| The hormone levels of 17β-estradiol (17β-E2) and progesterone (PG) in the ovaries, hepatopancreas and hemolymph of female swimming crab, Portunus trituberculatus were determined during the reproductive cycle,their change pattern during this period were observed. Isolipidic and isonitrogenous diets were formulated to contain different DHA/EPA ratios(0.39, 1.24, 2.19, 2.89), HUFA levels(0.57%, 1.09%, 1.94%, 2.54%) and ARA levels(0.06%, 0.24%, 0.36%, 0.6%)by the supplement of semi-purified fish oil, and fresh clam diet as a control. Feeding experiments were carried out during the reproductive cycle, to investigate the effect of dietary HUFA on the ovary development, steroid hormone and tissue biochemical composition of swimmingcrab. The results are as follows:1. Changes of tissue steroid hormones in swimmingcrab Portunus trituberculatus during the reproductive cycle:1) The gonadosomatic index (GSI) increased significantly while the hepatosomatic index (HSI) keep relatively steady during the process of ovarian development.2) In stageⅡ, the progesterone concentration in all tissues reached peak, the PG levels began to decrease significantly at stageⅢ(P<0.05), the lowest PG level were observed in stageⅤ. Negative correlations were found between GSI and PG level in hepatopancreas, ovary and hemolymph.3) The 17β-E2 peak appeared in stageⅢ, then decreased gradually, the lowest level of 17β-E2 were alse observed in stageⅤ. Negative correlation was found between HSI and 17β-E2 level in hepatopancreas.4) PG concentration of all tissues showed significant positive correlations, as well as 17β-E2 levels in these tissues, this suggest the biosynthesis and metabolism of steroid hormones in swimmingcrab. 2. The effect of dietary DHA/EPA ratios on ovary development and lipid composition of swimmingcrab Portunus trituberculatus1) The dietary DHA/EPA ratio influenced HSI significantly, when the dietary DHA/EPA ratio of 2 or so, ovary developed satisfactorily and attained higher HSI.2) In the early phase, significant differences were found in moisture , lipid content and lipid class of hepatopancreas and ovary between 4 diet groups, whereas no significant different were found in the latter development phase.3) The fatty acid composition of hepatopancreas and ovary were influenced by the dietary fatty acid composition significantly.4) The dietary DHA/EPA ratio would affect hepatopancreatic albinism, higher or lower DHA/EPA ratio would result in higher rates of albinism.3. Effect of dietary HUFA level on ovary development, estradiol concentration in hemolymph and tissue lipid composition of swimming crab Portunus trituberculatus1) No significant difference was found in ovarian maturation, GSI, estradiol concentration in hemolymph, total lipid content and lipid class in ovary and hepatopancreas.2) HSI was influenced by dietary HUFA level significantly (p<0.05), high level of HUFA was not conducive to the accumulation of nutrients in the hepatopancreas;3) Significant positive correlations were observed between dietary fatty composition and the fatty composition of hepatopancreas and ovary4) Formulated diets might cause hepatopancreatic albinism, the morbidity of the highest HUFA Diet reached 45%, significant difference were found in biochemical composition and histological structure between albino hepatopancreas and normal hepatopancreas.4. The effect of dietary supplement of ARA on ovary development and tissue lipid composition1) No significant effect was observed by feeding different ARA level diet.2) Moisture, total lipid content and lipid class in hepatopancreas and ovary were not affected by dietary ARA level.3) Fatty acid composition of hepatopancreas and ovary reflected the diet fatty acid composition. |
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