Sperm competition in the water strider, Gerris remigis
1989
Rubenstein, D.I.
Sperm competition occurs in the giant water strider. In serial mating experiments using normal and sterilized males, the last male to mate was able to displace, on average, 65% of the sperm of the previous male. Success of second males was, however, highly variable but can be partially explained by relative copulation lengths of the two males. Although there was a tendency for long copulations by the first male to be followed by long copulations by the second, second males could only obtain the 'last male' advantage if their copulations were long relative to those of first males. A long latency period occurred between genital contact and the effective transfer of sperm as no viable eggs were produced until copulations lasted at least 15 min. Once sperm transfer began, however, virtually the entire sperm load was delivered instantaneously to the female. Females continued to lay fertile eggs for 24 days after a single copulation, and although this period increased to 30 days after two matings, the difference was not statistically significant. Although the incompleteness of sperm displacement suggests that alternative copulatory strategies among males should be common, the existence of a long latency period before sperm transfer should not only reduce this tendency, but also increase female choosiness.
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