ABSTRACT

The effect of bilateral eyestalk ablation on haemolymph osmotic and Na + , Cl-, K , Mg 2 + and Ca 2 + concentrations was investigated in the freshwater shrimp Macrobrachium olfersii during acute exposure (1, 3, 6, 12 and 24 h) to sea-water of 21%o S. Analysis of variance treatment indicated that haemolymph osmotic and Na', Cl-, K , Mg 2 + and Ca 2 + concentrations were affected by exposure time (p < 0.01). However, only [Na + ] was affected by eyestalk ablation (p < 0.01), destalked shrimps exhibiting haemolymph Na+ concentrations approximately 15 to 30% lower than control shrimps. These results are interpreted to indicate that less Na+ enters the haemolymph of eyestalkless shrimps on exposure to seawater of 21%o S, presumably resulting from the absence of an eyestalk-located neurofactor. A factor causing the influx of Na + into the haemolymph is thus proposed to be present in the eyestalk ganglionic system of intact Macrobrachium olfersii in freshwater. Reduction in secretion of the factor may act to reduce Na+ entry in high salt environments.

The economic importance that myticulture is conquering in Santa Catarina State (South of Brazil) explains the crescent search for new coastal sites for farming. Physiological and biochemical studies of the mussel Perna perna are important to the establishment of methodologies for program assessment and environmental monitoring, allowing to infer about site quality and possible influences of xenobiotic agents on coastal areas. In order to evaluate effects caused by lead poisoning (1.21 µmol.L -1 ), the mussels were maintained at constant temperature (25 o C) and fed with Chaetoceros gracilis for 15 days. The control group was acclimatized in sea water 30‰. At the end of this period time, physiological measurements were carried out along with statistic analysis for filtration rates, lead assimilation and overall respiratory activity. The mechanism of multixenobiotic resistance (MXR) was particularly evaluated in standardized gill fragments using rhodamine B accumulation and its quantification under fluorescence optical microscopy. Regarding the control group, results had shown that the mussels maintenance in a lead-poisoned environment caused higher filtration rates (1.04 and 2.3 and L.h -1 .g -1 ; p < 0.05) and lower assimilation rates (71.96% and 54.1%, respectively). Also it was confirmed a lesser rhodamine B accumulation in the assays under influence of lead, suggesting that this metal induces the MXR mechanism expression in mussel P. perna. These results indicate that such physiological and biochemical alterations in the mussels can modify the energy fluxes of its metabolism, resulting in possible problems on the coastal systems used as cultivating sites.Key words: physiological parameters, multixenobiotic resistance mechanism, MXR, Perna perna, lead. RESUMOVariabilidade das taxas de filtração, assimilação e respiração e do mecanismo de resistência a multixenobióticos (MXR) no mexilhão Perna perna sob influência do chumbo A importância sócio-econômica que a mitilicultura conquistou no Estado de Santa Catarina explica a crescente procura por novos sítios costeiros para o seu uso. Estudos fisiológicos e bioquímicos do mexilhão Perna perna se apresentam como metodologias viáveis para programas de avaliação e monitoramento ambiental, permitindo inferir sobre a qualidade dos sítios e possíveis influências de agentes xenobióticos nas áreas costeiras. Com o objetivo de determinar a existência de variabilidade nesses parâmetros evocada pelo chumbo (1.21 µmol.L -1 ), mexilhões Perna perna foram mantidos à temperatura constante e alimentados com Chaetoceros gracilis por 15 dias. O grupo controle foi aclimatado em água do mar a 30‰. No final desse período foram realizados experimentos estáticos fisiológicos de filtração, respiração e assimilação, Braz. J. Biol., 62(4A)

Physiological studies of the mussel Perna perna in Brazil are almost 30 years behind those of other, more exhaustively investigated species, such as Mytilus edulis. Little is known about the variations in physiological rates due to size and the consequences of maintaining P. perna in laboratory conditions. This work investigated the variations in respiration, clearance, excretion and absorption efficiency rates of P. perna, classified by size and acclimatized in a laboratory, monitoring the mussels' respiration rates and biometry over a period of 30 days, in laboratory conditions. The respiration, clearance and excretion rates presented an allometric relation with the dry weight of the organisms, with b values of 0.66, 0.48 and 0.91 respectively. On the other hand, these same rates, when considered by weight (specific rates) showed a relationship that was inverse to the size of the organisms. Only the absorption efficiency was independent of the weight of the mussel. In terms of acclimatization, it was observed that it takes 10 days for the respiration rate of the mussel P. perna to stabilize in laboratory conditions, after which it follows a routine metabolism.Keywords: Perna perna, physiology, acclimatization, respiration, clearance, excretion, absorption efficiency. RESUMOTaxas fisiológicas do mexilhão Perna perna (Linnaeus, 1758) em diferentes classes de tamanho e condições de manutenção em laboratório O estudo da fisiologia dos mexilhões Perna perna no Brasil apresenta uma defasagem de aproximadamente 30 anos em relação a outras espécies mais exaustivamente investigadas como Mytilus edulis. O conhecimento acerca das variações das taxas fisiológicas em função do tamanho e as conseqüências da manutenção de P. perna em laboratório foram pouco estudadas. Neste trabalho, investigaram-se as variações das taxas de respiração, clareamento, excreção e a eficiência de absorção de P. perna aclimatados em laboratório em diferentes classes de tamanho, assim como foi realizado um acompanhamento de suas taxas respiratórias e de sua biometria ao longo de 30 dias de manutenção em condições laboratoriais. As taxas de respiração, clareamento e excreção apresentaram uma relação alométrica com o peso seco dos organismos, obtendo-se como valores de b de 0,66, 0,48 e 0,91 respectivamente. Por outro lado, estas mesmas taxas quando ponderadas pelo peso (taxas específicas) mostraram uma relação inversa com o tamanho dos organismos. A eficiência de absorção foi à única taxa que mostrou independência com o peso do mexilhão. Em termos de aclimatação, observou-se que o mexilhão P. perna leva 10 dias para estabilizar a sua taxa de respiração em laboratório, entrando em metabolismo de rotina.Palavras-chave: Perna perna, fisiologia, aclimatação, respiração, clareamento, excreção, eficiência de absorção. 326RESGALLA JR., C., BRASIL, E. S. and SALOMÃO, L. C.