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(70-75) Cadmium short-term toxicity in ionic and osmotic balance of Litopenaeus setiferus and Litopenaeus vannamei juveniles. Vanegas, Cecilia1, Zúñiga, Sebastián*,1, Amín, Oscar2, 1 Laboratorio de Ecofisiología. Facultad de Ciencias. Universidad Naciopnal Autónoma de México., México D.F., México D.F., México2 Centro Austral de Investigaciones Cintíficas., Ushuaia, Tierra del Fuego, Argentina ABSTRACT- White shrimp juveniles are efficient osmoregulators, capability that can be impair due increase of heavy metals in lagunar-estuarine ecosystems. The aim of this study was to evaluate and compare the effect of short-term cadmium exposure in osmoregulation of Litopenaeus setiferus and L. vannamei juveniles and their recovery potencial . Juveniles were exposed to sublethal levels of cadmium during 5 and 7 days and after that organisms were transfered to a cadmium-free medium during 7 and 14 days for recovery; cadmium-free control groups were considered. Bioassays were conducted at 28oC and 17 ups, the isosmotic point for both species. During exposure and recovery periods, hemolymph osmotic pressure and major ions (Cl-, K+, Na+) were evaluated as well as branchial Na+/K+ATPasa activity; metabolic rate was also measured as an integrated physiological response. In both species, osmoregulatory alterations were observed in greater degree due to exposure to the higher cadmium concentration; Na+/K+ATPase activity, ions and osmotic pressure were reduced by cadmium exposure. However normal levels were achieved at the end of the recovery period with exception of Na+/K+ATPase activity in L. setiferus exposed to the higher cadmium concentration suggesting a lower metal tolerance. Results suggest the participation of compensatory mechanisms to maintain internal medium and to reduce cadmium toxicity effects, corroborated by metabolic rate. While in L. setiferus oxygen consumption was increased during cadmium exposure, it was reduced in L. vannamei. Normal leves were achieved at the end of the recovery period in L. vannamei; however increased levels were maintained in L. setiferus. Different responses in metabolic rate suggest also different energetic strategies to confront short-term cadmium toxicity. Key words: cadmium, ionic-osmotic balance, Litopenaeus setiferus, Litopenaeus vannamei |
