Growth analysis of Daphnia early juvenile stages as an alternative method to test the chronic effect of chemicals

It is recognized that the mature size and clutch size of the cladoceran Daphnia are strongly affected by the size at birth and growth rate during the early juvenile stages. Individuals at the neonatal stage are most sensitive to environmental stress such as toxic chemicals, and therefore such stress may indirectly control the reproductivity of Daphnia by directly affecting the growth of neonates. These facts suggest that growth rate during the juvenile stages would be a good indicator of the effect of toxic chemicals on Daphniaʹs reproduction, which is the parameter usually determined in chronic toxicity tests. In the present paper, I propose a new short-term test that involved analysis of Daphnia growth at the early juvenile stages.