ROLES OF RESOURCE AND PARTNER AVAILABILITY IN SEX DETERMINATION IN A PARASITIC COPEPOD

Because sexuality plays an essential role in gene transmission and con sequently in the evolution of species, investment into male or female function constitutes a key factor in tbe:reproductive success of indiv iduals. Environmental sex determination permits adaptive sex choice un der unpredictable environmental conditions, where the environment:affe cts sex-specific fitness, and where offspring can predict their likely adult status by monitoring an appropriate environmental.cue. The para sitic copepod Pachypygus gibber dis,lays three sexual-phenotypes (i.e. one female and two kinds of male) which are environmentally determine d (i.e. after conception and in response to environmental cues). Here, we report an experimental analysis on the combined action, during lar val development, of availability of food.resources and sexual partners in the sex determination of this species.