Brood sex ratio in the apple snail Pomacea canaliculata (Gastropoda : Ampullariidae) is determined genetically and not by environmental factors

摘要

remains unclear. This study investigated the effects of various environmental factors on brood sex ratios, rearing hatchlings from the same egg masses (or parents) under two different conditions for each environmental factor. The factors investigated were: (1) presence of adult males or females; (2) food availability; (3) position in the egg mass (upper or lower part); (4) temperature (20 or 25 degreesC); (5) age of the parents; (6) size of the aquarium; and (7) indoor or outdoor conditions. None of these factors had a significant effect on the brood sex ratio. On the other hand, brood sex ratios were significantly different among different egg masses or parents in all experiments. These results suggest that environmental sex determination does not occur in this snail. Instead, both the sex determination and sex ratio variation are under genetic influence.