Dry vs. Rainy: the seasonal response of freshwater snails in artificial reservoirs of semiarid

Our research aimed to investigate the seasonal distribution of freshwater gastropods, specifically Biomphalaria straminea and Melanoides tuberculata, collected from water supply reservoirs in a semi-arid region of Brazil. Our hypothesis was that the abundances of these species would exhibit seasonal variation influenced by environmental factors such as temperature and water levels throughout the dry and rainy seasons.
During the study, from 2017 to 2020, we collected 5,555 individuals of Biomphalaria straminea and 67,122 individuals of Melanoides tuberculata. Captured using standardised techniques, the data include both species abundance and age classes (juveniles and adults).
Our results revealed a significant seasonal distribution for Biomphalaria straminea, with higher abundances observed during the dry season. In contrast, Melanoides tuberculata showed stable populations throughout the study, with no significant correlation with environmental variables. Temperature and seasonal changes had a greater influence on the abundances of Biomphalaria straminea compared to Melanoides tuberculata.
These findings support our hypotheses regarding the reproductive strategies of these species. Biomphalaria straminea, known for self-fertilisation, exhibited a higher proportion of juveniles concentrated during the dry season. On the other hand, Melanoides tuberculata, which reproduces through parthenogenesis, maintained stable populations regardless of environmental conditions.