Effects of temperature, feeding and acridine on reproduction of the calanoid copepod, Diaptomus clavipes Schacht

Abstract

Chronic toxicity determinations (using changes in reproduction as an index of toxicant stress) were performed on adults of the freshwater calanoid copepod, Diaptomus clavipes, at temperatures of 16, 21 and 26°C. Adults were paired and then exposed for 15 days to five concentrations (0·32-3·2 mg litre −1) of the azaarene, acridine, in a renewal system. Two control groups (methanol control and well water control) were also used. Four reproductive criteria (number of eggs per clutch, number of clutches per female per day, number of eggs per female per day and percentage egg hatch) were evaluated. Mean clutch size was significantly reduced in acridine-exposed animals only at 21°C. Rate of clutch production was a more sensitive indicator of acridine stress than clutch size at all temperature tested. Rate of egg production yielded results similar to those for clutch size. Egg viability was not affected by either temperature or acridine concentration, with more than 84% of the eggs hatching in most cases. No reproduction occurred at the highest acridine concentration tested (3·2 mg litre −1) at all three temperatures; copepods at the next highest acridine concentration (1·8 mg litre −1 produced only 2·5% of the total 1127 clutches produced in all exposure conditions.