DEVELOPMENTAL RATES OF THE COPEPODS CALANUS-AUSTRALIS AND CALANOIDES-CARINATUS IN THE LABORATORY, WITH DISCUSSION OF METHODS USED FOR CALCULATION OF DEVELOPMENT TIME

The copepods Calanus australis and Calanoides carinatus developed from egg to adult in 20.3 and 18.3 days respectively at 15.5°C and 16.0 and 12.0 days at 19.5°C. For both species the duration of the first two naupliar stages was short, <1 day. The third naupliar stage was prolonged in C.australis but short in C. carinatus. Isochronal development was approximated from fourth nauplius through third copepodite; fourth and fifth copepodite stages were relatively long. Only female C.australis were produced; 60% of the C.carinatus were female. Equiproportional development was found for C.carinatus but not for C.australis. For both species the variance in stage duration was established at the third nauplius then remained unchanged through the older stages. In calculating developmental rates several commonly used methods were compared. The method of 'first appearance of an individual of a given stage' and 'mean time of appearance of a stage' both yielded estimates of development time that were 10-15% faster than the more commonly used method of 'median development time'. We suggest that all future work on developmental rates of copepods should use a standardized method for the calculation of stage-specific developmental rates and that 'median development time' be the method of choice. © 1990 Oxford University Press.