Sperm numbers, sperm storage duration and fertility limitation in the Odonata

Abstract

The status of the Odonata as a model taxon for studying the evolution and diversity of reproductive behaviours is shown here to have declined relative to crickets and Drosophila. Very few available data on ejaculate size, the number of sperm stored by females and the duration of sperm storage reveal poor knowledge of these areas in the Odonata. Some observations tentatively suggest that species without direct sperm removal transfer larger numbers of sperm. Observations on the fertilization success of eggs laid by sexually isolated females and the temporal variation in paternity were used to assess the longevity of the sperm population in the female. The generality of the claim that female odonates have full fecundity after a single mating can not be upheld. In addition, it is not clear whether any possible decrease in fertilization ability in isolated females is due to decreasing sperm quantity or quality. Costs and benefits of sperm longevity, sperm storage and multiple mating are discussed for both sexes. It is proposed that mating frequency and sperm storage duration may be linked in the Odonata. Testable predictions and ideas related to sperm biology are put forward in which odonates may be used to address general questions of evolutionary biology.

Keywords: Odonata, dragonfly, sperm age, sperm longevity, sperm number

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