Heritability estimates for ammonia resistance and growth-related traits in the razor clam Sinonovacula constricta

The razor clam Sinonovacula constricta, one of most important mariculture bivalve species in China, suffered from the variable challenges such as ammonia stress, drastic salinity fluctuation, highly variable temperature. Ammonia stress represents a common stressor and now considered to be the main limiting factor in intensive culture systems of S. constricta, a potential strategy for the challenge is selecting strain that are genetically resistant to the ammonia stress. Here, we constructed full-sib families and performed two challenge experiments in different life stages to estimate genetic parameters of ammonia tolerance and growth traits in S. constricta. A total of 45 families including 26 families at 5-month-old and 19 families at 10-month-old were used to test the ammonia tolerance, as well as the growth-related traits (Shell length, Shell height, Shell width and Body weight) of individuals. The heritability estimates of the two experiments were similar and comparable, moderate estimates were observed for heritability of ammonia tolerance (0.20 +/- 0.07-0.28 +/- 0.04), while moderate to high heritability (0.36 +/- 0.13-0.64 +/- 0.37) were found for growth-related traits. Slightly low genetic (0.34 +/- 0.32-0.42 +/- 0.30) and phenotypic (0.01 +/- 0.05-0.15 +/- 0.04) correlations were detected between ammonia tolerance and growth traits in the early life style, while the correlations were also low in genetic (0.13 +/- 0.29-0.39 +/- 0.25) and in phenotypic (0.03 +/- 0.04-0.13 +/- 0.04) in the later life style. These findings confirm the existence of genetic variation for ammonia tolerance and growth traits and provide important information to guide effective selection of S. constricta.