BENTHONIC INSECTS IN EL TALA RIVER: THEIR COMMUNITY STRUCTURE BASED ON A LONGITUDINAL GRADIENT

COLLA, MARIA FLORENCIA; SALAS, LILIANA; SILVERIO REYES, MARÍA JUANA

Tafí de Valle, Tucumán

Jornada; XXVI Jornadas Científicas de la Asociación de Biología de Tucumán.; 2009

Asociación de Biología de Tucumán

The aim of this work is to determine the structure of the benthonic entomofauna of El Tala River (Catamarca, Argentine) and its longitudinal variation. Five sampling stations were established along the river. In situ it was determined: altitude, latitude and longitude; dry stream-bed wide; wet stream-bed wide; river depth; river current speed; water and air temperature. Benthonic insects were collected during the dry season, using a square parcel sampler with a 0,09 m2 surface and 300µm net opening. Samples were fixed in situ with 96º alcohol. Insects were identificated to their Family taxon in the laboratory. Density, faunistic richness and diversity exhibited longitudinal variation. Sampling station II was the most abundant. From sampling station I to III a decreasing trend in the numbers of orders and families was observed, whereas sampling stations IV and V showed an increasing trend. Sampling station V showed the highest Family richness (17), the highest value of Shannon index (2,74) and the lowest value of Simpson´s dominance index (D=0,22). Sorenson´s quantitative index indicated that sampling stations I and V were the most similar (76%). Variations found could be attributed to the interaction of water´s physical and chemical variables, environmental variables and anthropic factors.