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ISSN : 1226-9999(Print)
ISSN : 2287-7851(Online)
Korean J. Environ. Biol. Vol.37 No.4 pp.503-507
DOI : https://doi.org/10.11626/KJEB.2019.37.4.503

New record of a sea star of genus Solaster (Asteroidea: Valvatida: Solasteridae) from the East Sea, Korea

Michael Dadole Ubagan*, Sook Shin
Department of Animal Biotechnology & Resource, Marine Biological Resource Institute, Sahmyook University, Seoul 01795, Republic of Korea
Corresponding author Sook Shin Tel. 02-3399-1717 E-mail. shins@syu.ac.kr
23/09/2019 22/10/2019 23/10/2019

Abstract


Asteroid specimens were collected using fishing nets from the East Sea, Korea. The specimens were identified as Solaster paxillatus Sladen, 1889, belonging to the family Solasteridae of the order Valvatida. This species can be distinguished from three other Korean Solaster species by having 10 arms; subambulacral spines comprising four or five near base of arm, six or seven in middle part, and five or six in distal part of arm; furrow spines comprising four or five near basal part and three or four in distal part of arm; and suboral spines comprising more than ten spinules. The morphological characteristics of this species were described with illustrations. Solaster paxillatus is first reported in marine fauna of Korea.



초록


    Ministry of Environment
    NIBR201902107Ministry of Oceans and Fisheries
    20170431

    INTRODUCTION

    The family Solasteridae Viguier, 1878 comprises nine accepted genera (Crossaster Müller & Troschel, 1840; Heterozonias Fisher, 1910; Laetmaster Fisher, 1908; Lophaster Verrill, 1878; Paralophaster Fisher, 1940; RhipidasterSladen, 1889;Seriaster Jangoux, 1984; Solaster Forbes, 1839 and Xenorias Fisher, 1913), with 23 Solaster species (Mah 2019). Solasteridae is considered as a boreal family occurring in shallow to moderately deep waters (Downey 1971). Many solasterid species are multi-armed, with the enlarged central disc, but some have only five arms and have orange body color (Lambert 2000). Abactinal ossicles of solasterids are metapaxillae and they can be quite varied in a single specimen. The marginal series are paxilliform in most genera, and somewhat inconspicuous. Superomarginals are commonly quite small, but almost always at least slightly enlarged relative to adjacent abactinals (Fisher 1911). With the newly recorded species, Solaster paxillatus, in Korea, four species have been reported in Korean fauna. A key for Korean Solaster species was provided.

    MATERIALS AND METHODS

    Solaster specimens were collected using fishing nets from 8 Oct. 2009 to 10 Apr. 2019 from the East Sea (Daejin, Geojin, Mulchi, Donghae Daejin, Chogok) of Korea. The collected specimens were preserved in 95% ethanol, and morphological characteristics, such as the size of the disk, upper and proximal portions of the arms, number of abactinal spines, number of subambulacral spines, number of furrow spines, and number of oral and suboral spines were examined. We observed the external features of the specimens using a stereomicroscope. For observing the internal structures of the specimens such as the spines and the skeletal plates, sodium hypochlorite (5.25% solution) was applied carefully to dissolve the skin covering (Shin 2010). After complete removal of the skin, the skeletal parts and spines were washed with sufficient amounts of water and observed again using the stereo-microscope. The morphological features of the specimens were photographed using a scanning electron microscope (JSM-6510; JEOL Ltd., Tokyo Japan), stereomicroscope (Nikon SMZ1000; Nikon Co., Tokyo, Japan), and digital camera (Nikon D7000). Abbreviations for measurements follow Ubagan and Shin, 2019.

    SYSTEMATIC ACCOUNTS

    Class Asteroidea de Blainville, 1830

    Superorder Valvatacea Blake, 1987

    Order Valvatida Perrier, 1884

    Family Solasteridae Viguier, 1878

    Genus Solaster Forbes, 1839

    Key to the species of genus Solaster in Korea

    1. Arms 10 or more in number; paxillae on abactinal surface moderately large, not crowded; furrow spines three or more in proximal and distal portion of arm··························2

      • - Arms eight in number; paxillae on abactinal surface small, closely crowded; furrow spines two in proximal and one in distal portion of arm·········································Solaster endeca

    2. 2. Abactinal plates reticulated by three or more irregular plates; oral spines less than 10 in number, different from actinal spines·························································································3

      • - Abactinal plates imbricated by three to five irregular plates; oral spines more than 10 in number, similar from actinal spines·································································Solaster uchidai

    3. Inferomarginal plates bearing 20-25 spinules; ventro-interbrachial area narrow, crowded with paxillae comprising five to 12 web spinules; suboral spines comprising three or four spinules····························································Solaster dawsoni

      • - Inferomarginal plates bearing more than 30 spinules; ventro- interbrachial area wide, crowded with paxillae comprising seven to 18 web spinules; suboral spines comprising more than 10 spinules·································Solaster paxillatus

    1*Solaster paxillatusSladen, 1889 주황햇님불가사리 (신칭) (Figs. 1A-K, 2A-D)

    Solaster paxillatusSladen, 1889: p. 452, pl. 71, figs. 1-3, pl. 72, figs. 1-2;Fisher, 1911: p. 315, pl. 87, figs. 1-2, pl. 88, figs. 1-2, pl. 113, fig. 3; Hayashi, 1939: p. 303, pl. 24, figs. 5-6; Mah, 2019: 292727.

    Material examined. One specimen, Donghae Daejin, 08 Oct. 2009; two specimens, Mulchi, 17 Oct. 2010; one specimen, Geojin, 29 Aug. 2014; one specimen, Chogok, 19 Dec. 2014; two specimens, Daejin, 19 Aug. 2015; one specimen, Daejin, 10 Apr. 2019.

    Description. Arms 10 in number, long, slightly broad at base, tapering to tips; disk large, slightly elevated (Fig. 1A, B). Paxillae numerous, small, immersed in membrane, roundish (Figs. 1C, 2B) with small, slender 10-15 spinules (Fig. 2B). Abactinal skeleton irregularly reticulated with two or three lobed plates, covered by skin, situated midway between margin and center of disk. Papular areas containing five to ten or more papullae. Madreporite conspicuous with irregular striae, covered with some paxillae similar as abactinal paxillae (Fig. 1D). Marginal plates numerous, having two unequal series. Superomarginal plates smaller than inferomarginal plates, bearing 10 or more spinules slightly larger than adjacent abactinal paxillae. Inferomarginal plates large, numerous, forming paxilliform, bearing numerous spinules, inner part larger than outer end, forming two or three series, longer than superomarginal plates (Fig. 1F). Ventro-interbrachial area large, crowded with paxillae bearing seven to 18 web spinules (Fig. 2C), some paxillae forming fan-like shape and extending about one fourth length of arm (Fig. 1G). Furrow spines long, slender, comprising four to five near base of arm, and three to four in distal part of arm (Fig. 1H). Subambulacral spines comprising four to five near base of arm, six to seven in middle part, and five to six in distal part of arm (Fig. 1I-K). Oral plate broad, bearing nine or 10 bluntly pointed spines, inner three slightly longer and larger than subambulacral spines, middle spines larger than adjacent spines and forming elongated triangular shape. Suboral spines more than 10 in number, inner spines longer than outer spines (Figs. 1E, 2D).

    Size. R=145-225 mm, r=46-70 mm, R/r=3.1-3.2.

    Distribution. Korea (East Sea), Japan (Honshu, south of Yeddo, Yokohama), Alaska (Kadiak Island).

    Deposition. The collected specimens were deposited in the Marine Echinoderm Resource Bank of Korea (MERBK), Sahmyook University, Seoul, Korea.

    Remarks.Solaster paxillatus had been first described by Sladen (1889) from south of Yeddo, Japan. The morphological characteristics of our specimens agree with the morphological description of Sladen (e.g. arm to disk ratio, disk size, shape of abactinal paxillae, size of superomarginal plates, and number of oral spines). Some slight differences such as the number of arms, number of subambulacral spines, and arrangement of furrow spines were observed (Table 1).

    Our specimens can be distinguished from previously reported Solaster species in Korea such as S. dawsoni and S. uchidai by (1) the ventro-interbrachial area, S. paxillatus having wide ventro-interbrachial area with fan-shaped paxilliform (Fig. 1G), while S. dawsoni and S. uchidai has narrow ventro-interbrachial area; (2) the number of suboral spines, S. paxillatus has 11 or 12 spines, while S. dawsoni has three or four, and S. uchidai containing one to five spines. The wide ventro-interbrachial area of S. paxillatus is nearly similar to S. endeca, but differs by the series of paxillae extending about middle of the arm in S. endeca, while in S. paxillatus, the series of paxillae just extending one fourth length of arm. Solaster paxillatus is first reported in Korean fauna.

    ACKNOWLEDGEMENT

    This study was supported by a grant from the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) (NIBR201902107), and the Marine Biotechnology Program of the Korea Institute of Marine Science and Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries (MOF) (No. 20170431), and it was a part of the project titled “Development of the methods for controlling and managing marine ecological disturbance-causing and harmful organisms (MEDHO),” funded by the Ministry of Oceans and Fisheries, Korea.

    Figure

    KJEB-37-4-503_F1.gif

    Solaster paxillatus. A. abactinal side, B. actinal side, C. abactinal paxillae, D. madreporite, paxillae, E. oral spines, F. inferomarginal spines, G. ventro-interbrachial area, H. furrow spines (proximal part), I-K. subambulacral spines (I. proximal part, J. middle part, K. distal part). Scale bars: A, B=3 cm, C-K=1 mm.

    KJEB-37-4-503_F2.gif

    Solaster paxillatus, paxillae and spines, SEM images. A. abactinal paxillae, B. abactinal spines, C. ventro-interbrachial spines, D. sub - oral spines. Scale bars: A, D=500 μm; B, C=200 μm.

    Table

    Comparison of morphological characteristics of Solaster paxillatus used in this study and original type material

    Reference

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    3. Hayashi R. 1939. Solasterids in Japanese waters. J. Fac. Sci. Hokkaido Imp. Univ. 6:297-311.
    4. Lambert P. 2000. Sea Stars of British Columbia, Southeast Alaska, and Puget Sound. Royal British Columbia Museum. pp. 1-186.
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