The metabolic responses of two crayfish species living in different habitats, Parastacusdefossus and Parastacus brasiliensis, were analyzed after different periods of hypoxia (2.0mg O(2)/L of oxygen). In the laboratory, groups of animals were subjected to hypoxia for 1, 2, 4, and 8h. The hemolymph, hepatopancreas, muscle, and anterior and posterior gills were removed for determination of glucose, free glucose, glycogen, lactate, total proteins, total lipids, total cholesterol, arginine, and arginine phosphate. In both species, glucose and lactate increased significantly after 4h of hypoxia, but decreased after 8h (p>0.05) from the beginning of the experiment. Reductions of glycogen, lipids, and cholesterol were recorded in hepatopancreas and muscle tissue, especially of P. defossus, after 4h of hypoxia. Free glucose levels decreased in all tissues of P. brasiliensis, mainly in the hepatopancreas and muscle (p<0.05), while P. defossus showed smaller reductions of these reserves. All reserves in the anterior and posterior gills, with exception of the glycogen reserves, behaved similarly in both species. Both crayfishes stored and used arginine phosphate, mainly P. defossus, which also showed higher concentrations of all metabolites than did P. brasiliensis. Both species showed metabolic adaptations to hypoxia, but, as expected, P. defossus appeared to be better adapted.

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Abstract. Freshwater crayfishes of the genus Parastacus are intersex, i.e., show characteristics of both sexes in the same individual; also, intersexuality has been documented in hermaphroditic species. The aim of this study was to analyze the gonads of Parastacus varicosus, characterizing its sexual pattern. The animals were collected at Cova do Touro, Gravataí, Rio Grande do Sul, Brazil. Three sexual forms were identified: intersex females, intersex males, and transitional specimens showing an ovotestes gonad that could only be identified by means of histological analysis. All specimens had two pairs of gonopores and gonoducts. The oviduct had a wider diameter in females, whereas in males the vasa deferentia were more developed. Gonads were composed of two parallel structures located in the cephalothorax. Female gonads were classified into three stages. The presence of transitional specimens may indicate that sex change occurs, with protandric hermaphroditism, as observed in other species of Parastacus. Because previous studies had demonstrated that P. varicosus is a gonochoristic species in a population from Uruguay, the present study addressed the possibility that the sexual pattern depends on differences in environmental factors among populations. To improve understanding of evolution of hermaphroditism in these crustaceans, their reproductive dynamics should be studied, including identification of the factors stimulating male and female functions.

O crescimento de Aegla longirostri Bond-Buckup & Buckup, 1994 foi analisado mensalmente de setembro de 1996 a agosto de 1997 no Rio Ibicuí-Mirim, Itaára, localidade de Val-de-Serra, Estado do Rio Grande do Sul, Brasil. O sexo dos espécimes coletados foi registrado e a medida do comprimento do cefalotórax foi tomada com um paquímetro. O crescimento foi estimado usando o modelo de von Bertalanffy. As curvas de crescimento em comprimento do cefalotórax (mm) de machos e fêmeas foram descritas, respectivamente, pelas equações: Ct = 27,9 [1 - e - 0,0069 (t + 24,78)] e Ct = 21,45 [1 - e - 0,0048 (t + 45,62)]. A idade máxima estimada para machos foi de um ano e nove meses e para fêmeas dois anos.

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