Natural variability and response interpretation of fecundity, vertebrate-like sex-steroid levels and energy status in the New Zealand mudsnail Potamopyrgus antipodarum (Gray)

► Steroid levels were correlated to fecundity variations in a wild mudsnail population. ► Energy reserves composition and variation were described and linked to fecundity. ► Physiological ranges of variation were defined. ► Data suggest that literature values for fecundity in mudsnails need to be reevaluated. ► Recommendations were drawn for further experiments.