Contribution of planktonic and benthic food sources to the diet of the reef-forming vermetid gastropod Dendropoma petraeum in the western Mediterranean

In the Mediterranean Sea, the vermetid Dendropoma petraeum (Monterosato, 1884) forms highly biodiverse reefs that have received increasing attention in recent years although very little is known about the food habit of this species. The main goal of this study was to describe the trophic role of planktonic and benthic food sources for D. petraeum. Specimens from three morphological zones of the reef (inner edge, cuvette and outer edge) at two sites with different wave exposure along the north-western coast of Sicily (Italy; western Mediterranean) were compared for d13C and d15N. Isotopic determinations were also carried out on potential food sources identified in epilithon, reef macroalgae and suspended particulate organic matter. d13C for D. petraeum showed significantly more depleted values in the more exposed conditions (i.e. the site with higher wave exposure and outer edge of the reef), while d15N did not differ appreciably. These results suggest greater exploitation of benthic sources in the sheltered than in the exposed site and reveal diet shift and trophic flexibility at a small spatial scale for the reef-former D. petraeum.