Life history of two aquatic insects in the Cacín stream (SE Spain): leuctra geniculata (Plecoptera) and Serratella ignita (Ephemeroptera).

Abstract

The life history, nymphal feeding and secondary production of the mayfly Serratella ignita (Poda 1761) and the stonefly Leuctra geniculata (Stephens, 1836) are studied. Both species are univoltine and complete their nymphal development in the same time (seven months), but L. geniculata growth is constant, while nymphs of first stages of S. ignita do not almost grow during the first months after hatching. Nymphs of both species feed mainly on detritus, but also incorporate other trophic resources to their diet, as diatoms, fungi and coarse particulate organic matter. Some ontogenetic shifts are detected in both species. The annual secondary production is very low for L. geniculata, and it has also low values of cohort production/biomass ratio. In the case of S. ignita, due to the low number of individuals collected, it was not possible to evaluate it.