Taxonomia, bionomia e estrutura da comunidade de larvas de megaloptera (insecta) em igarapés nos estados do Amazonas e Roraima, Brasil

Abstract

The taxonomy, bionomy and the community structure of Megaloptera larvae associated with physical-chemical and environmental factors were studied in Amazonas and Roraima states, Brazil. A total of 120 streams were sampled between April and December 2006. Additional samples were taken ibetween September 2005 and December 2007. Two Megaloptera families were sampled during the study: Corydalidae with two genera (Corydalus and Chloronia), seven species (Corydalus affinis, Corydalus batesii, Corydalus ignotus, Corydalus flavicornis, Corydalus nubilus, Corydalus sp. n. and Chloronia hieroglyphica) and two morphotypes (Corydalus sp. 1, Corydalus sp. 2). Sialide was represented by only one species (Protosialis flammata). Last-instar larvae of C. contrerasi sp. n., C. affinis and C. flavicornis were described; the last two of these species were registered for the first time in Roraima and in Brazil, respectively. The number of Megaloptera species for Roraima state increased to seven, for Brazil to 20 and for the Neotropical Region to 64. A key was developed to identify last-instar Megaloptera larvae to family, genus and species/morphotype levels based on specimens collected in the study area. In the laboratory, the period of time for embryological development of C. nubilus was approximately two weeks, similar to the periods for species in the Neartic Region. Larvae of Corydalus, Chloronia and Protosialis, with body sizes similar to the sizes of adults collected in the study area were maintained under laboratory conditions for a maximum of 332, 180 and 86 days, respectively, until adult emergence. For these same genera, the endurance times of the pre-pupae were 7, 7 and 5 days, respectively and, for the pupal stage, the times were 14, 10 and 5 days, respectively. Larvae of Cantharidae (Coleoptera) and Chloropidae (Diptera) were observed preying on Corydalus spp. eggs. The sexual behavior of C. affinis is described for the first time. Richness and abundance of Megaloptera larvae were higher in streams sampled in Amazonas state than in Roraima; community composition also was different in these two states. Although some species were related to abiotic factors we measured, the majority were generalists.occuring in varied environmental conditions. Anthropogenic impact (deforestation) did not have an effect on the Megaloptera community. The results of the present study provide an example of the importance of integration between taxonomic and bio-ecological studies, especially for organisms that inhabit aquatic ecosystems, in which taxonomy is still incipient throughout the world.