Demography and feeding behavior of Stenostomum leucops (Dugés, 1828)

Freshwater turbellarians, despite their mainly benthic habits, interact with pelagic communities of rotifers and cladocerans. However, very little is known about their demographic characteristics, food preference and functional response. To fill that gap we studied one of the most widely spread species, Stenostomum leucops.  We conducted population growth experiments using abundant food (several rotifer and cladocerans species). To evaluate possible impact of S. leucops on planktonic communities, we conducted prey preference experiments at two temperatures: 18 and 23°C. The number of rotifers and cladocerans consumed was calculated by the difference between the initial and final density. We found that diets supplemented with fresh algae achieved higher S. leucops densities than those with detritus supplements in their diets. In the case of animal diets, Euchlanis dilatata allowed S. leucops reach higher densities than the other zooplankton species; E. dilatata was positively selected for in the selectivity study at both 18 and 23°C.  Stenostomum leucops showed a type II functional response on rotifers and the cladoceran Alona glabra. Our results suggest that S. leucops select their prey according to their vulnerability using different mechanisms, which optimize their food intake.