Occurence of intersexuality in a laboratory culture of the copepod Eurytemora affinis from the Seine estuary (France)

We show in this study that intersexuality can occur in the estuarine copepod Eurytemora affinis, and we reported the presence of three intersexual copepod individuals from a laboratory culture of this species from the Seine estuary conducted at low temperature (7A degrees C). These individuals presented both female and male characteristics. The prosome size and antennules of intersex individuals were similar to those of normal females, but all the other morphological details were more similar to normal males. The appearance of the three intersex individuals in the culture at low temperature coincided with a decrease in food quality due to a feeding with Rhodomonas marina at its stationary phase. This induced a significant decrease in the mean clutch size and skewed sex-ratio in favor of males. The reduction in food quality in addition to low temperature of 7A degrees C (which induced slow development) is suspected to be responsible of the appearance of intersex individuals. This stressful situation seems to propagate to the following two generations at low temperature in contrast to the case of the experiment at higher temperature 20A degrees C where no intersex individual was observed. These results confirmed the role of food quality in sex determination of copepods. Moreover, the role of early developmental stages and also the consequences of stressful conditions throughout different generations were discussed.