Cumaceans as a food source for the benthic cnidarian Halcampoides purpurea

Abstract

Cumaceans are peracarid crustaceans living in the sediment-water interface in all oceans and at all depths and they have been considered to be a permanent component of the suprabenthic communities. They can burrow into the sediment, thus obtaining protection from possible predators (Fig. 1a), but some littoral species also perform circadian migrations to the sea surface at night (Macquardt-Moulin 1991). Such migrations are undertaken mainly by males, which in most of the species have pleopods and a higher number of exopods that help them to swim better. The role of cumaceans in the marine food webs is poorly understood. They feed on epilithic diatoms by manipulating sand grains, on detritus by filtering water currents with plumose setae, or on benthic foraminifers that are captured by the piercing appendages present in some genera such as Campylaspis, which could be considered scavengers or even predators. In turn, these crustaceans seem to be the food source for a wide pool of predators (chaetognaths, cephalopod molluscs, decapod crustaceans, echinoderms, fishes, birds and even whales; information compiled from more than 140 papers). Within the cnidarians, cumaceans have only been reported as prey for the pelagic hydrozoan Velella velella and the benthic anthozoan Actinia equina. We offer here direct evidence of the capture of a cumacean (a male of the genus Iphinoe) by the anthozoan Halcampoides purpurea at night (Fig. 1b). This anemone inhabits sandy and muddy bottoms all around the world down to 1,000 m depth. It can alternate periods of activity and complete disappearance into the sediment. In marine caves this alternation could