Aug 24, 1990 - (DANA, 1851). L. C. R. KUCHARSKI and R. S. M. DA SILVA. Departamento de Fisiologia, Centro de Endocrinologla Experimental, Instituto de ...
Comp. Biochem. Physiol.Vol.99A,No. I/2, pp. 215-218, 1991 Printed in Great Britain
0300-9629/91 $3.00+0.00 © 1991 PergamonPress plc
EFFECT OF DIET COMPOSITION ON THE CARBOHYDRATE AND LIPID METABOLISM IN AN ESTUARINE CRAB, CHASMAGNATHUS GRANULATA (DANA, 1851) L. C. R. KUCHARSKIand R. S. M. DA SILVA Departamento de Fisiologia, Centro de Endocrinologla Experimental, Instituto de Bioci~ncias, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 90.049, Brazil
(Received 24 August 1990) Abstract--1. The effects of a 15-day period of adaptation to a high-protein (HP) or carbohydrate-rich (HC) diet on the carbohydrate and lipid metabolism of Chasmagnathus granulata were investigated. 2. The carbohydrate-rich diet increases the blood glucose levels, the muscle and hepatopancreas glycogen and total lipids of the muscle. 3. With a high protein diet, the glycemia and glycogen of the hepatopancreas and muscle are low, and the total lipids are raised in these tissues. 4. This finding demonstrates the importance of the substrate input in regulating the energy metabolism of this crab.
INTRODUCTION The pattern of metabolic adjustment to energy metabolism in an animal may undergo changes according to variations of carbohydrate, protein, and lipid contents in the diet they are fed. Studies on body energy reserve storage control carried out both on vertebrates and invertebrates show the role played by diet composition in energy metabolism (Kettelhut et aL, 1980; Migliorini et aL, 1973; Veiga et aL, 1978; Higuera and Cardenas, 1985; Veldhuijzen and van Beck, 1976). The results of studies on energy metabolism in crustaceans have demonstrated that hormonal, environmental, and nutritional factors control glucose homeostasis (Santos et al., 1988; Sedlmeier, 1985; Dean and Venberg, 1965; Meenakshi and Scheer, 1961). The Chasmagnathus granulata crab lives on the supralittoral and mesolittoral zones of the salt marshes along the southern Brazilian coast (Boschi, 1964). Studies performed by Santos et al. (1987a,b; 1988) on this crab have demonstrated the effects of salinity, exposure to atmospheric air and crustacean hyperglycemic hormone (CHH) on the carbohydrate metabolism. As to the feeding habits of the Chasmagnathus granulata crab, studies performed by D'Incao et al. (1988) classified the alimentary behavior of this species as opportunist. The present experiments were designed to obtain information regarding the effect of diet composition on the energy metabolism in the Chasmagnathus granulata crab. For this purpose, the behavior of several related metabolic parameters was investigated in crabs adapted to a high-protein or carbohydraterich diet.
MATERIALS AND METHODS Experimental animals Male crabs in stage C of the intermoult cycle (Drach and Tchernigovtzeff, 1967), were collected in Tramandai Lagoon, Rio Grande do S u l , Brazil. Immediately after the field animals arrived at the laboratory they were weighed and measured and the glycemic values and the glycogen and total lipid contents of the hepatopancreas and muscle were determined in a group of crabs. The other animals were placed in aquaria at a salinity of 10%o, temperature approximately 20°C and daily photoperiod. The animals were divided into two groups, one of which was fed a high-protein, lowcarbohdyrate (HP) diet, while the other consumeda carbohydrate-rich (HC) diet, approximately isocaloric to the HP diet (Table 1). Both groups of crabs were fed daily (50 g) ad libitum in the morning for two weeks before being used in the experiments. No variation in body weight of the animals in both groups was found during the experimental period. Blood samples were obtained with a siliconized syringe from the blood sinus of the claw. For tissue analyses, the animals were anesthetized by hypothermia, and samples of hepatopancreas and muscle (claw) were quickly collected. All experiments'were performed in the morning between January and March.
Chemical analyses Blood glucose concentration was determined by the enzymatic oxidase method. Muscle and bepatopancreas glycogen was extracted essentially according to van Handel (1965) and determined as glucose after acid hydrolysis. Tissues lipids were determined gravimetrically after extraction by the procedure of Folch et aL (1957). Statistical analyses were performed by analysis of variance followed by multiple range testing, P < 0.05 was taken as the criterion of significance.
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L. C. R. Kucroa~srd and R. S. M. DA SILVA
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Table 1. Composition of HP and HC diet
Hepotoponc~l)os
HP diet (%wt/wt)
HC diet (%wt/wt)
21.59 0.03 6.71
3.34 34.56 0.45
Protein Carbohydrate Fat
HP=high protein; HC=high carbohydrates. The food was analysed by the Food Technology Institute at the Federal University of Rio Grande do Sul (ICTA/UFRGS).
5,0 -
HC • HP I B
4*° i 3~
RESULTS
2~
Figure 1 shows that the animals fed a HC diet presented significantly higher (P < 0.001) glycemic levels than those of the group fed the HP diet. The glycogen concentration was significantly higher in the muscles of animals kept on a HC diet than in those of the group fed a HP diet (Fig. 2). The same was found regarding the glycogen concentration in the hepatopancreas, which presented a significant increase (P < 0.01) over the values presented by the group maintained on the HP diet. In Figure 3 the comparison of the total lipid values in the muscle of the animals submitted to both diets did not present any significant difference (P > 0.05). However a 28% increase in the total lipid values in the hepatopancreas was found in animals given the HP diet, as compared to the animals on the HC diet, but the difference in relation to HC animals was not statistically significant. The results in Table 2 show that there is a significant reduction (P < 0.01) in the glycemia of animals fed the HP diet, as related to the field animals. However, plasma glucose concentration in HC did not differ significantly from that in field animals. On the other hand, the animals submitted to a HC diet presented a significant increase (P < 0.01) in the glycogen levels of the hepatopancreas and the muscle, as compared to the field animals. However, in the group fed the HP diet, an approximately 164% increase in the glycogen levels of the hepatopancreas
HC EB
HP BB 16.O
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2.° I Muscle 1.5 1.o
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Fig. 2. Changes in glycogen concentration of the muscle and hepatopancreas of animals submitted to different diets. Values are means + SEM. Number of crabs used in each experiment is indicated at the bottom of the column. HP = high protein diet. HC = high carbohydrate diet. and muscle was verified, but the differences in relation to field animals were not statistically significant (P > 0.05). A HP diet induced a significant (P
