No abstract

No abstract

Rotifer production in a shallow artificial lake (Lobo-Broa Reservoir) was studied for twenty consecutive days between August 25, 1995 and September 13, 1995, during the dry season. Two species were dominant, during this period namely Filinia pejleri and Keratella americana, contributing, respectively, 36% and 28% to total rotifer numbers. Production estimates of these species were, respectively, 41.93 and 80.70 micrograms dry weight.m-3.d-1, corresponding to 18.45 and 35.51 micrograms Cm-3.d-1. The population of F. pejleri was numerically more abundant than that of K. americana, while the production of the former was less, as a result of lower egg to female ratios.

ABSTRACT.A new species of gall midge, Lopesia eichhorniae sp. nov. (Cecidomyiidae, Diptera), associated with rhizomes of Eichhornia azurea (Sw.) Kunth (Pontederiaceae) is described. This is the first record of Lopesia galls in this species of macrophyte, quite common in natural and artificial lakes in Southeast Brazil. Illustrations of the adults (male and female), pupa, larva, and gall of the new species are presented.

The lack of knowledge about freshwater biodiversity in remote areas like montane Andean rivers is noticeable and hinder the development of efficient conservation plans for aquatic ecosystems. Habitat requirements of tropical Andean fishes have been poorly analysed, despite the relevance of these ecological features on the fish conservation strategies. The present study aimed to examine fish assemblages along the altitudinal gradient in tropical Andean rivers and their relationship to habitat features to detect the most relevant abiotic factors and their implication on conservation. This study was conducted on a regional scale, along six basins located in tropical Andes (500 to 2,692 m a.s.l.). We studied fish diversity and distribution and their habitats along these elevation gradients. We found 6,320 specimens from 53 genera. Our analysis for the six most common and widely distributed genera (Astroblepus, Brycon, Bryconamericus, Chaetostoma, Pimelodella and Trichomycterus) underlines the relevance of hydromorphological variables on fish community structure in the Andean montane rivers, whereas human alterations seem to be less significant. These findings could be useful for current management and conservation strategies considering present threats over tropical montane rivers.