Influence of food regimes and seasonality on fatty acid composition in the ragworm

Abstract

Nereidid worms are well known to be key prey species for aquatic organisms, including economically important fish (e.g. plaice) and invertebrates (shrimps). Food regimes which include nereidids improve the reproductive fitness of cultured animals, i.e. the 'nereidid effect'. Aquaculture produces huge amounts of sludge, which might be recycled by feeding to the ragworm Nereis diversicolor. Here we analysed the fatty acid profiles in N. diversicolor over 1 yr for a wild population and for ragworms fed with commercial fish food or eel sludge. The omega-3 (ω-3) eicosapentanoic acid (20:5n3) was the most abundant fatty acid followed by palmitic (16:0), stearic (18:0) and oleic (18:1) acids. Biomass of the ragworms increased by 205% in worms fed with fish food and remained stable in worms fed with eel sludge, indicating the good adaptation of individuals to the culture conditions. Only under fish food regimes were significant increases observed in saturated and total unsaturated fatty acids compared to natural food regimes. However, the ω-3 polyunsaturated fatty acids did not differ among food regimes, indicating that sludge from aquaculture is a good nutritive resource for N. diversicolor. This suggests the potential use of ragworms in aquaculture to reduce the production of waste and increase the reproductive fitness of cultivated animals.

Net gain of long-chain polyunsaturated fatty acids (PUFA) in a lugworm Arenicola marina bioturbated mesocosm

“…The source of the relatively small amount of DHA produced within the system units that accumulated in the lugworm tissues remains problematical. We do not exclude a bacterial origin for this, perhaps from the small number of Shewenella-or Colwellia-like Gammaproteobacteria present in the system (Ashforth 2008).The fatty acid profiles of other polychaetes whose fatty acids have been characterised is consistent with a widespread occurrence of the proposed pathway in the polychaete clade based on evidence reported for Nereis (Hediste) diversicolor (Bradshaw et al 1990, Luis & Passos 1995, Fidalgo e Costa et al 2000, García-Alonso et al 2008, Nereis virens (Olive et al 2002), a number of deep-sea vent worms (Taghon 1988, Pond et al 2002, Phleger et al 2005) and cold-water detritivorous species (Copeman & Parrish 2003), all of which show the occurrence and prominence of C20:2n-6 (the elongation product of C18:2n-6 from which C20:3n-6 is derived) and lack or low concentration of fatty acids associated with the conventional n-6 and n-3 pathways. The presence of long-chain unsaturated fatty acids in deep-sea vent worms has been considered problematic because of the general acceptance that these fatty acids are normally derived from the abundant sources present in the photic zone (for discussion see Pond et al 2002, Phleger et al 2005.…”

“…This provides clear evidence of a dietary independence for many longer chain PUFA which must therefore have been produced within system units. García-Alonso et al (2008) similarly found that the fatty acid profile of the polychaete Nereis diversicolor did not change seasonally and was not noticeably influenced by the fatty acid content of their diets. This implies the existence of mechanisms by which long-chain fatty acids can accumulate in detritivorous polychaete tisses from non-photosynthetic sources.…”

“…Taghon 1988, Fidalgo e Costa et al 2000, Copeman & Parrish 2003, García-Alonso et al 2008. The origin of the fatty acids in benthonic, easily cultured polychaete worms, such as Nereidae and Arenicolidae, has assumed an economic importance because their fatty acid content, coupled with their high palatability, has lead to their inclusion as a component of aquaculture brood stock diets (Izquierdo et al 2001).…”

“…These sources could include bioreactors designed to amplify naturally occurring pathways (Bergé & Barthanan 2005). Polychaetes have become well established as dietary components for shrimp and finfish hatcheries (Izquierdo et al 2001, García-Alonso et al 2008 for recent discussion), which have in turn resulted in the emergence of a polychaete farming sector in Europe and Southeast Asia. Our small-scale mesocosm study demonstrates that the biosynthesis of long-chain fatty 237 Mar Ecol Prog Ser 387: 223-239, 2009 acids occurs in the absence of light in polychaetebioturbated marine sediments to which a fermented yeast substrate has been added, and the amplification of naturally occurring ecosystem components in aquaculture production systems, e.g.…”

Nutritional status of a nereidid polychaete cultured in sand filters of mariculture wastewater

“…However, their supplies are still largely dependent on wild populations, so can be affected by overfishing and habitat disturbances (Scaps 2003). Also, their nutritional contents are known to vary according to seasonal and environmental conditions (Garcia-Alonso et al 2008), and their biosecurity status has recently been questioned (Vijayan et al 2005). These factors suggest that alternative feeds or alternative production strategies for suitable polychaete species are needed.…”