Opinions and declarations Rendered by the International Commission on Zoological Nomenclature

Opinions and declarations Rendered by the International Commission on Zoological Nomenclature

Corallimorpharia is an order of benthic cnidarians with a known global richness of 51 species, most of which are tropical and found in shallow-water habitats. These solitary organisms, which may occur in aggregations, are often overlooked compared to its more well-known sister group, Scleractinia (stony corals), as well as the closely-related Actiniaria (sea anemones) with which they are usually confused. Data on corallimorpharians in Singapore are sparse, though there are anecdotal photographic reports of various morphotypes at intertidal localities collated by citizen scientists. Combining these citizen-science observations and field collections, this study used both morphological and DNA sequencing approaches to establish the diversity and distribution of Corallimorpharia in Singapore. Based on a collection of 31 specimens and observational data from 23 coastal sites, examination of field photographs and gross morphology yielded nine distinct morphotypes. To infer their identities based on molecular data, three DNA loci were sequenced—mitochondrial intergenic region (IGR) between the cytochrome c oxidase subunits 1 (COX1) and 3 (COX3), part of the ATP synthase F0 subunit 6 gene (ATP6), and nuclear internal transcribed spacers (ITS). Phylogenetic analysis, supported by detailed examination of the internal and external morphology, recovered six morphospecies placed within four genus-level clades, including two species from Corynactis and Discosoma that are possibly new to science. The molecular phylogeny is nearly concordant with the morphological taxonomy and distinction between the Rhodactis species is equivocal, likely because of recent divergence and the limited number of molecular markers used. This study represents the first comprehensive inventory and phylogenetic analysis of corallimorpharians in Singapore that would facilitate further research in this understudied order.