Chronic responses of different clones of Daphnia longispina (field and ephippia) to different food levels

Resting eggs are a fundamental reproductive strategy among freshwater cladocerans. Under adverse environmental conditions, whole Daphnia populations can disappear from a lake and a new community will arise from ephippial eggs. Since these new populations are subjected to genetic variation, their responses to environmental stress or contaminants can be different from the "original" population. In the present study. life history responses (reproduction and growth) of Daphnia longispina to different food concentrations was studied. Two Daphnia populations were tested: (a) field clones and (b) ephippial clones. Food (Selenastrum capricornutum) concentration was the stressor tested (absence of food, and low to high food concentrations). The results showed that reproductive responses of D. longispina to the tested food concentrations varied among clones, independently from their origin. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.