Demographicparameters of adults of Pseudodiaptomusannandalei (Copepoda: Calanoida): Temperature-salinity and generationeffects
Résumé
The calanoid copepod Pseudodiaptomusannandalei is distributed exclusively in the Indo-Pacific regions from subtropical to tropical estuaries and shallow coastal waters. Its population dynamics is not well understood despite its ecological importance to natural ecosystems and potential applications to aquaculture. We studied the combined effects of temperature and salinity on survivorship and reproduction of P. annandalei. The experimental protocol included adult cohort life table analysis and observations on reproductive parameters of individual females (paired with males) in relation to 9 different temperature-salinity combinations. At salinity level 10-20, the average survival (lx = 0.5) and life expectancy at moulting was significantly higher at 18 °C (38 days); however, at salinity 30, the survival was significantly higher at 25 °C (22.17 days) than either of those at 18 or 32 °C. The gross and net reproductive rates were higher (267 and 176 nauplii female− 1 respectively) at salinity 10 and temperature 25 °C. Neither interclutch duration nor embryonic development time was affected by salinity; whereas, temperature had a significant effect on both parameters. The clutch size was significantly affected by salinity, but not by temperature. Across temperature-salinity combinations tested in the present study, the total lifetime fecundity was significantly correlated with adultgeneration time, but not with longevity. The population growth rate (Euler's r) was negatively related to the adultgeneration time across temperature-salinity levels tested. Continued production of viable fertile clutches by the female required remating with the male at frequent intervals. Our results suggest that the most appropriate temperature-salinity combination for this species is 25 °C at salinities 10-15 for reproduction, and 20 °C at salinity 10 for survival.