Comp. Biochem. Physiol. Vol. IOZC, No. 2, pp. 241-252,1992 Printed in Great Britain 0306-4492/92 $5.00 + 0.00 Pergamon Press Ltd CHANGES IN BIOCHEMICAL COMPOSITION OF GILLS, HEPATOPANCREAS AND MUSCLE OF THE RED CRAYFISH PROCAMBARUS CLARK11 (GIRARD) AFTER SUBLETHAL EXPOSURE TO MERCURY AMPARO TORREBLANCA, JOSE DELRAMO and JAVIER DIAZ-MAYANS Laboratory of Animal Physiology, Department of Animal Biology, Faculty of Biological Sciences, University of Valencia, Dr Moliner 50, 46100-Burjassot, Valencia, Spain (Receioed 8 October 1991) Abstract-l. The changes in the biochemical composition of gills, hepatopancreas and muscle after exposure to 0.25 mg Hg/l were studied in Procambarus clurkii. 2. Sublethal exposure to mercury in P. clurkii resulted in significant decreases in protein concentration and caloric concentration in gills over the 96 hr period. Glycogen/lipid and glycogen/protein ratios increased after 48 and 96 hr of mercury exposure. 3. Lipid and caloric concentration in the hepatopancreas were significantly lower in 96 hr mercury exposed group. 4. Glycogen concentration in muscle was depleted as consequence of 96 hr mercury exposure. INTRODUCTION Metal ions are serious pollutants, especially in the aquatic environment, since they can be incorporated into food chains and concentrated by aquatic organ- isms to a level that affect their physiological state. Mercury compounds enter the biological environ- ment from natural discharges and anthropogenic sources. Although there is a trend in reducing indus- trial use of mercury, high concentrations of the metal are still present in sediments of lakes, ponds and rivers. Mercuric chloride is one of the most toxic metallic salts found in the aquatic environment. Acute toxicity of mercury on marine and freshwater crustaceans has been extensively studied (Eisler, 1987; World Health Organization, 1989). Some sublethal effects of mercury on respiration, metabolic activity and osmoregulation in these invertebrates have also been reported (Corner and Sparow, 1956; Depledge, 1984; Diaz Mayans et al., 1986; Torreblanca et al., 1989). The American red crayfish Procambarus clarkii is the most cosmopolitan of crayfish species. This crayfish can live in a wide range of environmental conditions which includes highly polluted waters (Del Ramo et al., 1988; Madigosky, 1991). P. clarkii must alter all or part of its physiological and bio- chemical processes to maintain homeostasis and to deal with pollutant-induced stress. Coping with fluc- tuating habitats must also require some energy expen- diture (Giesy et al., 1988). A number of studies examined changes in body composition occurring in crustaceans in response to molting or nutritional stress (Hazlett et al., 1975; Schirf et al., 1987). However not many studies ad- dressed the effects of metal-induced stress on the energy reserves of these organisms (Dickson et al., 1982; Radhakrishnaiah and Busappa, 1986; Torre- blanca et al., 1991). Adenylate energy charge (AEC) has been proposed as an indicator of both sublethal stress and physio- logical well-being in aquatic animals (Haya and Waiwood, 1983). However, in some organisms the AEC compensates perfectly in response to stress whereas energy precursors such as carbohydrate, protein and lipid are altered. Harms et al. (1990) reported a correlation between the amount of nucleo- tides and the concentration of reserve substances in Carcinus maenas larvae, showing that larvae can regulate their energetic pool as long as they can metabolize reserve substances. Caloric content (calcu- lated from the energy equivalence of protein, glyco- gen and lipid) is an index that offers an integrated parameter of the long-term energy reserves. A re- duction in the caloric content of crustaceans exposed to several toxicants has been observed (Capuzzo et al., 1984; Graney and Giesy, 1986; McKee and Knowles, 1986). These studies measured the caloric content of the whole organism. Neither energy re- serves or toxicants are equally distributed among different organs and tissues. The consideration of toxicant effect on the composition of each organ can bring more insight both in the understanding of the mechanism of the toxic effect and in the long-term significance of these alterations. The purpose of this study was to examine changes in energy reserves in the gills, hepatopancreas and dorsal tail muscle of the crayfish P. darkii, in response to sublethal exposure to mercury. MATERIALS AND METHODS Adult intermolt specimens (males and females) of P. clarkii were collected from Lake Albufera (Valencia, Spain) and carried immediately to the laboratory where they were transferred into 300-l aquaria. They were maintained and starved for 15 days at 20°C. Afterwards, they were fed pork liver ad libitum. Two days after feeding crayfish ranging in 247