title: Strategic ejaculation in simultaneously hermaphroditic land snails: more sperm into virgin mates.
abstract: BACKGROUND
  It has been theorised that sperm competition promotes the strategic usage of costly sperm. Although sperm competition is thought to be an important driving force of reproductive traits in simultaneous hermaphrodites as well as in species with separate sexes, empirical studies on strategic ejaculation in simultaneous hermaphrodites are scarce.
  
  
  RESULTS
  In the present study, we tested whether the simultaneously hermaphroditic land snail Euhadra quaesita adjusts the number of sperm donated according to the condition of the mate and whether the pattern of strategic ejaculation is in line with previously suggested theories. We found that individuals donated much more sperm when they copulated with a virgin mate than when they copulated with a non-virgin.
  
  
  CONCLUSIONS
  The virgin-biased pattern of ejaculation matches the theoretical prediction and suggests that sperm competition significantly influence the reproductive traits of simultaneously hermaphroditic land snails.
authors.affiliation: Department of Environmental Life Sciences, Graduate School of Life Sciences, Tohoku University, Kawauchi 41, Aoba-ku, Sendai 980-8576, Japan. k.kimura.000@gmail.com.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Kimura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Chiba
mesh_terms: D000818:Animals; D003307:Copulation; D012734:Disorders of Sex Development; D005260:Female; D008297:Male; D012726:Sexual Behavior, Animal; D012908:Snails / Q000502:physiology*; D013094:Spermatozoa