Lipid composition of Ruditapes philippinarum spat: Effect of ration and diet quality

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.Versión de editor

Response of two species of clams, Ruditapes decussatus and Venerupis pullastra, to starvation: physiological and biochemical parameters

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Wheatgerm flour in diets forManila clam, Ruditapes philippinarum, spat

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Effect of microalgal diets and comercial wheatgerm flours on the lipid profile of the Tapes deccusatus spat

The influence of both the lipid composition of microalgal diets and commercial flours on the lipid classes and fatty acids of Ruditapes decussatus spat was studied. These aspects of the nutritional value of the diets were discussed in relation to the growth of the spat. Four diets were tested; Diet A, composed of 100% of the daily food ration of microalgae; Diet B, composed of 100% of wheatgerm; Diet C, composed of 50% of microalgae and 50% of wheatgerm; and Diet D, composed of 25% of microalgae and 75% of wheatgerm. The microalgal cells present a higher lipid content than that for wheatgerm. Tahitian Isochrysis cells have phospholipids and triacylglycerols as majority lipids, whereas in the wheatgerm particles, the lipids more abundant are triacylglycerols. Fatty acid content was higher in the microalgal cells than in the wheatgerm particles. The n-3 fatty acids were the most abundant acids in the microalgae, whereas the n-6 fatty acids were in the wheatgerm. The n-3 PUFA were not detected in wheatgerm. Phospholipids were the main lipids present in the clam spat, followed by triacylglycerols. Other lipid classes, detected in significantly lower amounts, included free fatty acids, sterols, and sterol ester + waxes. The composition of fatty acids in the spat was influenced by the fatty acid composition of the diet. Highest spat growth rates were observed with those diets that present a higher phospholipid/triacylglycerol relation. A negative correlation in the relation n-6/n-3 vs. growth has also been observed, with better growth rates in diets with a lower ratio. If the fatty acid 20:5n-3 and 22:6n-3 considered “essential” for marine animals were not present in the diet, they were not present in the spat either. Desaturation and elongation capabilities of R. decussatus spat were also discussed

Comparative response of two species of clams, Ruditapes decussatus and Venerupis pullastra, to extreme nutritive stress: Physiological and Biochemical parameters

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Biomarkers of general stress in mussels as common indicators for marine biomonitoring programmes in Europe: The ICON experience

This study investigated whether general stress biomarkers in mussels can be applied as common first-tier biomarkers in regional biomonitoring programmes in the North Sea (including Iceland) and western Mediterranean Sea. Stress on Stress (SoS) and lysosomal membrane stability (LMS) biomarkers were analysed in resident mussels (Mytilus sp.) from 8 coastal sites and in transplanted mussels (Mytilus galloprovincialis) from two Spanish Mediterranean coastal sites. The assessment of results, as input to pollution monitoring strategies, was performed jointly for LMS and SoS data from the two regions. Contaminant body burden of the mussels was compared with biomarker results. The results demonstrated that these two general and non-expensive stress biomarkers in mussel can be applied throughout European waters, providing a cost-effective and harmonised approach to screen contaminant-related biological effects within the framework of wide-scale pollution biomonitoring programmes, such as that proposed by the European Union, i.e. the Marine Strategy Framework Directive.Postprint1,95