Angela M. Sanseverino

Larvas de Chironomidae ( Diptera) em depósitos de folhiço submerso em um riacho de primeira ordem da Mata Atlântica (Rio de Janeiro, Brasil)

We investigated the fauna of larval Chironomidae in accumulations of submerged organic matter (litter) in a first-order stream in the mountain region (about 1000 m a.s.l.) of Rio de Janeiro state. The Chironomidae fauna of submerged litter was quantitatively sampled during autumn, winter, spring and summer. Litter fragmentation was estimated and the presence of leaves, wood, roots and fruits was investigated. Variations in the chironomid fauna composition and litter structure were studied, and hypotheses about factors influencing chironomid in these litter accumulations were proposed. The subfamilies Chironominae, Orthocladiinae and Tanypodinae were present and frequency participation of each subfamily and genus was calculated for each season. The Chironominae and Orthocladiinae were identified to genus level, and a total of 23 genera were found. Lauterborniella, Polypedilum and Tanytarsus were the most abundant genera. We observed a variation in the submerged litter structure among seasons, which is probably influenced by geological and climatic factors (mainly precipitation) affecting the drainage basin. The structure of the chironomid fauna changed during the studied period, with genera varying in participation and occurrence among the four seasons. Climatic effects on riparian vegetation and on stream physical characteristics were discussed in order to elucidate their influence on submerged litter accumulations and the chironomid fauna structure.

First record of symphoresy between nymphs of the stonefly Kempnyia tijucana, and chironomid larvae, Nanocladius (Plecopteracoluthus) sp., in the Neotropics.

The symphoretic relationship between a species of Nanocladius (Plecopteracoluthus) (Diptera, Chironomidae) and Kempnyia tijucana (Plecoptera, Perlidae) is recorded and described for the first time from southeastern Brazil. About 31% of the collected perlids were hosts of the chironomid larvae. The entire larval cycle of N. (Plecopteracoluthus) sp. may be completed on a single instar of K. tijucana and the larval position on the host varied according to the stage of development of the chironomid, apparently being constant for young and old instars.

Structure and dynamics of chironomid fauna from a sand dune marsh in rio de Janeiro state, Brazil

The benthic fauna of a sand‐dune marsh in a restinga environment was monthly sampled from January, 1987, to February, 1988, using a 0.4 mm mesh width benthos collector apparatus. An amount of 43484 chironomid larvae were collected, corresponding to 15.2% from the total of the invertebrate benthic fauna sampled. The average densities were 3180.70 ± 2641.41 ind./m2 for frequency, and 0.0737 ± 0.0691 g/m2 for iomass. The following genera were found: Ablabesmyia, Clinotanypus, Coelotanypus, Labrundinia, Larsia (?), Monopelopia, Procladius, Chironomus, Goeldichironomus, Nimbocera, Polypedilum and Zavreliella. Concerning feeding habits, gut content analysis showed that the species are generalists, feeding on any available source. Product moment correlation was performed to verify associations between the taxa and environmental factors. Water level variation and the macrophyte life cycles are the main directive factors on chironomid populational fluctuations.