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.

Em embriões de Macrobrachium olfersi (Wiegman, 1836) foram analisadas as características morfológicas bem como o dia do desenvolvimento em que estas características surgiram. Machos e fêmeas de M. olfersi foram coletados na Ilha de Santa Catarina e colocados em aquários de água doce, na temperatura de 26°C e ciclo escuro e claro de 10:14 horas. Fêmeas ovígeras foram monitoradas diariamente para retirada de uma amostra de 20 ovos da câmara incubadora. O desenvolvimento embrionário foi caracterizado através do sistema de estagiamento diário. Embriões vivos e fixados foram analisados (48x) em intervalos de 24 horas (dia embrionário). O índice do olho foi calculado em cada dia embrionário, a partir do aparecimento da pigmentação no olho. O desenvolvimento de M. olfersi foi caracterizado em 14 dias embrionários (E), onde entre E1 a E4 ocorreu a clivagem, gastrulação, disco germinativo e organização do nauplius embrionizado. Nos dias subseqüentes foi caracterizado o crescimento do nauplius embrionizado bem como a formação e encurvamento do pós-nauplius. Em E7 observou-se a pigmentação no olho, seguida do início dos batimentos cardíacos em E8. Entre E9 e E14, ocorreu de forma mais intensa o processo de organogênese, principalmente dos sistemas nervoso, cardiovascular e digestivo. O estagiamento diário do desenvolvimento de M. olfersi permitiu o reconhecimento de diferentes formas embrionárias, bem como de ritmos de crescimento e diferenciação do embrião, os quais são essenciais à formação gradual do plano do corpo.

Morphological landmarks of Macrobrachium olfersi embryos were examined and their appearance times were related to each embryonic day. Males and females of M. olfersi (Wiegman, 1836) were captured in Santa Catarina Island and kept in freshwater small tanks at 26ºC and 10:14 dark: light cycle. Ovigerous females were monitored daily to remove samples of 20 eggs from brood pouch. The embryonic development was characterized through daily staging system. Living and fixed embryos were analyzed (48x) in intervals of 24 hours (embryonic day). The eye index was calculated in each embryonic day from the appearance of the eye pigmentation. The development of M. olfersi was described in 14 embryonic days (E), where the cleavage, gastrulation, germinal disk and egg nauplius are developed from E1 to E4. The subsequent days were characterized by the growth of the egg nauplius, as well by the formation and the bent of the post-nauplius. At E7, the eye pigmentation appeared and was followed by the beginning of heartbeats at E8. From E9 to E14, more intensive organogenesis processes occurred, mainly on the nervous, cardiac and digestive systems. The daily staging of development of M. olfersi development enabled the recognition of different embryonic forms, as well as growth and differentiation rhythms of embryo, which were fundamental to the gradual formation of the body plan.

Foi estudado o desenvolvimento embrionário de quatro espécies de Palaemonidae em condições controladas de laboratório. Adultos de Macrobrachium olfersi (Wiegman, 1836), Macrobrachium potiuna (Müller, 1880), Palaemon pandaliformis (Stimpson, 1871) e Palaemonetes argentinus (Nobili, 1901) foram coletados na Ilha de Santa Catarina, SC, Brasil e mantidos à temperatura de 26ºC. Foram analisadas as seguintes características embrionárias: forma do ovo, organização do vitelo e planos de clivagem, apêndices naupliares e pós-naupliares, estomodeo, lobos ópticos, olhos, telson, curvatura do embrião e o espaço ocupado pelo embrião no ovo. Diferentes ritmos de desenvolvimento foram observados espécies, sendo que M. potiuna mostrou o maior tempo de embriogênese. As espécies seguem o padrão de embriogênese de ovos centrolécitos, sendo identificadas características similares do desenvolvimento, possibilitando o estabelecimento de oito estágios embrionários, comuns as quatro espécies.

The embryonic development of four species of the family Palaemonidae was studied under laboratory conditions. Adults of Macrobrachium olfersi (Wiegman, 1836), Macrobrachium potiuna (Müller, 1880), Palaemon pandaliformis (Stimpson, 1871) and Palaemonetes argentinus (Nobili, 1901) were collected in Santa Catarina Island, Santa Catarina, Brazil and maintained at 26ºC. The following embryonic characters were analyzed: egg shape, yolk organization and cleavage plane, naupliar and post-naupliar appendages, stomodeum, optical lobes, eyes, telson, embryo curvature and the space occupied by the embryo in the egg. Different rates of development were observed for the four species, with M. potiuna showing the longest time of embryogenesis. The species studied followed the pattern of embryogenesis of centrolecithal eggs, enabling the identification of similar features of the development, and the establishment of eight common embryonic stages.

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.