GLYCOGEN LEVELS IN DIFFERENT TISSUES OF PACU (PIARACTUS MESOPOTAMICUS HOLRNBERQ. 1887)

Abstract

In order to determine the glycogen concentration in different tissues of pacu reared in captivity and if there are changes related to sex and month of the year, female and male fish (average body weight 2,387 g and body length 41.88 cm) were caught from ponds in four months (May, August, November and February). After 24 - 48 hours without food the fish were killed under anesthesia (MS 222) the liver and gonads were weighed to determine hepatosomatic index (HIS %) and gonadosomatic index (GSI %). Liver, white muscle, red muscle, heart and gonads samples were analyzed for glycogen levels determination by colorimetric method. The results show that liver is the main storing organ of glycogen. In the liver, the glycogen levels were low in May, increased in August, and showed a peak in November and February. Concentrations of glycogen in heart, white muscle, red muscle and gonads did not differ statistically either comparing sites or months of the year. The concentrations were the same in both female and male. HSI and GSI were lower in males and GSI did not differ between studied months, while in females the highest GSI was found in May. During the months, HSI showed changes not related to sex and presenting the lower levels in May.