Research Article |
Corresponding author: Asako K. Matsumoto ( amatsu@gorgonian.jp ) Academic editor: Bert W. Hoeksema
© 2016 Asako K. Matsumoto, Leen P. van Ofwegen.
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:
Matsumoto AK, van Ofwegen LP (2016) Species of Elasmogorgia and Euplexaura (Cnidaria, Octocorallia) from Japan with a discussion about the genus Filigella. ZooKeys 589: 1-21. https://doi.org/10.3897/zookeys.589.8361
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Octocorals with thread-like colony shape have been re-examined, mainly from Japanese waters. The holotypes of Elasmogorgia filiformis and Filigella boninensis and a syntype of F. mitsukurii have been studied. Euplexaura arbuscula is identified and Euplexaura yayoii sp. n. described.
Astrogorgia , Thesea , Plexauridae , Alcyonacea , deep-water octocorals, Indo-Pacific, new species, Challenger Expedition
The octocoral genera Elasmogorgia, Filigella and Thesea have been underexplored and their taxonomic position remains confusing. One of the Japanese species of these genera, Filigella mitsukurii, is classified with three different genera in WoRMS, as Elasmogorgia mitsukurii (
The genus Filigella Gray, 1868 was established to accommodate F. gracilis from Brazil. Later on Wright and Studer (1899) established the Pacific genus Elasmogorgia with the remark that their new species E. filiformis could be identical to Filigella gracilis. Next,
In the present study, the type material of Elasmogorgia filiformis, E. filigella, Filigella mitsukurii, and F. boninensis, is examined and their previous identifications are discussed. In addition, two specimens identified as E. filiformis by
Finally, a new thread-like Euplexaura species is decribed from the Pacific side of northern Japan, Euplexaura yayoii sp. n., in addition to E. arbuscula Broch, 1935 from off Chishima Is. (Kuril Is.), which previously was reported from the west coast of Kamchatka, Sea of Okhotsk. These two species are both from northern Japan and northeastern Russia (Figure
BMNH
British
NBC (
Material was collected from depths between 38 and 366 m by dredging, trawling or fishing net onboard RV Tansei-maru, University of Tokyo and Japan Agency for Marine-earth Science and Technology and RV Yayoi, the University of Tokyo, during the years 1975–2010. Type specimens and other historical museum material was examined in collections of the BMNH, NBC,
From each specimen a small piece of the distal part of a branch was dissolved in a solution of household bleach (4% hypochlorite) to isolate sclerites. The sclerites were washed with demineralised water, dried on a hot plate, mounted on SEM stubs, and coated with Pd/Au for SEM imaging. For this, either a JEOL JSM6490LV scanning electron microscope was operated at high vacuum at 10 kV, or a JEOL JSM6510LA scanning electron microscope with a Quick Carbon Coater SC-701C, SANYU ELECTRON was used. For terminology, see
Descriptions of old Japanese material collected by Japanese used “hiro” (Japanese fathom) as the depth unit. One Japanese fathom (hiro) is usually 1.43 m, occasionally 1.51 m, whereas, it is 1.818 m for the length unit on land. The old depth unit fathom is also converted to 1.8288 m. When it was not clear whether the collector used fathom or hiro, the converted depth has wider ranges.
Elasma (non Elasma Jaennicke 1866); Studer (and P. Wright) 1887: 58.
Elasmogorgia Wright & Studer, 1899: 132;
?Elasmogorgia;
NOT Elasmogorgia;
Partly Elasmogorgia;
Plexauridae with sparsely branched colonies lacking a holdfast. Calyces dome-shaped. Polyps with collaret and points. Sclerites are colourless spindles.
Elasmogorgia filiformis Wright & Studer, 1889: 133 (Indonesia, Arafura Sea);
?Elasmogorgia filiformis;
NOT Elasmogorgia filiformis;
Holotype BMNH 1889.5.27.77, Arafura Sea, South of Papua, 28 fms, Challenger st. 188, 10 September 1874;
Colony thread-like (Figure
One somewhat flattened spindle was found, 0.35 mm long, maybe referable to a collaret (Figure
Euplexaura Verrill, 1869: 75;
Plexauridae with colonies branched in one plane. Calyces may be present but are mostly absent. Polyps with collaret and points, only point sclerites, or no sclerites at all. The surface of the coenenchyme with robust ovals or spindles with complex tubercles; sometimes with one side that is less tuberculate. The interior with rods or small spindles with simple tubercles. All sclerites colourless.
Euplexaura arbuscula Broch, 1935: 20, fig. 12.
Branches thread-like. Calyces dome-shaped, arranged all around the branches (Figure
The material examined was fragmentary (Figure
Euplexaura abietina Kukenthal, 1909 resembles E. arbuscula regarding its sclerites, but it differs in having polyp spindles.
Since its original description, the species was not found again and its type material could not be retraced, hence some doubts remain about the identification of this species.
Kamchatka, Sea of Okhotsk, off Chishima Is. (= Kuril Is.).
Filigella boninensis Aurivillius, 1931: 139 (Bonin Islands).
Thesea boninensis;
Holotype UPSZTY2165 (
Branches thread-like, 6 cm in length. Calyces dome-shaped, arranged all around the branches (Figure
The surface layer of the coenenchyme has spindles (Figure
Because the sclerites of this species are spindles and ellipsoids with complex tubercles it actually represents an Euplexaura species. It is the only species of Euplexaura with thread-like colony shape which has many sclerites with one side that is less tuberculate.
Filigella mitsukurii Kinoshita, 1909: 1(Sagami Bay);
Elasmogorgia mitsukurii;
Thesea mitsukurii;
Thesea sp.
Syntypes
Branches thread-like. The examined syntype has two branches arising from the main stem with a length of 19 cm and 28.5 cm, respectively; the main stem is 9 cm long. Calyces dome-shaped, arranged all around the branches (Figure
The surface layer of the coenenchyme has spindles (Figure
Because the sclerites of this species are spindles with complex tubercles this is actually a species of Euplexaura.
The locality name “Jogaschima, Pagamibai” of this species in
Sagami Bay, off Boso Peninsula, Kashima Sea, Suruga Bay, Bungo Channel, East China Sea, Japan.
Holotype
The holotype is 2.5 cm high and 5.5 cm wide (Figure
The polyps have points with slightly bent, flattened spindles, up to 0.30 mm long, with a few tubercles and a slightly spiny distal end (Figure
Named after the research vessel that was used to collect the specimens.
The live colony has blue-coloured polyps. E. yayoii differs from the two other Japanese Euplexaura species with thread-like branches, E. boninensis and E. mitsukurii, by its very small sclerites.
Otsuchi Bay, Iwate Prefecture, Japan.
Originally, there were four species of Elasmogorgia: E. filiformis Wright & Studer, 1889, E. filigella
All Japanese thread-like plexaurid material South of Kashima Sea was previously identified as F. mitsukurii and it clearly is the most common thread-like plexaurid species of Japan.
We thank the following persons for allowing us to examine material and for hosting: Ms. Miranda Lowe and Mr. Andrew Cabrinovic, BMNH, London, UK; Dr. Rei Ueshima,