Molecular diversity and patterns of co-occurrence of decapod crustaceans associated with branching corals in the central Red Sea

Crustaceans are one of the most widespread and speciose groups of marine organisms, fulfilling multiple ecological roles in numerous ecosystems. On coral reefs, many crustacean species form associations with scleractinian corals. Although the Red Sea is considered a biodiversity hotspot, few studies examined the diversity of coral-associated crustacean communities to date. In this study, 460 decapod crustaceans were recovered from 67 coral colonies of the three branching genera Acropora, Pocillopora and Stylophora in the central Saudi Arabian Red Sea. Crabs and shrimps were morphologically identified to the lowest taxonomic level possible, and portions of the mitochondrial COI and 16S rRNA genes were amplified with the objective of assessing their diversity and phylogenetic relationships. Finally, patterns of co-occurrence were evaluated to investigate the presence of species-specific symbiotic epifauna on different host corals. Overall, we recovered four families, five genera, and nine species of Red Sea crabs, nested into 11 molecular clades, and two families, eight genera and 11 species of shrimps, grouped within 12 lineages. Crabs of the species Trapezia tigrina were found to be exclusively associated with Pocillopora corals, while Tetralia crabs and the shrimps Jocaste japonica and Harpilius lutescens only occurred on Acropora colonies, providing evidence that potential loss of host corals due to local and global impacts could lead to consequent shifts in the symbiotic communities on reefs and to the loss of certain associated taxa. This study represents an advancement towards the understanding and molecular characterization of coral-associated benthic communities in the Red Sea and lays the ground for further research assessing the patterns of biodiversity, evolution, and ecological preferences of these organisms in the area.