Maternal effect on salinity tolerance in newborn guppy Poecilia reticulata

Salinity tolerance was examined in 14 strains of the guppy Poecilia reticulata. Salinity tolerance was measured as LD sub(50) 24 h after transfer to serial concentrations of salinity. The LD sub(50) showed high values at birth and significantly decreased within 5 days after birth. The LD sub(50) was higher at birth than at 10 days after birth and at an adult stage in all of the strains. Strain differences were observed in the LD sub(50) at birth, 10 days after birth, and at an adult stage. Positive correlation was not observed between the strain differences at birth and at the adult stage but was observed between 10 days after birth and at the adult stage, suggesting that genetic control for salinity tolerance at birth differs from that of specimens over 10 days after birth. Cross experiments revealed that survival rates of F sub(1) hybrids in 35 ppt seawater at birth showed a positive correlation with rates of female parents but not with male parents. This indicated a maternal effect on salinity tolerance of newborn guppies at birth. The results of backcross suggested that the salinity tolerance of newborn guppies is not controlled by cytoplasmic genetic factors but by the mother's genotypes .