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Keywords:

  • Cryptic female choice;
  • odonata;
  • sperm ejection;
  • stored sperm reduction

Abstract.  The few odonate studies of sperm use suggest that females spend apparently more sperm than appears necessary during oviposition (sometimes females may have their sperm stores reduced to 50% after a single oviposition episode). Furthermore, some studies document that females eject sperm during and after copulation. This raises the question of whether sperm reduction may be interpreted as a cryptic female choice mechanism. Using two zygopterans, Ischnura denticollis Burmeister and Enallagma praevarum Hagen, and one anisopteran, Pantala flavescens Fabricius, it is shown that females mate more than once, show a marked reduction in stored sperm, and that this is by ejection of sperm before to oviposition. The extent of sperm reduction is inversely related to the number of eggs laid. When mated to the same male, females show similar reductions in sperm stores and egg load and only rarely does the vaginal duct contain sperm. This suggests that marked sperm reduction is common in this insect order and is not explained by an excess of sperm obstructing the egg passage. It is suggested that female's sperm shortage is better explained as a cryptic female choice mechanism aimed at favouring the sperm of some males. This study provides exciting research avenues for future studies of female choice in an animal taxa whose sexual biology is otherwise regarded as controlled by males.