EFFECTS OF FISH OIL REPLACEMENT BY VEGETABLE OILS IN FATTENING DIETS ON THE RELATED GENE EXPRESSION OF FATTY ACID METABOLISM OF ADULT MALE CHINESE MITTEN CRAB, ERIOCHEIR SINENSIS

Fish oil is one of the major aquafeed ingredients, however, the world fish oil production could not meet the demand of global aquafeed industry. Thus, fish oil replacement have became a hot topic for the research and development of aquaculture. Chinese mitten crab Eriocheir sinensis is an important aquaculture species in China, and the previous study has shown the dietary substitution of fish oil with vegetable oil negatively impact the gonadal development and nutritional quality of this species possibly via lipid metabolism. The present study investigated the expression pattern of fatty acid metabolism-related genes, including fatty acyl elongase (Es-FAE), 9 fatty acyl desaturase (Es-FAD9), 6 fatty acyl desaturase (Es-FAD6b), fatty acid-binding protein 3 (Es-FABP3), fatty acid-binding protein 9 (Es-FABP9) and fatty acid-binding protein 10 (Es-FABP10), and their expression by different fish oil replacement levels (i.e. 0, 25%, 50%, 75% and 100%) in the hepatopancreas of E. sinensis. The results indicated that Es-FAE, Es-FAD9 and Es-FAD6b had the highest expression levels in hepatopancreas but low expression levels in heart and haemolymph, and that Es-FABP3, Es-FABP9 and Es-FABP10 were mainly distributed in hepatopancreas, muscle, seminal and accessory gland whereas the relatively low expression levels in stomach, intestine and heart. The Es-FAE-mRNA expression level in hepatopancreas significantly increased with the increasing dietary fish oil replacement levels. Diet 2# treatment had significantly higher Es-FAD6b-mRNA expression level than the Diet 3# treatment but no significant difference among other treatments. Decreasing dietary fish oil contents reduced the expression of the Es-FAD9 in hepatopancreas but without significant difference. (3) Diet 2# and Diet 3# but not other treatments significantly induced Es-FABP3-mRNA expression in hepatopancreas (P0.05). Dietary fish oil replacement did not significantly regulate Es-FABP9 and Es-FABP10-mRNA expression but had trend of low-high-low' in the hepatopancreas among the five treatmens. These results indicated that hepatopancreas had the highest mRNA expression of the genes related to fatty acid metabolism and transportation, and that dietary fish oil replacement had significant effects on their expression.