Original Article

Heredity (1995) 74, 654–660; doi:10.1038/hdy.1995.89

Female fitness is increased by frequent mating in grasshoppers

M C Pardo1, M D López-León1, G M Hewitt2 and J P M Camacho1

  1. 1Departemento de Genética, Universidad de Granada, 18071 Granada, Spain
  2. 2School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK

Correspondence: J P M Camacho, Departemento de Genética, Universidad de Granada, 18071 Granada, Spain

Received 13 September 1994.

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Abstract

Radiolabelling experiments with Eyprepocnemis plorans demonstrated that males transfer protein-aceous substances with the ejaculate that are subsequently incorporated into the eggs that the females lay. The amount of male radioactive nutrients detected in the eggs was positively correlated to mating frequency, and the proportion incorporated was almost twice that of egg weight relative to female weight. This might suggest the existence of a specific mechanism selectively incorporating male ejaculate nutrients into the eggs. Another series of experiments with four types of female differing in mating frequency and male availability demonstrated that female production of eggs and embryos is directly proportional to mating frequency. This improvement in female fecundity is from the ejaculate nutrient transfer and both effects are directly dependent on mating frequency. Furthermore, in females crossed sequentially with two different males, there was a significant increase in mating frequency when the female was given the second male. This could be due to an increased mating effort of the second male to displace paternity of the previous male. The low paternity confidence and the polygynandric mating system that characterize E. plorans suggest that male ejaculate nutrients most likely function as a kind of mating effort rather than paternal investment.

Keywords:

ejaculate nutrient transfer, fecundity, mating effort, multiple mating, parental investment, sperm competition

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