Fernández-Reiriz M J, Labarta U, Albentosa M, Pérez-Camacho A
Consejo Superior Investigaciones Cientificas, Instituto de Investigaciones Marinas, Vigo, Spain.
Comp Biochem Physiol B Biochem Mol Biol. 2006 Jun;144(2):229-37. doi: 10.1016/j.cbpb.2006.02.015. Epub 2006 May 2.
This study investigates the influence of the lipid composition of microalgal and commercial flour diets on the lipid classes and fatty acids of Ruditapes philippinarum spat. Aspects of the nutritional role of the diets and the feeding ration are discussed with regard to previously published spat growth data. Our results demonstrated that clams showed the best growth rates when fed with diets that supplied a larger quantity of lipids, further characterised by a high content of phospholipids and triacylglycerols. We observed a significant correlation between the amount of triacylglycerols (r=0.929, p<0.05) and phospholipids (r=0.781, p<0.05) supplied and spat growth. In addition, R. phillipinarum spat reached the highest percentages of triacylglycerols (about 12%) and the lowest percentages of phospholipids (about 60%) and sterols (about 4%) with these growth-promoting diets. Spat fed with the other diets and/or rations showed lower growth rates and significantly lower quantities of triacylglycerols. In the present study, the alternative essentiality of 20:5n-3 and/or 22:6n-3 is confirmed. The diminishing supply of 22:6n-3 without an increase of 20:5n-3 has an effect on the growth of the spat. The dietary composition of fatty acids influenced the fatty acid profiles in bivalves. The results of our study would suggest that R. philippinarum is incapable of transforming 18:3n-3 to 20:5n-3 and then to 22:6n-3. Accordingly, although diets contained 18:3n-3, the spat reflected the low content of 20:5n-3 of the diets. With respect to 22:6n-3, given that this fatty acid is present in high quantities in Isochrysis, the spat content of this fatty acid was relative to its content in the diet. This study showed that clams with the lowest growth rates presented an increase in 20:4n-6. In the spat fed with the microalgal diets, 18:2n-6 scarcely reached 2% whereas in spat fed with wheat germ 18:2n-6 amounted to 18% of the total fatty acids. This fatty acid, by means of elongation, transforms to 20:2n-6, which also appeared in important quantities in the lipids of the spat fed totally or partially by wheat germ. We note that 20:2n-6 did not originate from the diet since it is absent in the microalgae and the flour. The desaturation of 20:2n-6 to 20:3n-6 has not been observed (low levels of 20:3n-6 in all cases) and therefore it can be assumed that the observed levels of 20:4n-6 were diet-related.
本研究调查了微藻和商业面粉饲料的脂质组成对菲律宾蛤仔稚贝脂质类别和脂肪酸的影响。结合先前发表的稚贝生长数据，讨论了饲料的营养作用和投喂量方面的问题。我们的结果表明，投喂提供大量脂质的饲料时，蛤仔的生长速度最佳，这些脂质的特征是磷脂和三酰甘油含量高。我们观察到所提供的三酰甘油量（r = 0.929，p < 0.05）和磷脂量（r = 0.781，p < 0.05）与稚贝生长之间存在显著相关性。此外，使用这些促进生长的饲料时，菲律宾蛤仔稚贝的三酰甘油含量达到最高百分比（约12%），磷脂（约60%）和甾醇（约4%）含量达到最低百分比。投喂其他饲料和/或投喂量的稚贝生长速度较低，三酰甘油含量也显著较低。在本研究中，证实了20:5n-3和/或22:6n-3的替代必需性。22:6n-3供应减少而20:5n-3不增加会影响稚贝的生长。脂肪酸的饲料组成影响双壳贝类的脂肪酸谱。我们的研究结果表明，菲律宾蛤仔无法将18:3n-3转化为20:5n-3，进而转化为22:6n-3。因此，尽管饲料中含有18:3n-3，但稚贝反映出饲料中20:5n-3的含量较低。关于22:6n-3，鉴于这种脂肪酸在等鞭金藻中大量存在，这种脂肪酸在稚贝中的含量与其在饲料中的含量相关。本研究表明，生长速度最低的蛤仔中20:4n-6含量增加。在投喂微藻饲料的稚贝中，18:2n-6几乎未达到2%，而在投喂小麦胚芽的稚贝中，18:2n-6占总脂肪酸的18%。这种脂肪酸通过延长转化为20:2n-6，在完全或部分投喂小麦胚芽的稚贝脂质中也大量出现。我们注意到20:2n-6并非源自饲料，因为微藻和面粉中均不存在。未观察到20:2n-6去饱和为20:3n-6（所有情况下20:3n-6水平均较低），因此可以认为观察到的20:4n-6水平与饲料有关。
