The size at the onset of morphological sexual maturity (SOM) of the anomuran crab Aegla platensis Schmitt, 1942 was estimated through the changes in the ratios of corporal dimensions of the animals. For this, aeglids were monthly collected, from July 2007 to June 2008 in Lajeado Bonito (27º25'27''S, 53º24'39''W), a first order tributary of the rio da Várzea, in Frederico Westphalen municipality, state of Rio Grande do Sul, Brazil. Samples of 437 males and 368 females were used, with cephalothorax length (CC) ranging from 6.00 mm to 31.75 mm in males and from 6.08 mm to 27.92 mm in females. The following corporal dimensions of collected individuals were measured: cephalothoracic length, abdomen width (LA), length of the right propodus cheliped (CPD), length of the left propodus cheliped (CPE). After the register of these measures, the crabs were returned to the stream, to the same places where they were collected. Estimation of the size at the onset of morphological maturity was performed using the Mature 2 software. The most appropriated relations for this analysis in males were CPD x CC (SOM: CC=18.2 mm) and CPE x CC (SOM: CC=20.1 mm) and for females LA x CC (SOM: CC=16.5 mm).
Allometry; puberal molting; intraspecific variability
