The habitat formed by the Callogorgia species, with their abundance and colony sizes, provides an important refuge for a variety of brittle stars which are recognized as the epibionts of octocorals in both shallow and deep environments. In such a relationship, ophiurans benefit directly from being elevated because they facilitate their feeding by suspension, while octocorals do not seem to benefit or be harmed. During three different expeditions developed in the Colombian Pacific from 2012 to 2013 and in the Caribbean Sea during 1998 and 2012 by the INVEMAR - Marine and Coastal Research institute, different samplings were carried out on soft bottoms through trawls with an epibenthic net. For the Pacific Ocean, 33 fragments of the octocoral Callogorgia cf. galapagensis Cairns, 2018 with 178 specimens of the ophiuroid Astrodia cf. excavata (Lütken and Mortensen, 1899) were found in two stations at depths 530 and 668 m. Considering the abundance of A. cf excavata, other biological characters such as size, presence of mature gonads, and evidence of arm regeneration were also detailed. In contrast, in the Caribbean Sea, Callogorgia gracilis (Milne Edwards and Haime, 1857) was found with ophiuroids belonging to the genera Asteroschema and Ophiomitra. The octocoral Callogorgia americana (Cairns and Bayer, 2002) was also found, but without associated brittle stars. These findings constituted the first specific association reported in the Eastern Tropical Pacific, and new relationships for the Caribbean Sea. This further reflected a possible specific association between the Callogorgia and Astrodia species that needed to be further explored. Thus, the Callogorgia species and the brittle star A. cf. excavata represented new records for the Colombian Pacific Ocean and the southern Caribbean Sea.

To map ecological units in mesophotic coral ecosystems on the western side of San Andrés Island (Colombia) considering biotic components and geomorphic zonation among 30–140 m deep, 27 video transects were done using an ROV. In total, 14 h of video were recorded and 5742 still images were extracted from them, from which 753 met quality criteria for bottom coverage and organisms’ abundance estimations. These estimates were calculated from images through the Planar-Point Intercept method (PPI) using a 1 m × 0.5 m quadrant gridded 0.1 m × 0.1 m. CLUSTER, SIMPROF, and SIMPER analysis of benthic composition considering depth ranges in the group’s formation were done. The clusters formed were simplified and generalized using a color matrix to support the mapping process. Two geomorphological units were found, the deep reef terrace (30–60 m) and the reef slope (60–357 m), overlapping with five ecological units spanning 268 ha. The units Bioturbed sediments–Calcareous algae, Octocorals–Mixed corals, and Octocorals–Sponges sited on the deep reef terrace have been previously described in the shallow waters of the island, and the units Octocorals–Sponges–Antipatharians and Encrusting Sponges sited on the reef slope are described as new here. These findings contribute to the knowledge of Caribbean mesophotic coral ecosystems and are useful to update the Colombian coral reef atlas.