Bolbophorus damnificus is a digenetic trematode causing economic losses in commercial catfish production. The trematode is transmitted by two different snail species commonly found in commercial catfish ponds, Planorbella trivolvis and Biomphalaria havanensis. Controlling the snail host is the most common management strategy for reducing trematode infections. However, little is known about the population dynamics of the two species.
We performed a 21-week study to evaluate how mate availability influences snail reproduction rates. Three scenarios were tested to investigate egg production and viability when provided available mates continuously (“continuous”), cyclically (“cyclic”), or at a single timepoint (“loner”). Both snails are hermaphroditic and can self-fertilize, though there is a preference for out-crossing. Snail eggs were collected weekly from each treatment, and the total number of eggs (viable and non-viable) and clutches were counted.
Over 93,000 eggs were collected and counted over 21 weeks. Egg production patterns differed between species. B. havanensis produced more eggs per day at the start of the study but declined sharply over the course of the sampling period. Non-viable eggs began to increase near the end of the study, particularly in “loner” treatment, suggesting a depletion in stored sperm. Additionally, B. havanensis showed a dramatically higher mortality rate compared to P. trivolvis.
The data collected from this study sheds new light on mechanisms that may help snails inhabit and persist in new ponds. This also provides an initial estimate of replacement rates in commercial ponds throughout production. Basic biological information on each snail species can aid in developing more targeted management strategies for farmers.