Spermatophore allocation strategy over successive matings in the bushcricketIsophya sikorai(Orthoptera Phaneropterinae)

Abstract

During mating, male bushcrickets transfer edible spermatophores that consist of a large sperm-free spermatophylax and a sperm-containing ampulla. The effect of consecutive matings on nuptial gift and sperm numbers in the bushcricket Isophya sikorai was examined. Males and females differed in body weight and mating history influenced their weight. Males differed in spermatophore weight, as well as the weights of spermatophylax and ampulla. Spermatophore (spermatophylax + ampulla) and spermatophylax weight of I. sikorai increased with male body weight, but not with ampulla weight. Male age had a significant effect on sperm number, with older males producing more sperm. Female weight but not mating number of female had a significant effect on spermatophore weight. Males increased the size of the spermatophylax and sperm number when presented with larger females, but they did not adjust their ampulla weight. Male age affected spermatophylax weight when mating with heavier females. Males reached their maximal absolute sperm number point at about middle age of their mating period due to an age-dependent shift in covariation between the ampulla and spermatophylax weight and ampulla size increases over a longer period. We conclude that production of a spermatophore and its components is costly, therefore males should strategically adjust their spermatophore components among mating opportunities. Female quality is an important predictor in searching males, and those males transfer significantly larger spermatophore and ejaculates to higher quality (heavier) females. Briefly, this study suggest that male I. sikorai strategically allocate spermatophore size and sperm number with respect to various factors such as his age, sperm competition and female size in a multiple mating system.

Mating Behavior and Spermatophore Characteristics in Two Closely Related Bushcricket Species of the Genus Phonochorion (Orthoptera: Phaneropterinae)

“…This was supported in a study using 33 species within the genus Poecilimon in the barbitistine bushcrickets (McCartney et al 2008) and by another study in a related genus, Isophya (I. sikorai: Uma and Sevgili 2015). Although a correlation has been found between body size and sperm number for some species, there is no relationship for other species (Vahed and Gilbert 1996;McCartney et al 2008).…”

“…In this analysis, we included a random effect (male identity) and fixed-covariate effects (male mating number, male age, male body weight, female body weight and ampulla weight). The basis for including the latter effects was that males Vahed and Gilbert 1996 can make adjustments in their spermatophore components in relation to eclosion (age as days) and body conditions and mating status (Lehmann and Lehmann 2009;Uma and Sevgili 2015). There was no correlation between male body size (measured as pronotum length and hind femur length) and spermatophore and its contents (Pearson Correlation, p>0.05) in either species.…”

“…In the present study, although the male weight was useful predictor and affected the spermatophore and ampulla weights for both species, male mating number had an interaction with spermatophore weight and ampulla weight for only P. uvarovi. Spermatophore weight has been widely shown to be related to body weight Wedell and Arak 1989;Heller and Reinhold 1994;Uma and Sevgili 2015) because body weight is a sex-linked trait and is closely associated with the spermatophore weight (Reinhold 1994) or, alternatively, can be a result of pleiotropy (Fedorka and Mousseau 2002). When body weights were compared, it was seen that P. artvinensis was larger than P. uvarovi, and accordingly their average of spermatophore, spermatophylax and ampulla weights were higher, but their relative weights were not significantly different.…”

“…For example, there are few studies on the genus Isophya, which has more than 90 species in the Palearctic region and is the second largest genus after the genus Poecilimon, which contains about 150 species (see Can 1959;Sevgili 2004;Eades et al 2014;Uma and Sevgili 2015). The genus Phonochorion is a little known group and only three species are described for the genus belonging to the barbitistine bushcrickets, representing a total of 15 genera in the world (Sevgili et al 2010;Eades et al 2014).…”

“…Of the bushcrickets, the tribe Barbitistini species have been intensively examined in terms of mating behaviors and spermatophore investment strategies (e.g., Heller and Reinhold 1994;Vahed 1995;Sevgili and Reinhold 2007;McCartney et al 2008;Lehmann and Lehmann 2009;Uma and Sevgili 2015). Typical mating behavior of the bushcrickets has been described by several authors (Gwynne 2001;Lehmann and Lehmann 2009).…”