Condition-dependent spermatophore size is correlated with male's age in a bushcricket (Orthoptera: Phaneropteridae)

During mating, male bushcrickets transfer a spermatophore that consists of a sperm-containing ampulla and a product of the accessory glands, the spermatophylax, which females directly ingest. In the present study, we demonstrate male spermatophore allocation in the bushcricket Poecilimon zimmeri. Males of this species show condition-dependent spermatophore investment. This investment depended upon the age at first mating of males, with older individuals transferring larger spermatophores than younger ones of the same body mass. Independently of age, heavier males transfer larger spermatophores, but the size of males (as measured by femur length) was not a good predictor. Heavier males allocate a lower proportion of their mass to spermatophores and reach their maximal investment point earlier than less heavy males. Spermatophylax production levelled off to a species specific maximum earlier than that of sperm investment (measured as ampulla mass), suggesting that males face high levels of sperm competition. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 354–360.