Thread-like tentacles in the Mediterranean corals Paramuricea clavata and Corallium rubrum

Abstract

The occurrence of modified tentacles (i.e. thread-like tentacles) in the Mediterranean octocorals Paramuricea clavata and Corallium rubrum is reported. Colonies of four species of Mediterranean gorgonians were maintained in aquarium conditions for more than 5 months. The development of thread-like tentacles has been observed only in two of the four species. The presence of modified tentacles in other cnidarians has been usually associated with defensive/aggressive behavior. Our observations showed that thread-like tentacles in P. clavata and C. rubrum can also be used for feeding.

An enigmatic new octocoral species (Anthozoa, Octocorallia, Malacalcyonacea) from Isla del Coco National Park

“…In that species, all eight tentacles of a polyp become modified (elongated with reduced pinnules and the tips swollen with nematocysts) in response to contact with spatial competitors. Similar elongation of the tentacles has been observed in the gorgonians Corallium rubrum (Linnaeus, 1758) and Paramuricea clavata (Risso, 1827), but hypothesized to function in feeding (Abel 1970;López-González et al 2018). The single enlarged tentacle observed in Aliena gen. nov. differs from the threadlike structures seen in these other species, but nonetheless represent a case of a modified tentacle whose main function is for competitive interactions or nutrition (Y. Benayahu pers.…”