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

Abstract

A net gain in long-chain polyunsaturated fatty acids (PUFA) occurs in Arenicola marina bioturbated mesocosms in the light and dark when brewery yeast is the only food. Fatty acid profiles were determined by GC-MS and quantified for system units. Bacterial fatty acid biosynthesis is indicated by accumulation of the bacterial fatty acids anteiso 14:0, iso 15:0, iso 16:0, anteiso 16:0, iso 17:0, C16:1n-7 and C18:1n-7 (cis-vaccenic acid). De novo production of longer chain PUFA within the worm tissues is implicated by a chain elongation converting linoleic acid (C18:2n-6) to C20:2n-6 and subsequent desaturation, resulting in a gain of arachidonic acid (C20:4n-6) and eicosapentaenoic acid (C20:5n-3) via the intermediary C20:3n-6. To test for the presence of PUFA-synthesising bacteria in system units, 495 cloned 16S rDNA fragments were compared with the databases and degenerate PCR primers were designed for the ketoacyl acyl carrier protein synthase gene highly conserved in the polyketide synthase region of known PUFA-synthesising Gammaproteobacteria. Gammaproteobacteria related to known PUFA producers were not abundant (<1% of clones) and PCR primers, whose specificity was confirmed by conspecific amplification of DNA product from genomic DNA of Shewenella frigidimarina 12253 T and Colwellia psychrethraea 8813 T , did not amplify product from mesocosm DNA samples. PUFA production is therefore primarily due to processes within the lugworm A. marina. Biosynthesis by invertebrates may be significant in benthic ecosystems and their culture has the potential to contribute to non-fishery sources of essential fatty acids required for aquaculture feeds.KEY WORDS: Fatty acid biosynthesis · Elongase · PUFA · Polychaeta · Marine food web · Arenicola marina · Aquaculture nutrition · Aquaculture feeds Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 387: [223][224][225][226][227][228][229][230][231][232][233][234][235][236][237][238][239] 2009 head shaft) lying above the feeding pocket and contribute to the diet, but algae are not utilised effectively (Rijken 1979) and the presence of cellulases has not been conclusively demonstrated (Longbottom 1970, nor since). On the other hand feeding on bacteria associated with enriched sand is considered likely. The short residence time of the ingested sand in the gut (Hüttel 1990, Chen & Mayer 1999 makes it unlikely that internal fermentation (as in ruminants) occurs; rather, the lugworm-bioturbated burrow/sand-substrate system may act as an external rumen in which bacteria are cultivated, ingested and digested -a process of food enhancement referred to as gardening (Plante & Mayer 1994. Feeding at depth on anaerobic sediment is most characteristic of A. defodiens (Cadman & Nelson-Smith 1993) but it is also observed in A. marina when feeding on sediments rich in organic material in nature (Cadée 1976) and in the laboratory (Rijken 1979), and is routinely observed in commercially farmed populations 1 (S. Craig unpubl. data, P. J. W...

Adding value to ragworms (Hediste diversicolor) through the bioremediation of a super-intensive marine fish farm

“…DHA is also an essential FA of great importance in marine fish nutrition. The significant increase in DHA concentrations in cultured specimens may be due to a selective retention in tissues and/or their ability to elongate FAs through a pathway that involves chain elongation of EPA and its desaturation to obtain DHA (Olive et al 2009). The absence of DHA in the tissues of wild specimens might reflect a deficiency of this FA in natural intertidal mud-flat food sources.…”

“…This FA can also be biosynthesized from linoleic acid (Bischoff et al 2009). It has been shown that, to some extent, polychaetes (Arenicola marina) have the ability to elongate 18:2n-6 (linoleic acid) to produce 20:2n-6, which through a desaturation pathway can yield de novo 20:4n-6 (Olive et al 2009). In addition, polychaetes can also retain most 20:4n-6 (AA) present in their diet (OM = 0.12 ± 0.02 µg g −1 DW).…”

Feeding preference of threadsail filefish Stephanolepis cirrhifer on moon jellyfish and lobworm in the laboratory

“…and the lipid content is only 1.0% (Saito et al 2006). Olive et al (2009) reported the EPA content of the lugworm Arenicola marina (Linne), another polychaete, to be 11.5% of the total fatty acid content. Arai (2005) reported that the calorimetric value of jellyfish per unit mass (wet basis) was less than 20% that of arthropods, implying that jellyfish contains fewer nutrients than other common prey item.…”

Phylogenetic characterisation of bacterial assemblages and the role of sulphur-cycle bacteria in an Arenicola marina bioturbated mesocosm

“…The faecal casts of A. marina are enriched in 14:0, i15:0, a15:0, 15:0, br17:0, 18:1n-7 and 18:1n-9, indicative of the presence of sulphate-reducing bacteria (Edlund et al 1985) and sulphur-oxidising bacteria (Conway & McDowell 1991). The presence of these same fatty acids in both wild-collected and mesocosm-cultured lugworm tissues is indicative of bacteriophagy (Olive et al 2009). …”

“…The mesocosm systems comprised plastic boxes (23 × 37 × 27 cm) maintained in a recirculation system (see Olive et al 2009 for further details). Beach sand from Cullercoats Bay, Northumberland, UK, was dried and sieved (mesh diameter 600 µm) before being added to cover the 'food' (brewers' yeast) until there was a yeast−sand combination layer about 4 cm high.…”