Diminished food resources are associated with delayed reproduction or increased post-reproductive mortality in brood-bearing terrestrial isopods Armadillidium vulgare Latreille

Female terrestrial isopods (Crustacea: Oniscidea) carry eggs and early instars in a ventral brood pouch. We investigated reproductive expenditure of female Armadillidium vulgare Latreille under the condition of restricted food resources. Regardless of food availability, few cases of spontaneous termination of care were observed and most gravid females either successfully produced offspring or died while still bearing eggs. There were no differences in pre-hatching maternal mortality between food-restricted and non-restricted groups, but females exhibited significantly higher post-reproductive mortality when food availability was heavily reduced after oogenesis. This did not occur when food was restricted prior to oogenesis, but in this case females delayed the onset of reproduction. An association between mortality and past reproduction was further supported by high laboratory mortality, regardless of food availability, in non-gravid females field-captured late in the reproductive season. Maternal investment in A. vulgare thus appears to be energetically expensive. Despite the ability to terminate care, however, females continue to invest heavily in reproduction even when resources are scarce and the likelihood of mortality is high.