Effects of the Mother's Environmental Salinity on Seawater Tolerance of Newborn Guppy Poecilia reticulata

Effects of the mother's environmental salinity on seawater tolerance of the offspring were exam ined in the guppy.Seawater tolerance of newborn guppies was expressed as a survival rate 24 h after transfer to 35 ppt seawater at birth.Newborn guppies in the seawater-adapted F22-SW(SW) strain showed a higher survival rate in seawater than those in the freshwater-adapted F22 and F22-SW(FW) strains.When gravid females of the seawater-adapted F22-SW(SW) strain yielded their offspring more than 5 days after acclimation to fresh water, the survival rate of the newborn guppies in seawater decreased to a level comparable to that of the freshwater-adapted F22 and F22-SW(FW) strains.On the other hand, when gravid females of the freshwater-adapted F22 strain yielded their offspring after accli mation to seawater, survival rates of their newborn guppies in seawater increased and most of them were able to survive in seawater.These results indicate that the mother's environmental salinity en hances the seawater tolerance of the offspring and contributes to successful reproduction of the guppy in seawater.