ABSTRACT. Anthropic action influence on aquatic macroinvertebrates in streams from a cerrado region of Southwestern of the State of São Paulo, Brazil. The richness and spatial distribution of aquatic macroinvertebrates were studied in streams from a cerrado region, Assis, State of São Paulo, with the purpose of verifying the effect of the anthropic action on the fauna. The collections took place at the headwaters of the Ribeirão Água do Cervo (the main water supplier of the city of Assis). Nine collection stations were established in which ten standardized pebble packages were placed (equivalent volume, 300 cm 3 each). After twenty-five days of exposure, the packages were removed from the stream. The macroinvertebrates associated to each of the pebble packages were removed and identified. The results showed a smaller richness in the most damaged station. There was not significant relation between the physicochemical factors and the fauna. The intensity of anthropic action was significantly related with the fauna. KEYWORDS. Organic pollution, aquatic insects, lotic ecosystems.RESUMO. Foram estudadas a riqueza e a distribuição espacial da fauna de macroinvertebrados aquáticos em riachos da região de cerrado de Assis, SP, com a finalidade de verificar o efeito da ação antrópica sobre a fauna. As coletas foram realizadas em nascentes do Ribeirão Água do Cervo, principal fornecedor de água da cidade de Assis. Foram estabelecidos nove pontos de coleta nos quais foram colocados dez pacotes de seixos de tamanho padronizado (volume equivalente a 300 cm 3 cada). Após 25 dias de exposição, os pacotes foram removidos do riacho. Os macroinvertebrados associados a cada pacote de seixos foram triados e identificados. Os resultados mostraram uma menor riqueza no local mais impactado. Não houve relação significativa entre os fatores físico-químicos e a fauna. No entanto, a ação antrópica foi significativamente relacionada com a fauna. PALAVRAS-CHAVE.Poluição orgânica, insetos aquáticos, ecossistemas lóticos.

-The present study evaluated the relative growth and allometry of Massartella brieni Lestage and Thraulodes sp. (Leptophlebiidae: Ephemeroptera). The morphometric analysis was based on 23 measurements and was conducted using a multivariate approach. Throughout postembryonic ontogeny, all of the head measurements, including those of the mouthparts, exhibited negative allometric growth. The mesothorax and wing pad exhibited positive allometric growth. The hind legs lengths in M. brieni and the fore and hind legs lengths in Thraulodes sp. exhibited positive allometry. The abdominal length in these two species exhibited positive allometric growth. Positive allometry was also observed along the abdomen width for M. brieni, and isometry was observed for Thraulodes sp. The relative strengthening of the thorax (in preparation for the winged stage) and the relative increase in the abdomen (which may be related to the development of the reproductive structures) during growth indicate that many of the structures that exhibit positive allometric growth are related to the transition from the aquatic to the adult stage of development.

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