| The Swimming crab,Portunus trituberculatus,is one of the important marine economic crabs.The artificial pond culture of swimming crabs has developed fast due to the gradual reduction of its wild resources.Researches have showed that the nutritional quality of farmed P.trituberculatus is not as good as that of wild-captured swimming crabs,which leads to the low price,unbalanced sales,and significant reduction of the economic value of swimming crab resources.Therefore,this study aims to make a basic discussion on the fattening and balanced sales of P.trituberculatus females through water environmental factor control and dietary nutrition regulation.1.Effects of water salinity on gonadal development,osmoregulation and physiological metabolism of adult female Portunus trituberculatusAs an important environmental factor,salinity plays an important role in the growth and gonadal development of crustaceans.A 30 days indoor trial of five levels of salinity(10,15,20 and 25)was conducted on P.trituberculatus females to explore the effects of different salinity levles on the fattening,ovarian development,osmotic regulation and physiological metabolism.The results show that:(1)No significant differences were found in the effects of different water salinity on hepatosomatic index(HSI)and gonadsomatic index(GSI),and the GSI in high salinity 25 were minimum;(2)Different water salinity levels had a significant influence on hemolymph osmolality and ion concentration,which increased with the water salinity on the whole,but K+ and Ca2+ concentrations had no significant differences between four groups(P > 0.05);The free amino acid content of hemolymph was lowest in low salinity(10 groups),with the Pro and Ala concentration changed most significantly;The ultimobranchial Na+/K+-ATPase activity was significantly elevated with the water salinity,but between 20 and 25 groups there was no significant difference(P > 0.05);(3)As for the effects of different water salinities on the metabolism performance,the contents of Urea and UA in hemolymph rised while the content of Glu reduced.In hepatopancreas,the UA content in salinity 25 group is significantly higher than that of other groups(P < 0.05);(4)For hepatosmatic antioxidant ability and immune property,the GSH-Px and MDA decreased with the water salinity,but T-AOC in salinity 20 group was significantly lower than other groups(P < 0.05);For the antioxidant ability and immune property of carbs hemolymph,GSH-Px,T-AOC and ?-GT achieved their lowest value in high salinity groups,while the ALP in the group of salinity 20 was higher than that in the group of salinity 25.In conclusion,low salinity can promote the rapid accumulation of ovarian materials,while the long-period low salinity status will inhibit the enzyme activity of osmotic regulation and physiological performance,that may cause irreversible damage of some tissues.To sum up,the moderate low water salinity will promote the fattening process of P.trituberculatus,with the recommanded water salinity not less than 15.2.Effects of dietary fish oil replacement by vegetable oils on ovarian development,lipid metabolism,antioxidant capacity and biochemical composition of adult female Portunus trituberculatusIn order to investigate the effects of dietary fish oil replacement with blending vegtable oils on the fattening performance,physiological metabolism and biochemical composition of adult female swimming crab(P.trituberculatus).Five isonitrogenous and islipidic fattening diets were formulated to replace 0%,25%,50%,75% and 100% of fish oil(defined asDiet 1-Diet 5)with blending vegtable oils(soybean oil: rapessed oil=1:1).The five fattening diets were fed to female P.trituberculatus(150 ± 25 g)for 45 days.The results showed as follows:(1)Dietary fish oil levels had no significant effects on survival rate,weight gain rate,gonadosomatic index and hepatosomatic index,meat yield and total edible yeild of adult female P.trituberculatus.(2)There were significant differences on the triglyceride(TG)content,malate dehydrogenase(MDH)lipase(LPS)and lipoprotein lipase(LPL)activities in the hepatopancreas among five diet treatments;the highest levels of TG and LPS were detected in Diet 5,the highest MDH was detected in Diet 1,while the highest LPL was detected in Diet 2.The highest TG and TC were detected in Diet 2 and Diet 3,respectively.(3)The hepatopancreatic peroxidase(POD)activity of the crabs in Diet 1 was significantly higher than that of Diet 2 and Diet 3,while the Diet 4 had the highest activities of hepatopancreatic alkaline phosphatase(ALP)and acid phosphatase(ACP).The highest and lowest values of total superoxide dismutase(T-SOD)activity in the hemolymph were detected at treatments of Diet 2 and Diet 1,respectively,while the highest hemolymph ALP activity was detected in Diet 1(P < 0.05).(4)Dietary fish oil replacement has significant effects on the contents of crude protein and total carbohydrate in muscle,and the highest levels of crude protein and total carbohydrate in the muscle were dected on Diet 3.There were significant differences in the contents of total lipid and total carbohydrate in the hepatopancreas among five treatments,and the higher levels of them were detected for Diet 3 and 4 treatments;moreover,the highest ovarian crude protein content was also detected on Diet 3 treatment.(5)Dietary fish oil replacement had significant effects on the fatty acid profile of muscle,ovary,and hepatopancreas;tissue n-6 polyunsaturated fatty acid(n-6 PUFA)increased with increasing dietary fish oil replacement level,while the contents of n-3 PUFAs and highly unsaturated fatty acid(HUFA)showed a decreasing trend.In conclusion,dietary fish oil replacement by vegetable oils had no siginificant effect on survival rate and fattening performance of adult female P.trituberculatus,but promote the TG,crude lipid and n-6 PUFA accumulations in the hepatopancreas as well as the POD and phosphatase;50% fish oil replacement level could increase the crude protein conetent of ovaries and muscle,while 100% fish oil replacement level decrease the HUFA content of hepatopancreas.3.Effects of dietary supplementation with Haematococcus pluvialis powder on ovarian development,coloration,antioxidant capacity and biochemical composition of adult female swimming crab,Portunus trituberculatusSwimming crab(P.trituberculatus)is an important mariculture crab,and the light color of the pond-reared crabs may be related to low level of dietary astaxanthin.This study was designed to investigate the effects of dietary astaxanthin on ovarian development,coloration,antioxidant capacity,immune performance and biochemical composition of female P.trituberculatus.Haematococcus pluvialis powder was used as natural astaxanthin source to formulate four experimental diets with different astaxanthin levels(0,26.60,41.62,and 81.37 mg/kg,defined as Diet 1#-4#).The four experimental diets were fed to female P.trituberculatus for 45 days during the ovarian development;therefore,there were four treatments in this study.The results show as follows:(1)Dietary astaxanthin had no significant effects on gonadosomatic index(GSI)and hepatosomatic index(HSI).(2)Total carotenoids content,redness(a*)and yellowness(b*)values of hepatopancreas,ovaries and carapace increased significantly with increasing dietary astaxanthin,while the lightness(L*)values of these tissues showed a decreasing trend(P < 0.05).(3)For antioxidant indices,the activities of super oxide dismutase(SOD)and peroxidase(POD)in treatments(Diet 2#-4#)with supplementation of astaxanthin were significantly lower than those in Diet 1# treatment without supplementation of astaxanthin.The activities of total antioxidant capacity(T-AOC)and glutathione peroxidase(GSH-Px)in hemolymph as well as the SOD,T-AOC in hepatopancreas increased significantly with elevated dietary astaxanthin,while a decreasing trend was found for the malondialdehyde(MDA)content in the hemolymph and hepatopancreas.(4)For the immune indices,Diet 4# treatment had the highest activity of acid phosphatase(ACP)in hemolymph and hepatopancreas,while Diet 1# treatment had the significantly higher hemolymph hemocyanin(Hc)content than other treatments(P < 0.05).(5)As for the biochemical composition,the increasing trend was found on the contents of total lipids and total carbohydrate in the muscle and hepatopancreas as well as ovarian lipids with increasing dietary astaxanthin,while Diet 2# treatment had the highest total carbohydrate content in the ovaries among the four treatments(P < 0.05).In conclusion,dietary supplementation of astaxanthin had no significant effect on ovarian development of P.trituberculatus,but could improve the coloration,antioxidant capacity and the contents of total lipids and total carbohydrate in edible tissues.These results suggest the appropriate level of astaxanthin in fattening diet was approximately 50 mg/kg for adult female P.trituberculatus. |
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