Dietary analysis of small planktonic consumers: a case study with marine bivalve larvae

Abstract

Establishing predator –prey relationships and determining competitive interactionswithin the plankton community remains a central aim of zooplankton ecology. Usingbivalve larvae as a model system, a DNA-based dietary approach using generaleukaryotic primers was evaluated. Prey DNA was preferentially amplified using apredator-specific endonuclease restrictio n enzyme and blocking primer. Application ofthe blocking primer in isolation resulted in 80% of recombinant clones carrying insertsof non-bivalve origin, increasing to 100% when combined with a restriction enzyme.Further validation was achieved using wild, naturally feeding larvae of Mysella spp. andOstrea edulis. Of the sequenced clones, 75% originated from centric and pennatediatoms (Bacillariophyta). A further 16% or iginated from fungi representing the phylaAscomycota and Basidiomycota. The rem aining sequences belonged to floweringplants (Magnoliophyta), single-celled green algae (Prasinophyceae), potential parasites(Ichthyosporea), dinoflagellates (Dinophyceae) and brown algae (Phaeophyceae). Noqualitative difference in diet was observed among these two particular species,although the diversity of prey observed suggests that this DNA-based approach is suitablefor studying the trophic interactions of marine bivalve larvae. Furthermore, based onsequence alignments, slight modifications to the blocking primer sequence could adaptthis basic approach to a wide diversity of consumers within the plankton community.KEYWORDS: bivalve; larvae; food web; trophic interaction; diet analysis; 18S rDNA