Section 8
Chapter 7,946

The wartbiter spermatophore and its effect on female reproductive output orthoptera tettigoniidae decticus verrucivorus

Wedell, N.; Arak, A.

Behavioral Ecology and Sociobiology 24(2): 117-126


ISSN/ISBN: 0340-5443
DOI: 10.1007/bf00299643
Accession: 007945433

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Male wartbiters Decticus verrucivorus transfer elaborate spermatophores to females during copulation. The spermatophore is attached externally to the female's genitalia and consists of two parts: a large, gelatinous, sperm-free portion, the spermatophylax, eaten by the female after mating; and a sperm-containing ampulla, eaten after the spermatophylax has been consumed. Since females taken longer to eat larger spermatophylaxes, the duration of ampulla attachment is positively correlated with spermatophylax size. Two series of experiments were carried out, one in which the size of the spermatophylax consumed by females and the duration of ampulla attachment were manipulated in concert and another in which they were manipulated independently. Some females were also maintained on a protein-free diet and either supplied with or deprived of spermatophylax material. The amount of protein in the diet, but not the amount of spermatophylax material consumed, influenced female longevity, lifetime fecundity, and egg weight. When females were deprived of the spermatophylax, an experimental increase in the duration of ampulla attachment induced longer periods of unreceptivity in females after mating, a more rapid onset of oviposition, and an increased oviposition rate. Consequently, the number of eggs laid by females during their nonreceptive refractory periods increased significantly with increasing duration of ampulla attachment up to 180 min; however, there was no significant increase in the number of eggs laid beyond 180 min of ampulla attachment. This closely corresponds to an ampulla attachment duration of 188 min expected when a male transfers a natural spermatophylax of mean size to the female. These results suggest that the amount of ejaculate transferred to the female, and not the amount of spermatophylax material per se, is the factor controlling female receptivity and oviposition behavior. Since we did not detect any effect of spermatophylax consumption on female fecundity or egg weight, we conclude that the spermatophylax of D. verrucivorus functions primarily as a sperm protection device rather than as a form of male parental investment.

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