During copulation, C. haemorrhoidalis S S displace the sperm of rivals stored by the 2. During displacement, sperm stored in 2 spermathecae are ejected by the 2 as a consequence of S genitalic stimulation: the aedeagus distorts 2 vaginal plates in which mechanoreceptive sensilla are embedded. The sensilla control spermathecal sperm release and a wider aedeagus displaces more sperm. There is variation between 9 2 in their sensillum number which might also affect sperm displacement rate. The role of sensillum number and aedeagal width in sperm displacement variation in copulations whose duration was controlled was investigated. Results indicated that only aedeagal width could predict sperm displacement variation. The neural communication between the vaginal plates and both spermathecae was also examined. Previous observations suggested a “lateral” control of sperm ejection between each vaginal plate and its corresponding spermatheca. This was corroborated by stimulating the mechanoreceptive sensilla of 2 2 that underwent different surgical treatments: only those 2 9 whose vaginal plate nerves were cut, showed no volumetric decline in sperm in the corresponding spermatheca. Finally, the effect of copula duration (number of aedeagal copulatory movements) on sperm ejection was experimentally examined. In natural conditions, $ 6 perform approximately 50 aedeagal movements during copulation. There was no difference in sperm volumes between the pairs of 2 2 that were subjected to 50 and 80 aedeagal movements of stimulation using the same aedeagus. These results help to understand the nature of the spermathecal sperm displacement mechanism in this sp.


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Societas Internationalis Odonatologica

A. Córdoba-Aguilar, & M.T. Siva-Jothy. (2004). Sperm displacement ability in Calopteryx haemorrhoidalis (Vander Linden): male and female roles, male limits in performance, and female neural control (Zygoptera: Calopterygidae). Odonatologica, 33(3), 245–252.