The thecamoebae (Protozoa, Rhizopoda) of small Amazonian forest streams and their possible use as indicator organisms for waterquality

Abstract The thecaboemae fauna of seven central amazonian forest streams — among them the stream of the "Bacia Modelo" — was analised. 129 morphotypes are shortly characterized in a "list of morphotypes" with accompanying figures (Plates 1-7); 39 morphotypes were observed alive and food uptake determined in 20 of these. Their food consists primarily of spores and hyphae of fungi which decompose submerged leaf litter and detritus. Analysis of sequential samples suggests that most species were found in each stream, but that collection in further streams is expected to increase the total number of morphotypes considerably. Frequency and distribution of morphotypes, as well as total population density, are characteristic for each stream and seem to reflect water quality and geographic distance between streams. Thecamoebae density is 2-5 times higher in original, un-mixed black water than in crystalline water of similarly low conductivity. Total number of morphotypes is almost invariable between streams (64-76). These results suggest that thecamoebae populations as a whole, and single species in particular, may be suitable indicators for the quality of waters in natural and in distrurbed streams.