COMPOSICIÓN DE LA DIETA DE Asplanchna girodi (PLOIMA, ASPLANCHNIDAE) EN UN EMBALSE ALTOANDINO ECUATORIAL EN COLOMBIA BASADO EN OBSERVACIONES DE CAMPO

Abstract

Asplanchna girodi (de Guerne, 1888) is a predatory rotifer of wide distribution in temperate and tropical freshwater ecosystems. Of this species, little is known about its diet and its food preferences under natural conditions, since most of the work related to this aspect has been carried out under laboratory conditions. During a short monitoring program at La García Reservoir, a high Andean equatorial reservoir located in the central region of the department of Antioquia (Colombia), in which this species reached a total density of 2.296,2 ind.L-1, studied the composition of the A. girodi diet based only on the direct observation, under the microscope, of the organisms contained in the stomachs of all the individuals present in the simples. Between June and September 2014, integrated samples composed of five depths were taken monthly at three monitoring stations in the entire water column, with a sampling bottle of 10 L capacity. The collected material was filtered through a 30µm plankton net of mesh eye. It was found that A. girodi, presented a wide trophic preference that included the foraging of a dinoflagellate (Ceratium, Schrank), five species of rotifers and a cladoceran. These results lead to the conclusion that A. girodi is possibly an opportunistic species, since consumption is directed at the species with the highest availability (in this case Ceratium) and with the greatest energy savings, since no investment is made in the search for specific prey and in turn would become an important factor in controlling phytoplankton populations.