Strategic ejaculation and level of polyandry in Callosobruchus chinensis (Coleoptera: Bruchidae)

Takashi Yamane, Takahisa Miyatake

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Variation in the level of polyandry of females produces a difference in the risk of sperm competition among males. As a consequence, investment in ejaculate expenditure by males should vary. We compared the number of sperm ejaculated by males into the female reproductive organ of six strains of the adzuki bean beetle, Callosobruchus chinensis (Coleoptera: Bruchidae), when males were reared at different larval densities in a bean. A significant positive correlation was found between the remating frequency of females and the ratio of the ejaculate sizes of high-density and low-density males as a measure of the response to the risk of sperm competition among males. The measure was estimated by dividing the number of sperm ejaculated by males reared at high larval density in a bean with the number of sperm ejaculated by males reared alone. The number of sperm transferred by a male to a female was not correlated with the duration of copulation. The results suggest an evolutionary relationship between ejaculatory expenditure and the level of polyandry in C. chinensis.

Original languageEnglish
Pages (from-to)225-231
Number of pages7
JournalJournal of Ethology
Volume26
Issue number2
DOIs
Publication statusPublished - May 1 2008

Keywords

  • Adzuki bean beetle
  • Differential allocation
  • Larval density
  • Sperm competition

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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