Taxonomy and molecular phylogeny of the sea anemone Macrodactyla (Haddon, 1898) (Cnidaria, Actiniaria), with a description of a new species from Singapore

Supplementary materials (High resolution). Journal: <em>Zoological Studies</em>. Title: <em>Taxonomy and molecular phylogeny of the sea anemone Macrodactyla (Haddon, 1898) (Cnidaria, Actiniaria), with a description of a new species from Singapore</em>. ABSTRACT: Sea anemones (Cnidaria, Actiniaria) are a successful group of marine invertebrates found in a diverse range of environments globally. In spite of their ubiquity, identities for many sea anemones remain unverified, especially those from the Indo-West Pacific region. Here, we clarify the taxonomy of the poorly known <em>Macrodactyla aspera,</em> a shallow-water species first described from the Torres Straits in northern Australia. We re-describe <em>M. aspera</em> based on new morphological and molecular data gathered from the type specimen, other museum vouchers, and from fresh material collected from Singapore. We tested the monophyly of <em>Macrodactyla</em> using three mitochondrial (12S, 16S and cox3) and one nuclear (28S) marker based on three congeners, recovering this genus to be polyphyletic. As a consequence, we transferred <em>M. doreensis</em> to the genus <em>Heteractis</em>, and describe a new species, <em>Macrodactyla fautinae</em> sp. nov. While both<em> M. aspera </em>and <em>M. fautinae </em>sp. nov. share the same arrangement and number of complete mesenteries, a similar distribution of cnidae, and are not symbiotically associated with any other biota, <em>M. fautinae </em>sp. nov. has perforated, lobe-like verrucae on its column, and lacks nematocyst batteries on its tentacles, unlike <em>M. aspera</em>. These two species also occur in similar habitats in Singapore. Finally, because <em>M. aspera</em> strongly resembles Dofleinia armata, the latter species flagged as a danger to public health due to its ability to inflict painful stings, we tested the relationship between these species and found them not to be closely related. However, tentacles of <em>M. aspera</em>, like <em>D. armata</em>, are densely covered with nematocyst batteries and harbour large nematocysts; we infer that M. aspera may also be capable of delivering stings that endanger public health. This study builds upon a growing number of studies that aim to ascertain identities and systematics of sea anemones historically reported from the Indo-West Pacific. Our findings will facilitate accurate species identification, which is crucial for advancing research, formulating conservation measures, and protecting public health.