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Georgina Bond-Buckup 2 ABSTRACT. Population's dynamics of Aeg/a p/atensis Schmitt (Crustacea, Decapoda, Aeglidae). The crustaceans of the genus Aeg/a Leach, 1820, are found in streams, rivers of caves, current rivers and lagoons, from Franca, São Paulo, Brazil (20 0 60'S, 47°40'W), to Ilha Madre de Dios (50°01 ' IO"S, 75°18'45"W), Chile in South America. The crabs (Aeg/a p/atensis Schmitt, 1942) were monthly sampled by hand fromjuly 1997 to september 1998 in Arroio do Mineiro, Taquara (29°46'S, 50 0 53'W), Rio Grande do Sul, Brazil. The sex, lhe length and width of lhe carapace were registered. After being collected lhe animaIs were returned to the stream. The reproductive period, the size at the first maturation and lhe sex-ratio were identified. The reproductive period of A. p/atensis lasts lhe whole year. The percentage of ovigerous females is higher in july. The size at the first maturation is from 14,40 to 15,60 mm of carapace lenglh. The sex-ratio is 1,08 male to 1 female. The annual population 's density is 12 animais per square meter. KEY WORDS. Crustacea, Aeg/a p/atensis, reproduction and population dynamics Os aeglídeos são um grupo de crustáceos peculiares por serem os únicos anomuros de águas continentais, sendo encontrados somente na América do Sul, ocorrem em arroios, rios de correnteza e lagos desde o município de Franca, São Paulo, Brasil, até a ilha Madre de Dios, no Chile (BOND-BuCKUP & BUCKUP 1994). Fazem parte da cadeia alimentar dos ambientes límnicos, sendo considerados importantes na dieta de rãs, peixes e aves (ARENAS 1974), alimentando-se de larvas de insetos simulídeos (MAGNI & PY-DANIEL 1989). Aspectos da reprodução e do crescimento de Aegla laevis laveis (Latreille, 1818) foram abordados por BAHAMONDE & LOPEZ (1961) no Chile, onde verificaram o período reprodutivo, o tamanho da primeira maturação e a proporção de machos por fêmeas. No Brasil, LOPEZ (1965) estudou a reprodução de Aegla odebrechtti paulensis Schmitt, 1942 (hoje A. paulensis) em São Paulo. JARA (1977) fez algumas observações sobre a biologia de Aegla rostrata Jara, 1977, no Chile. RODRIGUES & HEBLING (1978) estudaram aspectos biológicQS e biométricos de Aeglaperobae Hebling & Rodrigues, 1977, em São Paulo. Diante dos escassos trabalhos sobre a dinâmica populacional do grupo, o presente estudo trata dos aspectos bio-ecológicos de Aegla platensis Schmitt, 1942, em especial o período reprodutivo e o tamanho da população em ambiente natural.

Benthic macroinvertebrate in four rivers, three in the Pelotas River basin (Divisa, Marco and Silveira rivers, in the headwaters of the Uruguai River) and one in the Taquari-Antas system (Antas River), a tributary in the Guaíba basin, in the state of Rio Grande do Sul, were identified. Two samples were collected in summer, autumn and spring, with one replicate in each river. The total of 28,961 specimens included members of Platyhelminthes, Annelida, Acarina, Insecta, Crustacea and Mollusca. The Silveira and Marco rivers showed significant differences in the indices of Shannon-Weaver (H’), Simpson’s Reciprocal (1/D), Margalef (DMg) and Equitability (E). The Silveira River showed the highest means of diversity and the EPT index (Ephemeroptera, Plecoptera, Trichoptera). Comparison among the diversity indices, considered individually, were insufficient to show differences in community structure, for the purpose of ecological characterization of the rivers. The EPT values characterized the Divisa River as having the highest abundance (73%), followed by the Marco (71%), Antas (48%) and Silveira (36%). These results suggest that the Silveira River is subject to moderate environmental stress, from human impact, although it showed the highest diversity of the major macrobenthic groups.

Crustaceans are exposed to many environmental variables that follow annual and daily cycles differing with geographical region, and which cause behavioural, feeding and metabolic alterations. Study of intermediate metabolism in crustaceans has shown high inter-and intra-specific variability, which makes it difficult to determine a standard metabolic profile. This variability can occur because of several factors such as habitat, stage in the moult cycle, sexual maturity (especially in females), feeding state, food at hand and seasonality, since these factors determine differential metabolic response. Glucose is the principal monosaccharide present in the haemolymph of crustaceans and it serves six main purposes: synthesis of mucopolysaccharides, synthesis of chitin, synthesis of ribose and nicotinamide adenine dinucleotide phosphate reduced (NADPH), the formation of pyruvate, and the synthesis of glycogen (Hochachka et al., 1970; Chang and O'Connor, 1983; Herreid and Full, 1988). The main glycogen reserves in crustaceans are the muscle, the hepatopancreas, the branchiae and the haemocytes. The storage place of this polysaccharide varies according to the species (Johnston and Davies, 1972; Herreid and Full, 1988). The absence of a central glycogen deposit seems to be an adaptation of several classes of animals to changes in environmental factors (Hochachka et al., 1970). The stored glycogen is utilized in molting, adaptation to hypoxia and/or anoxia, osmoregulation, growth, in the different stages of reproduction, and during fasting periods (Hu,