Individual effects and interactions of salinity,temperature, and zinc on larval development of the grass shrimp Palaemonetes pugio. I. Survival and developmental duration through metamorphosis

Larvae of the estuarine grass shrimp Palaemonetes pugio (Holthuis) were reared from hatch through successful completion of metamorphosis in 80 combinations of salinity (3 to 31%), temperature (20° to 35°C), and zinc (0.00 to 1.00 ppm Zn⁺⁺). Response-surface methodology was employed to depict the individual effects and interactions of the three factors on survival and developmental duration through total larval development. Outside the optimal salinity-temperature conditions of 17 to 27 S and 20° to 27°C, viability of larvae was reduced by both the individual effects of salinity and temperature and interactions between the two factors. Survival capacity of larvae and resistance adaptations to salinity and temperature were progresively reduced by zinc concentrations from 0.25 to 1.00 ppm Zn⁺⁺. Response-surface analysis of the data suggested that the duration of total larval development of P. pugio was least at salinities from 18 to 23 and at temperatures from 30° to 32°C. At both higher and lower salinity-temperature conditions and in increasing zinc concentrations from 0.25 to 1.00 ppm Zn⁺⁺, developmental rates were retarded. A significant zinc-temperature interaction existed, whereby increasing zinc concentrations reduced both survival and developmental rates of larvae more at suboptimal temperatures. Larval resistance to zinc toxicity was least at supraoptimal salinities, indicative of a significant zinc-salinity interaction. The reduced viability, restricted euryplasticity, and retarded developmental rates of P. pugio larvae developing in media with low-level zinc contamination would limit the distributive properties of the pelagic phase in the life cycle of the species and reduce recruitment both into and out of the parent estuarine population.