Methane carbon supports aquatic food webs to the fish level.

Large amounts of the greenhouse gas methane (CH(4)) are produced by anaerobic mineralization of organic matter in lakes. In spite of extensive freshwater CH(4) emissions, most of the CH(4) is typically oxidized by methane oxidizing bacteria (MOB) before it can reach the lake surface and be emitted to the atmosphere. In turn, it has been shown that the CH(4)-derived biomass of MOB can provide the energy and carbon for zooplankton and macroinvertebrates. In this study, we demonstrate the presence of specific fatty acids synthesized by MOB in fish tissues having low carbon stable isotope ratios. Fish species, zooplankton, macroinvertebrates and the water hyacinth Eichhornia crassipes were collected from a shallow lake in Brazil and analyzed for fatty acids (FA) and carbon stable isotope ratios (δ(13)C). The fatty acids 16:1ω8c, 16:1ω8t, 16:1ω6c, 16:1ω5t, 18:1ω8c and 18:1ω8t were used as signature for MOB. The δ(13)C ratios varied from -27.7‰ to -42.0‰ and the contribution of MOB FA ranged from 0.05% to 0.84% of total FA. Organisms with higher total content of MOB FAs presented lower δ(13)C values (i.e. they were more depleted in (13)C), while organisms with lower content of MOB signature FAs showed higher δ(13)C values. An UPGMA cluster analysis was carried out to distinguish grouping of organisms in relation to their MOB FA contents. This combination of stable isotope and fatty acid tracers provides new evidence that assimilation of methane-derived carbon can be an important carbon source for the whole aquatic food web, up to the fish level.

New species of Tanytarsus van der Wulp (Diptera: Chironomidae) from São Paulo State, Brazil.

Tanytarsus lenyae sp. n., T. giovannii sp. n., T. fittkaui sp. n. and T. alfredoi sp. n. from São Paulo State (Brazil) are described and diagnosed, the first as adult male and pupa, and the remaining as male, pupa and larva. The species were collected in areas of Cerrado, at the boundaries of São Carlos city. Complete diagnoses and drawings of the species are given. The imagos can be separated from other species of Tanytarsus van der Wulp mainly by differences in the antennal ratio, dorsomedian extension of the eyes, the thorax and wing setation, the shape of anal tergal bands, the anal point armament and the shape of superior volsella, digitus and median volsella. The pupae are characterized by the thoracic horn armament, the arrangement of the precorneals, the shape of anal comb and the abdominal setation. The larvae can be separated by differences in the antennal pedestal, the sclerotization of the second antennal segment, the size of Lauterborn organ pedicels, the shape of the clypeal seta S3 and the sclerotization of the mentum. Apparently, the four new species are not closely related, and the anal point armament alone would be enough to separate one species from the other.

New species of Tanytarsus van der Wulp (Diptera: Chironomidae) from São Paulo state, Brazil

Tanytarsus lenyae sp. n., T. giovannii sp. n., T. fittkaui sp. n. and T. alfredoi sp. n. from São Paulo State (Brazil) are described and diagnosed, the first as adult male and pupa, and the remaining as male, pupa and larva. The species were collected in areas of Cerrado, at the boundaries of São Carlos city. Complete diagnoses and drawings of the species are given. The imagos can be separated from other species of Tanytarsus van der Wulp mainly by differences in the antennal ratio, dorsomedian extension of the eyes, the thorax and wing setation, the shape of anal tergal bands, the anal point armament and the shape of superior volsella, digitus and median volsella. The pupae are characterized by the thoracic horn armament, the arrangement of the precorneals, the shape of anal comb and the abdominal setation. The larvae can be separated by differences in the antennal pedestal, the sclerotization of the second antennal segment, the size of Lauterborn organ pedicels, the shape of the clypeal seta S3 and the sclerotization of the mentum. Apparently, the four new species are not closely related, and the anal point armament alone would be enough to separate one species from the other.

Larvas de Chironomidae ( Diptera) em depósitos de folhiço submerso em um riacho de primeira ordem da Mata Atlântica (Rio de Janeiro, Brasil) / Chironomidae larvae (Diptera) in submerged litter accumulations in a first order stream of the Atlantic Forest (Rio de Janeiro, Brazil)

Neste estudo investigamos a fauna de larvas de Chironomidae presente em depósitos submersos de matéria orgânica (folhiço) em um riacho de primeira ordem na região serrana (cerca de 1100 m) do Estado do Rio de Janeiro. A fauna de Chironomidae do folhiço submerso foi quantitativamente amostrada durante o outono, inverno, primavera e verão. A fragmentação do folhiço foi estimada e a presença de folhas, madeira, raízes e frutos foi investigada. Foram estudadas variações na composição da fauna e na estrutura do folhiço entre as estações do ano e levantadas hipóteses acerca de possíveis fatores que influenciariam os quironomídeos nestes depósitos de folhiço. As subfamílias Chironominae, Orthocladiinae e Tanypodinae foram encontradas e as participações de freqüência de cada subfamília e gênero calculadas em cada estação. Chironominae e Orthocladiinae foram identificados até o nível genérico, e 23 gêneros foram encontrados. Lauterborniella, Polypedilum e Tanytarsus foram os gêneros mais abundantes. Foi observada uma variação na estrutura do folhiço submerso entre as estações do ano, sendo provavelmente influenciada pelas interações entre fatores climáticos (principalmente precipitações) e o relevo e seus efeitos na bacia de drenagem. A fauna de Chironomidae também apresentou mudanças durante o período estudado, com grupos variando quanto à participação relativa e quanto à ocorrência entre as estações. Os efeitos do clima na vegetação e nas características físicas do riacho foram discutidos para elucidar suas influências nos depósitos de folhiço e na fauna de Chironomidae.

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.