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| Macrodactyla fautinae Yap, Mitchell, Quek & Huang, in Yap, Mitchell, Quek, Tan, Tan et Huang, 2023. |
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 Macrodactyla aspera, a shallow-water species first described from the Torres Straits in northern Australia. We re-describe M. aspera 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 Macrodactyla 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 M. doreensis to the genus Heteractis, and describe a new species, Macrodactyla fautinae sp. nov. While both M. aspera and M. fautinae 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, M. fautinae sp. nov. has perforated, lobe-like verrucae on its column, and lacks nematocyst batteries on its tentacles, unlike M. aspera. These two species also occur in similar habitats in Singapore. Finally, because M. aspera 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 M. aspera, like D. armata, 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.
Key words: Actinioidea, Anthozoa, Intertidal, Integrative taxonomy, Southeast Asia.
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| Living individuals of Macrodactyla fautinae sp. nov., external morphology, in situ, top view. A, an expanded individual with a pale oral disc. B, another expanded colour morph with a dark-brown oral disc. Note that in both A and B, a pair of diametric bright pink dots marks the position of the siphonoglyphs. C, a contracted individual with adhesive, papillae-like verrucae at its distal end. Note that shell fragments are attached to the verrucae. D, an individual with much of its actinopharynx everted, obscuring the animal. E, a sea pen (Pteroeides sp.) being swallowed whole by a M. fautinae sp. nov. individual. Abbreviation: s, siphonoglyph; v, verrucae. Photographs by R Tan. |
Macrodactyla fautinae, sp. nov. Yap, Mitchell, Quek, and Huang
Natural history: Occurs as solitary individuals, at the middle intertidal in soft silty, sandy areas, and also found in seagrass meadows (Fig. 8A– E). Animal partially buried in substratum, distal end of animal exposed during the low tides, with small shell pieces, sand and/or rocks adhering to verrucae (Fig. 8C). Oral disc and tentacles typically expanded, with actinopharynx often everted and inflated outwards, in many instances obscuring the animal (Fig. 8D). This species has also been observed to swallow its prey whole (Fig. 8E). When disturbed, animal does not retract completely, tips of tentacles remaining partially exposed (Fig. 8C). In the process of contraction, water may also be expelled from verrucae-like structures, akin to a watering can.
Etymology: The name Macrodactyla fautinae sp. nov. honours the late Emeritus Professor Daphne Gail Fautin. Throughout her career, she had worked tirelessly to advance the knowledge of sea anemones.
CONCLUSIONS:
In this study, morphological and molecular evidence were integrated to re-diagnose the genus Macrodactyla and redescribe M. aspera. Furthermore, we provided historical, nomenclatural evidence to support the continued usage of the genus name. Since its first description by Haddon and Shackleton (1893), there have been very few published accounts of M. aspera, despite its wide geographical range across the Indo-West Pacific. The reason for this, we suspect, is that this species may have been misidentified as D. armata, due to its strong superficial resemblance. Museum vouchers we have examined support this assertion; some were indeed misidentified as D. armata. Herein, we provided molecular evidence to demonstrate that these two species are distantly related.
Findings from this study add to a growing number of sea anemone species recorded from Singapore. Previous studies have already documented 37 species to occur on the shores and islands of this city-state (e.g., England 1987; Fautin et al. 2009; Yap et al. 2021). Affirming the identities of these sea anemones primes new avenues where more Indo-West Pacific species may be included in future research.
Nicholas Wei Liang Yap, Michela Lee Mitchell, Zheng Bin Randolph Quek, Ria Tan, Koh Siang Tan and Danwei Huang. 2023. Taxonomy and Molecular Phylogeny of the Sea Anemone Macrodactyla (Haddon, 1898) (Cnidaria, Actiniaria), with a Description of A New Species from Singapore. Zool Stud. 62:29. DOI:10.6620/ZS.2023.62-29
