饲料中脂肪水平对海湾扇贝性腺发育、脂肪酸组成和组织结构的影响

为了探讨配合饲料及其脂肪含量对海湾扇贝性腺发育、脂肪酸组成和组织结构的影响，在基础饲料中通过梯度添加鱼油（质量分数为0%、3%、6%和9%）配置4种脂肪质量分数为7%、10%、14%和17%的等氮饲料（质量分数为47%粗蛋白），分别记为F7、F10、F14和F17，并以小新月菱形藻（Nitzschia closterium f. minutissima）作为对照组，试验在室内1 000 L的水槽中进行，每种饲料随机投喂3组扇贝初始体质量为（40.79±1.70） g]，每个重复30只，试验周期30 d。结果显示：饲料中脂肪含量未显著影响扇贝死亡率（P>0.05），对照组死亡率显著低于各个饲料处理组（P<0.05）。性腺指数（gonadosomatic index，GSI）随着饲料脂肪含量增加呈先上升后下降的趋势，在F14组GSI达到最高，与对照组差异不显著（P>0.05），显著高于初始时期（P<0.05）。性腺中雌性部分含水量F10组最高，显著高于F17组（P<0.05）；雄性部分各处理组间差异不显著（P>0.05）。性腺中雌性部分粗脂肪含量显著高于雄性部分（P<0.05）。性腺中脂肪酸的含量PUFA>MUFA>SFA，饲料中脂肪含量显著影响性腺中SFA、MUFA、n-3PUFA、DHA和EPA的含量（P<0.05），当饲料中脂肪含量为14%或17%时达到最高值。性腺组织切片可见，各个处理组卵母细胞和精原细胞充满整个滤泡腔，滤泡密集，滤泡之间无空隙。由此可得出，配合饲料替代部分单胞藻饲喂海湾扇贝，可使其性腺发育至育苗要求，饲料中脂肪质量分数为14%时可以代替部分单胞藻饲喂海湾扇贝促进性腺发育。

Effects of dietary lipid on the gonad development, fatty acid composition, and histological structure of Argopecten irradias

A 30-day feeding experiment was conducted to investigate the effects of dietary lipid (mass fraction is 7%, 10%, 14%, and 17%) on the gonadal development, fatty acid composition, and tissue structure of Argopecten irradias. Four isonitrogen (mass fraction is 47% crude protein) feeds were formulated with the supplementation of graded levels of fish oil (mass fraction is 0%, 3%, 6%, and 9%). The scallops fed Nitzschia closterium f. minutissima served as control group. The scallops initial body mass:(40.79±1.70 g)] were stocked in glass reinforced plastic tank (1 000 L), and each diet was randomly allocated to three groups of scallops. (Result) Mortality rate was not significantly affected by dietary lipid, but mortality rate of control group was significantly lower than feed treatment (P< 0.05). The gonadosomatic index (GSI) showed an increased tendency first and then decreased with the increase of dietary lipid. The highest GSI was observed in scallops fed F14 diet, with no significant difference from control group (P> 0.05), significantly higher than the initial period (P<0.05). The highest moisture content of female gonad was observed in scallops fed F10 diet, significantly higher than that fed F17 diet (P< 0.05). The lipid content of female gonad was significantly higher than male gonad (P< 0.05). The SFA, MUFA, n-3PUFA, DHA, and EPA contents were significantly affected by dietary lipid (P< 0.05), and the highest content was observed in F14 or F17. The gonadal tissue sections showed that the follicular cavity was filled with oocytes and seminocytes. It was feasible to partially replace unicellular algae with formulated feed and the gonad could be developed to the requirement of seedling. These results above suggest that the optimal dietary lipid level for Argopecten irradias is about 14%.