Spermatophore characteristics in bushcrickets vary with parasitism and remating interval

Male bushcrickets provide females with a nuptial gift, a spermatophore, whi ch is transferred to females at mating. The spermatophore consists of a gel atinous mass, the spermatophylax, and the sperm-containing ampulla. Male sp ermatophore size is positively correlated with insemination rate and female refractory period and therefore with male reproductive success. In this st udy, we examined spermatophylax weight, ampulla weight and sperm number in males of Poecilimon mariannae parasitized by the acoustically orienting fly Therobia leonidei. We show that in parasitized males, spermatophylax weigh t decreases with the level of parasitism. In line with the hypothesis that parasitism is a cost to reproduction, we found that spermatophylax weight w as reduced at remating. In contrast, the replenishment of the spermatophyla x in unparasitized males was complete after 2 days and was increased no fur ther after 3 days. Both sperm number and ampulla weight showed an increase over time since last mating and sperm production was estimated at a constan t rate of 500,000 per day in all individuals, regardless of parasitism. The allocation of investment in components of the spermatophore varies greatly with parasitism and remating. Both factors had rather independent effects on spermatophore constitution, revealing functional constraints acting on s permatophore characteristics in bushcrickets, which are important for under standing the selection pressures working on its components.