Research Article |
Corresponding author: Makoto Kato ( kato@zoo.zool.kyoto-u.ac.jp ) Academic editor: Richard Willan
© 2017 Makoto Kato, Luna Yamamori, Ryutaro Goto, Remi Tsubaki, Ken Ohsuga.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Kato M, Yamamori L, Goto R, Tsubaki R, Ohsuga K (2017) A new large tellinid species of the genus Pharaonella from the Ryukyu Archipelago, Japan (Mollusca, Bivalvia). ZooKeys 705: 1-13. https://doi.org/10.3897/zookeys.705.12888
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A new tellinid species, Pharaonella amanyu sp. n., is described from sand banks around Amami Islands, the Ryukyu Archipelago, in southern Japan. A molecular phylogenetic analysis suggests that this new species is closely related to P. sieboldii. This species has long siphons and lives buried deep in well-sorted white sand syntopically with Tonganaella tongana. These rare, large tellinid species are indicators of unspoiled tidal/subtidal sand flats, which should receive the highest priority conservation in the Ryukyu Archipelago.
Amami Island, bivalve, coral reef ecosystem, sand flat, Tellinidae
Coral reef ecosystems often contain sand flats in which the sediments are mainly composed of coral sand. Even though the biodiversity of tropical coral reefs is both extremely high and the species themselves sometimes endangered (
The sand flat is characterised by a diverse fauna of tellinid bivalves, which are surface deposit feeders with colourful thin shells and long extensible siphons. The genus Pharaonella (Lamy, 1918) and the recently described Tonganaella Huber, Langleit & Kreipl, 2015 are both characterised by large narrow shells with rostration posteriorly, and both occur in tidal and subtidal sandy substrata, where they are buried deeply and extend their long siphons up to the surface of the sediment. In these genera, four species are presently known from Japan: T. perna (Spengler, 1798); T. tongana (Quoy & Gaimard, 1835); P. aurea (Perry, 1811); P. sieboldii (Deshayes, 1855). In this survey on Edateku Island, several shells of an unidentified tellinid species belonging to one of these genera were collected. The shells resemble the Pharaonella sp. reported from Amami Islands by
In this paper, this bivalve is described as a new species, its special habitat reported, and the conservational priority of the unspoiled intertidal/subtidal sand banks bounding a strait between coral reefs is emphasised.
An intertidal/subtidal sand flat is present along the eastern coast of Edateku Island in the northern Ryukyu Archipelago, Kagoshima Prefecture, Japan (28°17'26.08"N, 129°13'9.09"E) (Fig.
To characterise the molluscan biodiversity of the sand flat, we sampled the molluscs, particularly the tellinid bivalves, by digging the sand with shovels at low tide during the spring tides in May or June each year from 2005 to 2016. Three Tonganaella/Pharaonella species were found in these samples: T. perna (Spengler, 1798), T. tongana (Quoy & Gaimard, 1835) (Fig.
Sequence data were obtained for the mitochondrial cytochrome c oxidase subunit I (COI) gene, nuclear 28S ribosomal RNA (28S rRNA) gene, and nuclear histone 3 (H3) gene of five tellinid species: two Pharaonella, two Tonganaella and one Tellinides species (Table
A list of bivalve species analyzed for genetic sequences of three genes (COI, 28S rRNA and H3).
Family | Species | Specimen | GenBank # | Locality | ||
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Catalogue # | COI | 28S rRNA | H3 | |||
Tellinidae | Macoma balthica | GenBank | KC429141 | KC429501 | KC429224 | |
Megangulus zyonoensis | GenBank | JX503037 | AB746875 | NA | ||
Moerella iridescens | GenBank | JN398362 | AB746876 | NA | ||
Pharaonella amanyu sp. n. | NSMT-Mo 78982 (holotype) | LC311753 | LC311747 | LC311757 | Edateku Is., Kagoshima, Japan | |
Pharaonella sieboldii | KUZ-Z1880 | NA | NA | LC311758 | Notojima, Ishikawa, Japan | |
Tellinella crucigera | GenBank | KC706878 | NA | NA | ||
Tellinella cumingii | KUZ-Z1881 | NA | LC311748 | LC311759 | Edateku Is., Kagoshima, Japan | |
Tellinella virgata | GenBank/ KUZ-Z1882 | AB741079 | LC311749 | LC311760 | Yohena, Okinawa, Japan | |
Scissula similis | GenBank | KC429142 | KC429502 | KC429225 | ||
Tellinides ovalis | KUZ-Z1883 | LC311754 | LC311750 | LC311761 | Yohena, Okinawa, Japan | |
Tonganaella perna | KUZ-Z1884 | LC311755 | LC311751 | LC311762 | Yohena, Okinawa, Japan | |
Tonganaella tongana | KUZ-Z1885 | LC311756 | LC311752 | LC311763 | Edateku Is., Kagoshima, Japan | |
Semelidae | Abra alba | GenBank | KT307619 | KF741656 | KC429228 |
The sequences were aligned using Muscle (
Bayesian and maximum likelihood (ML) phylogenetic analyses were performed based on the combined data set (28S + COI + H3) using MrBayes 3.1.2 (
Shell. Shell elongate, narrow, subequilateral; inequivalve; anterior section longer than posterior section (Fig.
Anatomy. Mantle and foot orange, thus similar to colour of shell (Fig.
Labial palps well developed in comparison with demibranchs. Outer and inner hemipalps elongate-triangular (Fig.
Holotype: NSMT-Mo 78982, paired valves, length 69 mm, height 32 mm (Figs
Edateku Island, Uken, Kagoshima Prefecture, Japan (28°17'26.08"N, 129°13'9.09"E); in sand of subtidal sand bank.
In addition to the type locality, the species has also been recorded at Kasari Bay on Amami-Oshima Island, but only by empty shells.
The epithet amanyu alludes to the mythical archaic peaceful era of Amami Islands, symbolising the undisturbed coastal ecosystem harbouring this bivalve species. It is used as a noun in apposition.
Aman’yu-beni-gai.
The bivalve was found deeply buried (about 15 cm) in subtidal sandy bottom.
For molecular phylogenetic analysis, COI, 28S rRNA, and H3 sequence data were compared for several Tonganaella and Pharaonella species (Table
Both morphological and molecular phylogenetic analyses suggest that the new species should be assigned to the genus Pharaonella. The morphological characteristic unique to Pharaonella is the commarginally grooved sculpture of right shell valves (
Although P. amanyu resembles Tonganaella species, it can be separated from T. perna by the orange colour of shells (white, yellowish or pinkish in T. perna) and the long anterior part of the shell (the posterior part is longer than the anterior part in T. perna), and from T. tongana by the orange colour of the shells and the absence of pink rays at the umbones (Table
Bivalve species | Shell narrowness (shell length/shell height) | Shell shape | Shell color | Sculpture of right valve | Pallial sinus | Distribution |
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Pharaonella aurea | narrowest (2.8–3.0) | anterior part longer than posterior part | bright red or rarely yellow | commarginally ridged | deep | from the Ryukyu Archipelago to Northern Australia |
P. dialeuca | narrow (2.4) | anterior part longer than posterior part | yellowish orange with two white umbonal divergent rays | commarginally ridged in posterior half | unknown | Philippine Islands |
P. sieboldii | very narrow (2.3–2.4) | anterior part longer than posterior part | pink | commarginally ridged | deep | around the Japanese Archipelago |
P. amanyu | narrow (2.1–2.2) | anterior part longer than posterior part | orange with many pale umbonal rays | commarginally ridged only in posterior beak | moderate | around Amami Islands |
Tonganaella perna | narrow (2.1–2.2) | anterior part shorter than posterior part | white or cream, rarely pink | smooth | moderate | from the Ryukyu Archipelago to Northern Australia |
T. tongana | least narrow (1.9–2.0) | anterior part as long as posterior part | white, sometimes reddish or yellowish, with pink rays only around unbones | smooth | moderate | from the Ryukyu Archipelago to Northern Australia |
It is remarkable that such a large bivalve living near the tidal zone has not been described until now. Among marine bivalves, there are several local endemic species confined to coastal ecosystems in the Ryukyu Archipelago: Gafrarium yukitai Habe, 1977 (Veneridae), Peregrinamor gastrochaenans Kato & Itani, 2000 (Galeommatidae), and Merisca monomera Habe, 1961, Semelangulus lacrimadugongi Kato & Ohsuga, 2007 (Tellinidae). The habitats of these endemic species are sandy or muddy tidal flats around estuaries, and the new species may provide another example of these endemic species confined to the Ryukyu Archipelago.
The type locality of the new species is the sand flat at Edateku Island, which is formed by clean white coarse sand lying along a narrow strait and harbours diverse characteristic sand-burrowing organisms such as sea cucumbers, spatangoid sea urchins, lancelets, fishes and molluscs such as terebrid, olivid, and naticid snails, and tellinids. It is noteworthy that one Pharaonella and two Tonganaella species should be recorded from the sand flat, because many of the tellinid bivalve species are now threatened in the Ryukyu Archipelago (
Sandy intertidal/subtidal flats and sandbanks form in inland seas along straits where tidal currents are strong (
The authors thank the Fisherman’s Union of Uken Village for permitting and helping us to study the marine fauna at the sand flat of Edateku Is., and Dr Richard C. Willan and Dr Lisa Kirkendale for their helpful comments on our manuscript. This research was supported in part by a Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (A) 2010–2014 (22247003, awarded to M. Kato).