Abstract:
Several species of the copepod genus Acartia are shown from existing data to complete each molt-to-molt phase of the life cycle in a constant time period. This molting pattern is termed isochronal development. Increase in mass at each stage is a nearly constant fraction of the weight at the beginning of the stage (with the exception of the late naupliar stages). Coupled with isochronal development this implies that growth in Acartia is exponential in time through most of the life cycle. Under isochronal development a proportionately shorter part of the total development is spent in the copepodite stages than in forms with stages of progressively greater duration. This may be a response to preference of the predators of Acartia for the older stages or a general adaptation leading to a shorter life cycle and higher rates of population increase.
