ABSTRACT Macrobrachium olfersii (Wiegmann, 1836) is a prawn that lives in shallow and transparent freshwater in Southern Brazil. Aquatic organisms that inhabit these systems can be exposed to incident UV radiation. Many studies have demonstrated the effects of ultraviolet (UV) radiation on the development, survival rate, morphological abnormalities, and impairments in swimming behavior in crustaceans. However, fewer studies have elucidated how the embryos of crustaceans respond to the exposure of UV radiation. Thus, the aim of this study was to evaluate whether UVA and UVB affect biometrical and morphological parameters of eggs and embryos of M. olfersii. Embryos were divided into two groups: Group I, composed of embryonic day 7 (E7) to E10 and Group II, composed of E11 to E14. Both groups were irradiated with 60 min UVA and 30 min UVB. Non-irradiated embryos at the same stages were used as controls. UVA and UVB radiation induces variations in morphometric parameters, such as egg volume, egg water content, and eye index. UVB radiation also induced an increase of embryonic cell death. We conclude that the embryonic cells of M. olfersii respond differentially to UVA and UVB radiation in accordance with the evaluated parameters.

The aim of this study is to characterize the reproductive features of Macrobrachium olfersii (Wiegman, 1836) from Santa Catarina's lsland. The animals were collected in freshwater streams of the Ratones Hidrografic Basin (site A1) and at the Peri's Pond (site A2). In the laboratory, the procedures of sexual differentiation were carried out to classify the individuais in males, females or ovigerous females, followed by the determination of total weight (g), quelipod relative weight (g) and total length (mm). The eggs were removed from the ovigerous females and counted. Sexual maturity and fecundity were analyzed based in the dimensions and number of eggs carried by ovigerous females. The water temperature on the capture sites varied from 17 to 29ºC throughout the months of study. A total of 503 individuais were captured, with 129 individuais from site A1 and 374 from site A2. The mean total size and length was 49.65 mm and 3.79 g for the males, 38.75 mm and 1.61 g for the females and 36.19 mm and 1.08 g for the ovigerous females. At the sites A1 and A2, the individual sexual maturity was reached with 27.3 and 21.2 mm of total length, respectively, while populational sexual maturity was estimated for the 45.0 to 50.0 mm class at site A1 and for the 30.0 to 35.0 mm class at site A2. The ovigerous females carried an average of 3464 eggs at site A1, and 1440 eggs at site A2. These reproductive features, presented by M. olfersii, show the species' plasticity, which can be associated with environmental variations, contributing to its reproductive success.

Biological aspects of palemonids, collected from March, 91 to December, 95 in the Ratones Hidrographic Basin, Florianópolis, Santa Catarina, have been investigated. Individuals of different sizes of Macrobrachium acanthurus (Weigmann, 1836), Macrobrachium carcinus (Linnaeus, 1758), Macrobrachium olfersii (Weigmann, 1836), Macrobrachium potiuna (Müller, 1880), Palaemonetes argentinus Nobili, 1901 and Palaemon pandaliformis (Stimpson, 1871) were registered. These prawns, showed reproductive strategies, typical of the Palaemonidae (Rafinesque, 1815), associated to species particularities, and seem to adapt to different environmental conditions.

Biometric and reproductive aspects of Palaemon pandaliformis (Stimpson, 1871) from Ratones Mangrove, Florianópolis, Santa Catarina, have been investigated. Individuals were monthly collected from August, 91 to July, 93 and the temperature and salinity registered. Biometry, sex-ratio, sexual maturity, fecundity and reproductive cycle have been determined. The temperature showed defined temporal distribution. This species presents animal reproductive cycle, relatively high individual and populational fecundity, and the ovigerous females were larger than males and other females of the same species.