Influence of abiotic and biotic factors on morphological variation of Keratella cochlearis (Gosse) in a small Andean lake

Morphological variation of Keratella cochlearis was studied during a spring -summer period in a small Andean lake. Morphometry was studied in relation to temperature, food resources, cladoceran competitors and invertebrate pre dators. Three different morphs were recorded. We observed lack of allometri c growth of the posterior spine. Absence of allometric growth could be rela ted with the low density of a predaceous water mite and the small size of t he cladocerans present in the lake. Fluctuations in lorica length and width were negatively correlated with temperature and algal biovolume. We discus s the benefits of this morphological response of Keratella in relation to e nvironmental conditions.