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Pattern of sperm transfer in redback spiders: implications for sperm competition and
 

Summary: Pattern of sperm transfer in redback spiders:
implications for sperm competition and
male sacrifice
Lindsay S. E. Snow and Maydianne C. B. Andrade
Department of Life Sciences, University of Toronto at Scarborough, 1265 Military Trail,
Scarborough, ON, M1C 1A4, Canada
Many sperm competition studies have identified copulation duration as an important predictor of paternity. This result is often
interpreted as a sperm transfer effect--it is assumed that sperm transfer is limited by copulation duration. Here we test the
assumption of duration-dependent sperm transfer in the Australian redback spider, Latrodectus hasselti, in which a correlation
between copulation duration and paternity has been implicated in the evolution of a rare male self-sacrifice behavior. Male redbacks
facilitate sexual cannibalism by females during copulation. Sexual cannibalism is apparently adaptive for redback males, in part
because it results in longer copulations (25 versus 11 min.), and copulation duration is positively correlated with paternity. We
assessed sperm transfer in normal copulations and in copulations that we terminated at 5, 10, or 20 min. Our results show that the
paternity advantage of sexual cannibalism is not owing to time-dependent sperm transfer, as redback males transfer the majority of
their sperm within the first 5 min of copulation. This suggests that the link between copulation duration and paternity may instead
be owing to cryptic female choice or the transfer of nongametic ejaculatory substances. Results further indicate that the act of
cannibalism itself might play a role in mediating sperm transfer. This study highlights the importance of understanding mechanisms
of sperm transfer when attempting to interpret the outcome of sperm competition studies. Key words: copulation duration,
Latrodectus hasselti, redback spider, sexual cannibalism, sperm competition, sperm transfer. [Behav Ecol 15:785792 (2004)]
Sperm competition, defined by Parker (1970) as competi-

  

Source: Andrade, Maydianne C.B. - Department of Biological Sciences, University of Toronto at Scarborough
Lovejoy, Nathan - Department of Biological Sciences, University of Toronto at Scarborough

 

Collections: Biology and Medicine; Environmental Sciences and Ecology