摘要
为掌握刀鲚(Coilia nasus)胚胎及胚后发育早期的脂肪酸变化规律,采用生化分析手段对刀鲚的胚胎(原肠期,受精后7~9 h)、0日龄仔鱼(初孵仔鱼)、3日龄仔鱼和5日龄仔鱼(开口前)的脂肪酸组成和含量进行了检测分析。结果显示,刀鲚发育早期的总脂占干物质的相对含量均较高(53.10%~60.97%),干物质的总脂相对含量随个体发育显著降低,单个个体的总脂含量随个体发育呈现剧烈下降趋势,数值从胚胎的43.62μg/ind剧烈下降到5日龄仔鱼的16.27μg/ind;水分含量随个体发育而升高。刀鲚发育早期上述4个时期的干样中检出6种饱和脂肪酸(SFA)、4种单不饱和脂肪酸(MUFA)和8种多不饱和脂肪酸(PUFA)。4个发育时期脂肪酸相对含量,C18:1n9c占绝对优势(50.39%~57.00%),C16:1丰富且稳定(13.77%~14.24%),C16:0也较丰富(7.45%~9.15%)。单不饱和脂肪酸(MUFA)比例占绝对优势(65.14%~72.26%),n-3与n-6系列多不饱和脂肪酸含量的比值(∑n3PUFA/∑n6PUFA)较小(1.78~2.38)。刀鲚胚胎孵化出膜期间,单个个体单不饱和脂肪酸(MUFA)实际减少程度较高,尤其是C18:1n9c(减少量为13.21μg/ind,减少比例达到55.49%)和C16:1(减少量和比例分别为3.30μg/ind和53.12%),而二十碳五烯酸(EPA)加二十二碳六烯酸(DHA)的减少程度较低(1.44μg/ind和38.41%),尤其是DHA(0.95μg/ind和36.52%)。然而,出膜后,仔鱼对单不饱和脂肪酸(MUFA)的利用相对较低(1.94μg/ind和14.17%),尤其是C18:1n9c(13.21μg/ind和12.41%)和C16:1(0.63μg/ind和21.81%);而对EPA+DHA利用相对较高(1.04μg/ind和45.10%),尤其是DHA(0.71μg/ind和42.61%)。研究表明,刀鲚胚胎优先蓄留EPA和DHA,仔鱼在摄食前大量利用EPA+DHA(特别是DHA),呈现出海水鱼类脂肪酸的利用特点。因此,建议在刀鲚亲本强化培育及产后培育中,增加投喂富含单不饱和脂肪酸(MUFA)(特别是C18:1和C16:1)的饵料,以加强刀鲚亲本的营养积累和产卵后亲本生理机能的恢复;在刀鲚育苗前期,要及时补充富含DHA和EPA的饵料,如,单胞藻、蛋黄等,以提高刀鲚仔鱼开口期间的成活率。
Coilia nasus is an anadromous fish species with commercial importance and high market value in China, and it has a potential for aquaculture. In order to understand the value of changes in fatty acid compositions during embryonic and early post-embryonic development of C. nasus, the fatty acid compositions and contents at different developmental stages(embryos at 7-9 h of fertilization, newly hatched larvae at the age of 0-day, larvae at the age of 3-day, and larvae at the age of 5-day before feeding)were collected and analyzed by biochemical analysis methods. The experimental data were statistically analyzed with variance analysis. The results showed that the total lipid percent contents of C. nasus larvae at different developmental stages were high(53.10%-60.97%, Table 1), while decreased significantly with ontogenesis(P < 0.05, Table 1). The individual total lipid percent contents decreased sharply with ontogenesis(P < 0.05), and the value dropped dramatically from 43.62 μg/ind in embryos to 16.27 μg/ind in 5-day-old larvae(Table 1); while, the moisture increased significantly with ontogenesis(P < 0.05, Table 1). A total of 6 saturated fatty acids(SFA), 4 mono-unsaturated fatty acids(MUFA), and 8 poly-unsaturated fatty acids(PUFA) were found in the dry sample at different developmental stages(Table 2). The C18:1n9c content of C.nasus was the highest and had an absolute advantage at different developmental stages(50.39%-57.00%, P <0.05, Table 2), the C16:1 content was rich and stable(13.77%-14.24%, P > 0.05, Table 2), the C16:0 content was also rich(7.45%-9.15%)(Table 2). Simultaneously, the MUFA had an absolute advantage(65.14%-72.26%), the ratio of n-3 series poly-unsaturated fatty acids( ∑n3PUFA)/n-6 series poly-unsaturated fatty acids(∑n6PUFA) was low(1.78-2.38)(Table 2). During the incubation period, the degree of actual reduction of MUFA was higher, especially in C18:1n9c(13.21 μg/ind and 55.49%) and C16:1(3.30 μg/ind and 53.12%)(Fig. 2), while, the degree of actual reduction of C20:5 n3(eicosapentaenoic acid, EPA) + C22:6 n3(docosahexenoic acid, DHA) was lower(1.44 μg/ind and 38.41%), especially in DHA(0.95 μg/ind and 36.52%, Fig. 2). After hatch, at the endogenous feeding stage, the utilization rate of MUFA was lower(1.94 μg/ind and 14.17%), especially in C18:1n9c(13.21 μg/ind and 12.41%) and C16:1(0.63μg/ind and 21.81%, Fig. 3), while the utilization rate of EPA + DHA was higher(1.04 μg/ind and 45.10%),especially in DHA(0.71 μg/ind and 42.61%, Fig. 3). Therefore, EPA+DHA are preserved by priority during the C. nasus embryo incubation period, EPA + DHA(especially DHA) are largely consumed before the C.nasus larvae feeding, which is close to the fatty acids utilization characteristics of freshwater fish. In antepartum and postpartum cultivation of C. nasus brood stock, in order to improve the nutrition accumulation of brood stock and the recovery of physiological function of postpartum brood stock, diets enriched with the MUFA(especially C18:1 and C16:1) is suggested. In early larval breeding of C. nasus, in order to improve the survival rate of larvae, diets enriched with DHA and EPA(e.g., porphyridiophyceae and yolk) is also suggested.
引文
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