Sperm competition in Ischnura elegans (Vander Linden) (Zygoptera: Coenagrionidae)
Odonatologica , Volume 16 - Issue 2 p. 201- 207
The capture, preservation and subsequent examination at known times during copulation has shown that most mature females copulate more than once. By marking copulating pairs it was found that some females accepted second males on the same day. Copulations of decapitated males with intact females were relatively short-lasting as also was the case when both sexes had been decapitated. However, copulations of intact males with decapitated females were long-lasting and resembled those of undisturbed pairs. Males therefore apparently control the duration of copulation. Measurements of sperm volumes in copulating females support the hypothesis that copulating males remove all the sperm of rivals from the bursa, but none from the spermatheca. Sperm vesicles of males contain a mean of 0.011 ± 0.0019 mm3( n=14) during stage 1 of copulation. Spermathecae of females after sperm transfer contain a mean of 0.0064 ± 0.0023 mm3 (n=I I), whereas bursae contain a mean of 0.0023 ± 0.0009 mm3 (n=14). During stage II of copulation, males transfer the whole vesicle contents, which is about 5 times the volume that can be accommodated in the bursa. This apparent anomaly is discussed.
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