Effect of dietary carbohydrates on gluconeogenesis in premolt Litopenaeus stylirostris juveniles and pre adults

Abstract

Because in the premolt stage L. stylirostris should produce glycogen to prepare chitin synthesis, the present paper was directed to answer the following questions: (a) Could an absence of dietary carbohydrates (CHO) enhance the gluconeogenesis pathway in premolt shrimp, following the trend in species of carnivorous fish? (b) In premoulting shrimp is it necessary to force the glyconeogenic pathway through intensive feeding or is a two meal/day feeding schedule enough? (c) Is the CHO metabolism adaptation affected by the age of shrimp? and (d) are the same mechanisms working in moult stage C and D?. A comparison with shrimp fed the same diets and in stage C has been done to determine the effect of the molt stage and dietary CHO levels in glycogen accumulation of this shrimp species. Results obtained showed that in stage D shrimp the gluconeogenlic pathway was enhanced, both in an intensive or in a two meal/day feeding schedule, independently of the age of the shrimp. The accumulation of glycogen to support both chitin synthesis and metabolic glucose is proposed as an explanation. Comparing the results obtained in the present paper with that of L. stylirostris juveniles published earlier, it is possible to observe that both in 12 hour fasting and during glycemia, the glycogen concentration in stage C shrimp was opposite of that observed in stage D shrimp. These results show that the intensity of the gluconeogenesis pathway changes with the molting stage, being of more importance in the premolt stage (D) than during the intermoult stage (C).