Spermatophore characteristics in bushcrickets vary with parasitism and remating interval |
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Authors: | G U C Lehman A W Lehmann |
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Institution: | Department of Zoology II, University Erlangen-Nürnberg, Staudtstra?e 5, 91058 Erlangen, Germany, DE
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Abstract: | Male bushcrickets provide females with a nuptial gift, a spermatophore, which is transferred to females at mating. The spermatophore
consists of a gelatinous mass, the spermatophylax, and the sperm-containing ampulla. Male spermatophore size is positively
correlated with insemination rate and female refractory period and therefore with male reproductive success. In this study,
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 weight decreases with the level of parasitism. In line with the hypothesis
that parasitism is a cost to reproduction, we found that spermatophylax weight was reduced at remating. In contrast, the replenishment
of the spermatophylax in unparasitized males was complete after 2 days and was increased no further after 3 days. Both sperm
number and ampulla weight showed an increase over time since last mating and sperm production was estimated at a constant
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 spermatophore characteristics in bushcrickets, which are important for understanding the
selection pressures working on its components.
Received: 13 September 1999 / Received in revised form: 4 February 2000 / Accepted: 13 March 2000 |
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Keywords: | Spermatophylax Sperm competition Host-parasitoid relationship Ormiini Orthoptera |
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