the entire


Source: Agnarsson, Ingi - Department of Biology, Universidad de Puerto Rico


Collections: Biology and Medicine