• Hermaphrodite;
  • reproductive output;
  • sex allocation;
  • sperm competition


  • 1
    Sex allocation theory predicts that when resources are limited in simultaneous hermaphrodites, the allocation to one sexual function will automatically reduce the resources available to the other function. This study examines the effect of nutritional stress on mating behaviour and male and female reproductive output (dry mass and nitrogen contents of spermatophores, sperm delivered and eggs deposited) in individuals of the simultaneously hermaphroditic land snail Arianta arbustorum kept under three different food regimes: ample (100%), restricted (50%) and extremely restricted (25%) food supply.
  • 2
    Independent of the extent of nutritional stress, 10–12% of the resources taken up were invested in reproductive output (both gender functions together) and 88–90% in maintenance (including faeces and excretion).
  • 3
    Courtship and copulation behaviour was affected by nutritional stress. Snails with an extremely restricted food supply did not mate, except one pair. Individuals with restricted food supply tended to court longer, and copulated for a shorter period, than individuals with ample food supply.
  • 4
    Nutritional stress did not affect the number of sperm delivered. However, snails with a restricted food supply produced fewer eggs. Thus, snails kept under nutritional stress invested relatively more resources in the male function than in the female function. Nevertheless, the absolute reproductive output remained highly female biased (>95% in all experimental groups).
  • 5
    At the individual level, the existence of a trade-off between resources invested in the male vs the female function could not be confirmed. However, there was a trade-off between nitrogen allocated to reproductive function and maintenance in snails with a restricted food supply.