Preliminary DNA-based diet assessment of a gutless carnivore, the sponge Asbestopluma hypogea
Résumé
Deep-sea and underwater cave habitats are oligotrophic environments representing strong selective pressures for marine organisms. One family of sponges, Cladorhizidae, consists of very peculiar sponge species that have successfully colonised the deepest oceans as well as caves. They are not filter-feeders as every other Porifera but have evolved to become gutless carnivores. Assessing the diet of such organisms lacking a regular gut appears challenging using classic trophic ecological methods but is rather promising using molecular approaches. We here assessed the in situ diet of the carnivorous sponge Asbestopluma hypogea Vacelet & Boury-Esnault, 1995 by targeting the remaining prey DNA. Using 18S rDNA primers that do not amplify the sponge predator, we were able to amplify prey DNA over a large taxonomic range. DNA belonging to e.g. copepods, polychaetes, nematodes, brittle stars and mysids was detected. Some of these organisms were indeed visually identified as effective prey for the carnivorous sponge A. hypogea and these findings are in accordance with its opportunistic mode of feeding. When combined with stable isotope approach and morphological identification of captured prey, this method can be very useful to understand some of the diet of cladorhizid sponges. (C) 2015 Elsevier B.V. All rights reserved.