| Summary: | The use of DNA as a marker for prey inside the gut of predators has been instrumental in further understanding of known and unknown interactions. Molecular approaches are in particular useful in unavailable environments like the deep-sea. Trophic interactions in the deep-sea are difficult to observe in situ, correct deep-sea experimental laboratory conditions are difficult to obtain, animals rarely survive the sampling, or the study organisms feed during the sampling due to long hauls. Preliminary studies of vent and seep systems in the Nordic Seas have identified the temperate-cold water pelagic amphipod Themisto abyssorum as a potentially important predator these chemosynthetic habitats. However, the prey of this deep-sea predator is poorly known, and we applied Denaturing High Performance Liquid Chromatography (DHPLC) to investigate the predator - prey interactions of T. abyssorum in deep-water vent and seep systems. Two deep-water hydrothermally active localities (The Jan Mayen and Loki's Castle vent fields) and one cold seep locality (The Håkon Mosby mud volcano) in the Nordic Seas were sampled, genomic DNA of the stomachs of T. abyssorum was extracted, and 18S rDNA gene was amplified and used to map the stomach content. We found a wide range of organisms including micro-eukaryotes, metazoans and detritus. Themisto abyssorum specimens from Loki's Castle had the highest diversity of prey. The wide range of prey items found suggests that T. abyssorum might be involved in more than one trophic level and should be regarded as an omnivore and not a strict carnivore as have previously been suggested. OTU_best_rep_97_similarity Best representative sequences from each OTU based on 97% similarity. OTU_best_rep_98_similarity Best representative sequences from each OTU based on 98% similarity. OTU_best_rep_99_similarity Best representative sequences from each OTU based on 99% similarity. OTU_matrix_97_similarity A presence absence matrix for each OTU and specimen using 97% similarity to assign OTUs ...
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