Effects of prehatching salinity and initial larval biomass on survival and duration of development in the zoea 1 of the estuarine crab, Chasmagnathus granulata, under nutritional stress

The effects of individual larval biomass, and salinity experienced during embryogenesis (i.e., prehatching salinity) on starvation tolerance and growth of zoea 1 of the estuarine crab (Chasmagnathus granulata) were evaluated in laboratory experiments. Freshly hatched zoeae 1 were obtained from broods maintained at three salinities (15‰, 20‰ and 32‰), and cultured at 20‰ under different initial feeding periods and subsequent food deprivation (“point of reserve saturation” experiment: PRS) or under initial periods of food deprivation and subsequent feeding (point of no return experiment: PNR). Another group of larvae were used for determination of biomass (dry weight, carbon, and nitrogen) of zoea 1.Larval survival and duration of development depended on the length of feeding period: no larvae reached the second instar under complete starvation; survival was higher and duration of development shorter as the feeding period lengthened. After different initial feeding periods (PRS experiment), zoeae 1 that hatched from eggs incubated at the prehatching salinities of 15‰ and 20‰ showed higher survival and shorter duration of development than those at 32‰. Prehatching salinity also affected the amount of reserves accumulated during the first 2 days after hatching, with larvae from 15‰ and 20‰ showing the highest percentage of total accumulation of carbon and nitrogen. Initial larval biomass did not affect survival, but it had a slight effect on duration of development, with larger larvae (in terms of biomass) developing faster. After different initial starvation periods (PNR experiment), prehatching salinity did not affect survival, but it affected duration of development: larvae from 15‰ and 20‰ reached the second instar earlier. Variability in survival and duration of development was explained in part by among-brood variability in initial larval biomass: larvae with higher biomass showed higher survival and shorter duration of development. Thus, C. granulata, survival and duration of development under food stress depend on the interaction between environmental conditions experienced before and after hatching (pre- and posthatching factors, respectively).