Spermatophore size in bushcrickets: comparative evidence for nuptial gifts as a sperm protection device

Abstract

Male bushcrickets provide females with a nuptial gift, a spermatophylax, which is transferred to females at mating along with the sperm-containing ampulla. Analysis of comparative data of 28 species of bushcrickets (Orthoptera: Tettigoniidae), reveals that male spermatophore size (spermatophylax and ampulla weight) is positively correlated with female refractory period, which, in turn, correlates with male fertilization success. Gift size (the spermatophylax) covaries with ejaculate size (the ampulla), consistent with the hypothesis that it serve as a sperm protection device. There is no significant correlation between any measure of female fecundity and male spermatophylax size, ie variation in spermatophore size among bushcrickets is better explained by a mating-effort function than a paternal investment function. -from Author