The effect of temperature on herbivory by the omnivorous ectotherm snail Lymnaea stagnalis

Rising temperatures likely affect the trophic interactions in temperate regions as global warming progresses. An open question is how a temperature rise may affect consumer pressure and plant abundance in shallow aquatic ecosystems, where most consumers are omnivorous. Interestingly, herbivory (plant-eating) is more prevalent toward low latitudes in ectotherms such as fish and aquatic invertebrates, and this may be temperature driven. We used pond snails ( Lymnaea stagnalis L.) as a model aquatic ectotherm species and tested their consumption of both animal prey ( Gammarus pulex L.) and plant material ( Potamogeton lucens L.) at three different temperatures (15, 20, and 25°C). Higher temperatures led to higher consumption rates by the omnivore on both plant food and animal prey when fed separately. When the food was offered simultaneously, the pond snails consistently preferred animal prey over plant material at all tested temperatures. However, the omnivore did consume plant material even though they had enough animal prey available to them. Based on our experiments, we conclude that with increasing temperatures, L. stagnalis will only increase their consumption rates but not change food preference. Further studies are needed to test the generality of our findings across aquatic species to predict the effect of warming on aquatic plant consumption.