Qualitative assessment of the diet of European eel larvae in the Sargasso Sea resolved by DNA barcoding

Abstract

European eels (Anguilla anguilla) undertake spawning migrations of more than 5000 km from continental Europe and North Africa to frontal zones in the Sargasso Sea. Subsequently, the larval offspring are advected by large-scale eastward ocean currents towards continental waters. However, the Sargasso Sea is oligotrophic, with generally low plankton biomass, and the feeding biology of eel larvae has so far remained a mystery, hampering understanding of this peculiar life history. DNA barcoding of gut contents of 61 genetically identified A. anguilla larvae caught in the Sargasso Sea showed that even the smallest larvae feed on a striking variety of plankton organisms, and that gelatinous zooplankton is of fundamental dietary importance. Hence, the specific plankton composition seems essential for eel larval feeding and growth, suggesting a linkage between eel survival and regional plankton productivity. These novel insights into the prey of Atlantic eels may furthermore facilitate eel larval rearing in aquaculture, which ultimately may replace the unsustainable use of wild-caught glass eels.

Figure 1.

Neighbour-joining tree showing prey sequences (approx. 500 bp) obtained from A. anguilla gut samples (marked in red, eel larvae diet (ELD)) and 18S rRNA gene sequences from GenBank (in italics followed by the accession number). For collapsed groups, the number of sequences per group is given within brackets. Bootstrap values greater than 50% (2000 replications) are shown above branches. Drawings illustrate potential free-living prey within each group. Scale bar indicates nucleotide substitutions per site.

Figure 2.

Frequency of prey taxa in guts of 42 larvae of A. anguilla.