Prey preference of Stenostomum cf. virginianum Nuttycombe, 1931 (Platyhelminthes); a case study in the littoral zone of a tropical reservoir

Abstract

In aquatic systems, littoral zones provide heterogeneous environments where turbellarians can reach densities of up to 40,000 ind. m−2 . To reach such high densities turbellarians need to feed on a variety of prey items. Very little information is available on the feeding ecology of Stenostomum spp. in natural conditions. The objective of this work was to determine the food preference of Stenostomum virginianum based on the density and physical characteristics of prey present in the littoral zone of the Benito Juárez reservoir (Mexico) associated with the macrophyte Egeria densa by analyzing the gut content of the turbellarians. We found that 58% of turbellarians contained rotifers in their gut. The thickness of rotifer lorica did not limit the selection, but the size and availability of the species did. The preferred rotifer prey included Trichocerca porcellus, Lecane closterocerca and Colurella obtusa. This work demonstrates that turbellarians feed on rotifers but are often overlooked in freshwater trophic analyses. They need be considered together with other invertebrate predators such as Asplanchna and cyclopoid copepods because of their impact on rotifer communities in tropical and temperate water bodies.