Spatial Ecology of the Association between Demosponges and Nemalecium lighti at Bonaire, Dutch Caribbean

Coral reefs are known to be among the most biodiverse marine ecosystems and one of the richest in terms of associations and species interactions, especially those involving invertebrates such as corals and sponges. Despite that, our knowledge about cryptic fauna and their ecological role remains remarkably scarce. This study aimed to address this gap by defining for the first time the spatial ecology of the association between the epibiont hydrozoan Nemalecium lighti and the Porifera community of shallow coral reef systems at Bonaire. In particular, the host range, prevalence, and distribution of the association were examined in relation to different sites, depths, and dimensions of the sponge hosts. We report Nemalecium lighti to be in association with 9 out of 16 genera of sponges encountered and 15 out of 16 of the dive sites examined. The prevalence of the hydroid–sponge association in Bonaire reef was 6.55%, with a maximum value of over 30%. This hydrozoan has been found to be a generalist symbiont, displaying a strong preference for sponges of the genus Aplysina, with no significant preference in relation to depth. On the contrary, the size of the host appeared to influence the prevalence of association, with large tubular sponges found to be the preferred host. Although further studies are needed to better understand the biological and ecological reason for these results, this study improved our knowledge of Bonaire’s coral reef cryptofauna diversity and its interspecific associations.