Abstract
Shallow water coral reefs are the most diverse marine ecosystems, but there is an immense gap in knowledge when it comes to understanding the diversity of the vast majority of marine biota in these ecosystems. This is especially true when it comes to understudied small and cryptic coral reef taxa in understudied ecosystems, such as mesophotic coral reef ecosystems (MCEs). MCEs were reported in Japan almost fifty years ago, although only in recent years has there been an increase in research concerning the diversity of these reefs. In this study we describe the first stoloniferous octocoral from MCEs, Hadaka nudidomus gen. nov. et sp. nov., from Iriomote and Okinawa Islands in the southern Ryukyus Islands. The species is zooxanthellate; both specimens host Cladocopium LaJeunesse & H.J.Jeong, 2018 (formerly Symbiodinium ‘Clade C’) and were collected from depths of ~33 to 40 m. Additionally, H. nudidomus gen. nov. et sp. nov. is both sclerite-free and lacks free pinnules, and both of these characteristics are typically diagnostic for octocorals. The discovery and morphology of H. nudidomus gen. nov. et sp. nov. indicate that we still know very little about stoloniferous octocoral diversity in MCEs, their genetic relationships with shallower reef species, and octocoral–symbiont associations. Continued research on these subjects will improve our understanding of octocoral diversity in both shallow and deeper reefs.
Highlights
Coral reefs make up only 0.2% of the earth’s ocean but are estimated to harbor a quarter of all marine species [1,2] and are the most diverse marine ecosystems on the planet
The ‘hotspot’ concept, a term used to mark a relatively restricted geographic area accommodating exceptionally high concentrations of biodiversity and endemism [7,8,9] has highlighted the wealth of species that are at risk and how localized such areas of richness can be [10]
In this study we formally describe the zooxanthellate, sclerite-free, and pseudopinnuled octocoral Hadaka nudidomus gen. nov. et sp. nov. from mesophotic coral reef ecosystems (MCEs) around Okinawa and Iriomote Islands
Summary
Coral reefs make up only 0.2% of the earth’s ocean but are estimated to harbor a quarter of all marine species [1,2] and are the most diverse marine ecosystems on the planet. There are vast gaps in knowledge concerning the majority of marine biota [11,12], making the recognition of biodiversity geographic patterns and hotspots questionable [13,14], as priorities identified for one taxon may not reflect the diversity of other taxa [14,15] This is especially true for understudied localities and environments, such as understudied coral reef ecosystems. Most work in the RYS has been conducted on the phyla Pisces, Crustacea, and Cnidaria, with the majority of research on hermatypic hard corals (Scleractinia) and, surprisingly, far less work on other commercially important groups such as Echinodermata and Mollusca, as well as on other understudied small and cryptic coral reef taxa [25] One such understudied small and cryptic group are octocorals belonging to the subordinal group, Stolonifera. In this study we formally describe the zooxanthellate, sclerite-free, and pseudopinnuled octocoral Hadaka nudidomus gen. nov. et sp. nov. from MCEs around Okinawa and Iriomote Islands
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