DNA metabarcoding to assess the diet of a highly toxic ribbon worm Cephalothrix cf. simula (Nemertea: Palaeonemertea)
Daria I. Melnikova, Alexei V. Chеrnyshev, Timur Yu. Magarlamov
Abstract
Nemertea is a phylum of predatory worms that feed on a wide range of invertebrates. Most studies on the diets of nemerteans have been conducted either through morphological identification of partially digested prey found in the intestines or via feeding experiments in laboratory. For the first time, we applied high-throughput sequencing of the hypervariable V9 region of the 18S rRNA gene to examine the diet of nemerteans. The nemertean Cephalothrix cf. simula, chosen for this analysis, possesses high concentrations of tetrodotoxin (TTX), a potent neurotoxin also found in other highly toxic marine animals. Nemerteans of this species use an everted proboscis to immobilize their prey and then swallow it whole. By analyzing 31 gut samples, we identified that C. cf. simula has a broad dietary spectrum, preying on polychaetes, crustaceans, hoplonemerteans, and flatworms. Polychaetes, specifically nereids and syllids, and planktonic copepods from the order Calanoida form the basis of the diet of C. cf. simula. Planktonic crustaceans were found in the diet of benthic nemerteans for the first time. Our results also show a significant difference in the number of dietary items between individuals containing high and low concentrations of TTX.