Co-occurrence of Hermodice carunculata (Polychaeta, Annelida) and Stichopathes spp. (Hexacorallia, Cnidaria) off Punta Blanca (SW Tenerife, Spain)

Abstract Marine Animal Forests (MAFs) in mesophotic ecosystems in some areas are mainly defined by Antipatharia (black corals). Among them, whip black corals (or unbranched corals) have a single-stem corallum and thrive in deeper habitats with strong currents. It has been suggested that the MAFs are biodiversity hotspots and may be seen as refugia and/or feeding areas for many species. The bearded fireworm, Hermodice carunculata , an omnivorous and opportunistic feeder that exhibits scavenging behavior, has been found in association with black coral forests; however, its co-occurrence with unbranched whip corals has not been previously documented and quantified. This study reveals the presence of H. carunculata alongside Stichopathes spp. in deep-water MAFs off Punta Blanca in Southwest Tenerife (Canary Islands), with a 40% co-occurrence rate in the video ROV transects. Highest values of both species were recorded at depths between 80 and 120 m. Correlations between H. carunculata and S. gracilis (r = 0.895) and S. setacea (r = 0.715) indicate positive relationships between the ecosystem engineer and the vagile species. These findings underscore the importance of MAFs in promoting biodiversity, highlight their vulnerability in a climate change world, and call for a deeper understanding of these ecosystems to inform conservation efforts.