A demographic study of the life cycle of Tisbe furcata (Baird, 1837) (Copepoda: Harpacticoida)

Abstract

The life-cycle of the harpacticoid copepod Tisbe furcata (Baird, 1837) at 18 C was studied quantitatively. Stage durations were determined by two different methods, using synchronous cohorts. Combined nauplius stages last for 80·4 h; the successive copepodite stages take 23·0, 23·2, 28·0 (♀) to 23·2 (♂), 33·4 (♀) to 24·2 (♂) and 48·8 (♀) to 34·7 (♂) h, respectively. Females develop more slowly but more synchronously than males. Age-specific survival and fertility rates were used to calculate the stable stage distribution in an exponentially growing population. From life-table data the following demographic parameters were computed: intrinsic rate of natural increase rm = 0·233 day−1; net reproductive rate Ro = 94; minimum generation time Tmin = 14·9 days; parameters related to ‘generation time’: T = 19·5 days, = 16·4 days, Tc = 25·4 days.