On the coral-feeding habit of Peltaster placenta

The predatory activity of the asteroid Peltaster placenta (Müller and Troschel, 1842) on the black coral Parantipathes larix (Esper, 1790) is here described for the first time based on video footage obtained during a Remotely Operated Underwater Vehicle (ROV) survey conducted in the Pontine Archipelago (Southern Tyrrhenian Sea, Mediterranean Sea). Feeding is carried out on the living coenenchyme of the basal axis and pinnules of the antipatharian and is confirmed by the occurrence of its cnidocysts in the sea star gut content. The chitinous skeletal parts of the black coral are left intact as bare tissue, which helps to relate colonies to the predation event. Among all black coral species present in the research area, P. placenta was observed grazing exclusively on P. larix, similarly to other goniasterids known to be deep-sea corallivores with a marked selectivity for their prey. The predatory behaviour of P. placenta was previously unknown. The extent of its feeding traces suggests a significant influence on benthic trophic relationships and, ultimately, on the functioning, structure and health status of deep Mediterranean black coral forests.