Nutritional value of different food sources for the benthic Daphnidae Simocephalus vetulus: role of fatty acids
Bec, Alexandre; Desvilettes, Christian Véra; Fontvieille, Dominique; Bourdier, Gilles
ArtNo.: ESP141015672001, Price: 29.00 €
In this experimental study, growth, survival and fecundity of the benthic Cladoceran Simocephalus vetulus were measured when feeding on Cryptomonas ovata, Paraphysomonas vestita, Cyclidium glaucoma and particulate amorphous organic matter to investigate the nutritional value of these food sources. Cladocerans fed Cr. ovata (autotrophic flagellate) exhibited the highest fecundity and growth. Particulate organic matter (POM, mainly composed of detrital particles) and Cy. glaucoma (ciliate) supported a lower grow and neonate production. P. vestita (heterotrophic flagellate) was inadequate to promote development and fecundity of S. vetulus and also resulted in high mortality. The concentrations of (n-3) series polyunsaturated fatty acids (PUFA) in the tested diets seemed to be the main factor determining their nutritional quality. S. vetulus' fecundity and increase in size were significantly correlated with the percentages of (n-3) PUFA in the diet, especially eicosapentaenoic acid (20:5 n-3). Although PUFA concentrations in Cy. glaucoma and POM were substantially lower than those provided by Cr. ovata, an apparent ability to bioconvert PUFA allowed S. vetulus to reproduce successfully. The fatty acid profiles of neutral lipids and phospholipids of the cladocerans indicate that S. vetulus is able to synthesise longchain PUFA from dietary C18 PUFA through a process of elongation and desaturation. However, the long chain (n-3) PUFA, especially 20: 5(n-3), in the lipids of P. vestita were apparently too scarce to be compensated for by bioconversion.