The reproductive aspects of the freshwater shrimp Potimirim glabra (Kingsley, 1878) were studied from September 1997 to February 1999. Monthly, samples were collected with sieves, on the river edge, under the edging vegetation or in small pools. At the laboratory, shrimps were sexed and measured in their total lenght, from the tip of the rostrum to the end of telson with precision callipers. The ovigerous shrimps were separated and counted for fecundity determination. The eggs diameter was measured with calibrated stereomicroscope. A total of 3281 shrimps were collected, among which, 47% male, 46% female (13.4% ovigerous females) and 7% young shrimps. The Sex ratio was 1:1. Ovigerous females were present during all seasons, but the reproductive peak occurred in spring. The ovigerous female showed total lenght from 9.5 to 26.0 mm and carapace lenght from 1.6 to 7.3 mm. The mean fecundity was 545 eggs per female, with a minimun of 223 eggs and a maximum of 860 eggs. The first sexual maturation probably occur at 9.5 mm total lenght. The mean diameter of the eggs size was 0.32 mm (minor) and 0.53 mm (major).

The reproductive aspects of the freshwater shrimp Palaemon pandaliformis (Stimpson, 1871) were studied from March, 1998 to February, 1999. Monthly, samples were collected with sives, on the river edge, under the edging vegetation or in small pools. At the laboratory, shrimps were sexed and measured in their total lenght, from the tip of the rostrum to the of telson with precision callipters. The ovigerous shrimps were separated and counted for fecundity determination. The eggs diameter was measured with calibrated stereomicroscope. A total of 872 were collected among which, 46% female, 29% male and 25% juvenil. The sex ratio was 1:1.57. Ovigerous females were present during all seasons, but the reproductive peak accurred in Spring. The ovigerous female showed total lenght from 23.0 to 39.6 mm. The mean fecundity was 137 eggs per female, with a minimum of 40 eggs and a maximum of 270 eggs. The first sexual maturation probably occur at 23.0 mm total lenght. The mean diameter os the eggs size was 0.51 mm (minor) and 0.73 mm (major).