Seasonal variations in the intermediate metabolism of the crayfish Parastacus brasiliensis (Crustacea, Decapoda, Parastacidae) in the natural environment and experimental culture

The goal of this study was to evaluate the effects of seasonal variations on energy metabolism in different tissues of the freshwater crayfish Parastacus brasiliensis (von Martens, 1869). Crayfish were collected monthly from January 2001 to January 2003 in São Francisco de Paula, Rio Grande do Sul, Brazil, in a stream and in a culture tank. Haemolymph samples were collected from each crayfish in the field with a syringe, by puncturing the membrane at the base of the chelipeds. Hepatopancreas, gills, and abdominal muscle were removed for determination of free glucose, glycogen, total lipids, and triglycerides. The haemolymph samples were used for determination of glucose, total proteins, total lipids, and triglycerides. Statistical analysis revealed significant differences in biochemical composition in crayfish collected in the stream compared to the experimental tank during the year, principally in glucose and triglycerides in haemolymph, glycogen and total lipids in all tissues study, and triglycerides only in abdominal muscle. The regular food intake partially modified these seasonal variations of the metabolic pattern. Environmental conditions (e.g., food availability and water temperature) and reproductive period appeared to be the main factors influencing the seasonal patterns of variation in energy metabolism.<br>O objetivo deste estudo foi avaliar o efeito das variações sazonais no metabolismo energético em diferentes tecidos do lagostim de água-doce Parastacus brasiliensis (von Martens, 1869). Os lagostins foram coletados mensalmente de Janeiro de 2001 a Janeiro de 2003 em São Francisco de Paula, Rio Grande do Sul, Brasil, no riacho e no tanque de cultivo. Amostras de hemolinfa foram coletadas de cada lagostim em campo com seringa, por punção na membrana da base dos quelípodos. Hepatopâncreas, brânquias e músculo abdominal foram removidos para a determinação dos níveis de glicose livre, de glicogênio, de lipídios totais e de triglicerídeos. As amostras de hemolinfa foram utilizadas para a determinação dos níveis de glicose, de proteínas totais, de lipídios totais e de triglicerídeos. As análises estatísticas revelaram uma variação significativa na composição bioquímica dos lagostins coletados no riacho quando comparados com os do cultivo experimental durante o ano, principalmente da glicose e dos triglicerídeos na hemolinfa, glicogênio e lipídios totais em todos os tecidos estudados, e dos triglicerídeos somente no músculo abdominal. O aporte regular de alimento modificou parcialmente estas variações sazonais do padrão metabólico. As condições ambientais (ex.; disponibilidade de alimento e a temperatura da água) e o período reprodutivo parecem ser os principais fatores a influenciar os padrões sazonais da variação do metabolismo energético

Seasonal variation of the effect of high-carbohydrate and high-protein diets on the intermediate metabolism of Parastacus brasiliensis (Crustacea, Decapoda, Parastacidae) maintained in the laboratory

The goal of this study was to evaluate the effect of a high-carbohydrate diet (HC) and a high-protein diet (HP) on the metabolism of the crayfish Parastacus brasiliensis (Von Martens, 1869), collected in different seasons and maintained in the laboratory for 15 days. Crayfish were collected monthly from January 2002 to January 2004 at São Francisco de Paula, Southern Brazil, in Guarapirá stream. In the laboratory, the animals were kept submerged in aquariums under controlled conditions. They were fed ad libitum, for 15 days with either a HC or HP diet. At the end of this period, haemolymph samples were collected, as were hepatopancreas, gills, and abdominal muscle that were removed for determination of glycogen, free glucose, lipids, and triglycerides. The haemolymph samples were used for determination of glucose, proteins, lipids, and triglycerides. Statistical analysis (ANOVA) revealed significant seasonal differences in biochemical composition in crayfish maintained on HC or HP diets. Independent of the diets offered to the animals and the controlled conditions for 15 days, the indications of seasonality were unchanged. The observed changes seemed to be related to the reproductive period. Moreover, the HC diet increased all energy reserves in adult parastacids, which may aid in reproduction