False corals (Anthozoa: Corallimorpharia) from a South Caribbean upwelling area: taxonomy, microhabitat, and associated fauna

Corallimorpharians (false corals) are important components of tropical coral reef communities, yet their taxonomy, distribution and natural history remain poorly documented in the south Caribbean, where most available studies date back to the 1970s. Given the accelerating impacts of global environmental change on tropical marine ecosystems, improved knowledge of these ecologically relevant yet understudied organisms is a pressing need. Using SCUBA-based surveys, we surveyed 19 stations (corridors of 10 x 2 m parallel to the coastline) between 7 and 44 m of depth in the South Caribbean upwelling region of Tayrona National Park, Colombia. Field observations of type of substrate, microhabitat (area between 12 and 15 cm around the crown of tentacles) and associated sessile and mobile fauna were combined with histological and cnidome analyses. We examined 3,462 specimens belonging to five corallimorpharian species, including Ricordea florida (n = 3,104), Orinia torpida (n = 171), Discosoma carlgreni (n = 108), Rhodactis osculifera (n = 75) and D. neglecta (n = 4). Discosoma carlgreni, D. neglecta, and O. torpida are recorded for the first time in Colombia and the southern Caribbean. We also provide new ecological (substrate, associated fauna and distribution), morphological (oral tentacle morphology, coloration and size), and cnidome (expanded size range and tissue-specific nematocyst types beyond previous reports) observations that support the taxonomic distinction of O. torpida from the genus Rhodactis. Our findings expand the known diversity and distribution of corallimorpharians in the southern Caribbean and provide a baseline for future taxonomic, ecological and biogeographic studies of this overlooked anthozoan group.