The crustaceans of the genus Aegla Leach, 1820 are found in streams, rivers and lakes from Franca, São Paulo, Brazil (20º60'S, 47º40'W), to Ilha Madre de Dios, Chile (50º01'10"S, 75º18'45"W) in South America. The growth and cheliped asymmetry of Aegla platensis Schmitt, 1942 were analyzed. The animals were collected from July 1997 to September 1998 at Arroio do Mineiro, Taquara, Rio Grande do Sul, Brazil (29º46'S, 50º53"W). The sex, length, width of the carapace and the total weight of the crab were registered. And after that, the animals were returned to the stream. In the statistical analysis von Bertalanffy's model was used. The growth curves in length (mm) of males and females are described, respectively, by the following equations: L1 = 17.39 [1 - e -0041(t + 3913)] and L1 = 19.12 [1 - e -0.0033 (t + 50.38)]. The equations that describe the growth in weight (g) of males and females, respectively, are: Wt = 2.48 [1 - e -0.0041(t + 3913)]3.04 and Wt - 3.38 [1 - e - 0033(t + 50.38)]3.05 Among 36,5% males had larger left chelae and 52% of females had chelae of the same size.
Crustacea; Decapoda; Aegla platensis; growth