Lack of Host Reproductive Trade-offs Associated with Fecundity Compensation Response to Parasitic Castration

Host-parasite coevolution may result in life-history changes in hosts that can limit the detrimental effects of parasitism. Fecundity compensation is one such life-history response, occurring when hosts increase their current reproductive output to make up for expected losses in future reproduction due to parasitic infection. However, the potential trade-offs between quantity and quality of offspring produced during fecundity compensation are relatively unexplored. This study uses the trematode, Schistosoma mansoni, and its snail intermediate host, Biomphalaria glabrata, to better understand the impacts of this host life-history response. Measures of host reproductive output as well as offspring hatching success and survival were collected to assess the reproductive consequences of infection. Infected snails exhibited fecundity compensation (increase in the number of eggs laid compared to controls) and had a higher probability of laying any eggs at all. Infection status did not play a significant role in hatching or offspring survival to maturity. However, the age of the parental snail had a significant impact on hatching success, as offspring from older parents demonstrated a higher hatching success rate. Overall, the lack of an apparent trade-off between quantity and quality of offspring suggests that infected parental snails invest more resources towards reproduction in order to maintain the fitness of their offspring, possibly at the expense of their own longevity.