Body mass index does not decline during winter for the sedentary marine gastropod Crepidula fornicata

Extremes in environmental conditions can limit growth and reproduction of animals. Sedentary marine animals are particularly susceptible to winter food limitation since they cannot relocate to more favorable conditions. Winter conditions have been linked to tissue mass declines as high as 70% in several temperate-zone suspension-feeding bivalve species; however, no comparable studies have been conducted on intertidal gastropods. Here, we investigate whether the suspension-feeding intertidal marine gastropod Crepidula fornicata also loses substantial tissue mass during the winter. We calculated body mass index (BMI; mg dry weight/(cm shell length)3) for individuals collected at different times of year for seven years from 2009-2019 and determined whether winter or environmental conditions influenced BMI. Remarkably, C. fornicata body mass did not decline during winter months; indeed, a relatively poorer body condition was associated with higher seawater temperature, higher air temperature and higher chlorophyll concentration. In a laboratory experiment, we found that C. fornicata that were starved for three weeks at 6 °C (local winter seawater temperature) showed no detectable declines in BMI compared to field collected individuals. Future studies should document energy budgets of sedentary marine animals at low winter seawater temperatures, and the impact of short-term elevated temperatures on those energy budgets.