A New Record of Brittle Star Ophiopsila Cf. Polyacantha (Echinodermata: Ophiuroidea) from Southwestern Japan, with Notes on Its Bioluminescence

Species Diversity 25: 283–294 Published online 28 October 2020 DOI: 10.12782/specdiv.25.283

A New Record of Brittle Star Ophiopsila cf. polyacantha (Echinodermata: Ophiuroidea) from Southwestern Japan, with Notes on its Bioluminescence

Masanori Okanishi1,3 and Takuma Fujii2 1 Misaki Marine Biological Station, Department of Science, The University of Tokyo, 1024 Koajiro, Miura, Kanagawa 238-0225, Japan E-mail: [email protected] 2 International Center for Island Studies, Kagoshima University, 15-1-6F Naze-Minatomachi, Amami, Kagoshima 894-0026, Japan 3 Corresponding author (Received 26 May 2020; Accepted 23 July 2020)

Two specimens of Ophiopsila cf. polyacantha H. L. Clark, 1915 are described from approximately 15 m water depth at Kakeromajima island, Amami Islands in southwestern Japan. The species occurs on sandy bottoms with the disc buried and the arms extended above the substratum. Bioluminescence and burrowing behavior are described. The specimens are clearly morphologically different from the two species of Ophiopsila Forbes, 1843 previously recorded from Japan. The new Japanese name “Kin-habu-toranoo-kumohitode” is proposed. Key Words: brittle star, scuba diving, bioluminescence, Amami islands, Pacific Ocean.

these, only O. pantherina Koehler, 1898 and O. squamifera Introduction Murakami, 1963 have been reported from Japanese waters (Okanishi 2016). Recently, Okanishi et al. (2019) described Recent investigations by SCUBA diving have revealed O. xmasilluminans Okanishi, Oba, and Fujita, 2019 from a many undescribed benthic invertebrate species from the submarine cave in northwestern Australia, with notes on its subtidal zone, usually in depths greater than 10 m, espe- bioluminescence and its sand-burrowing behavior. Howev- cially in the Ryukyu Islands, southwestern Japan (e.g., Kise er, other species with this combination of ecological propen- et al. 2017; Naruse and Yoshida 2018). In this area, many sities have not yet been described from this genus. new records and species of marine benthos from depths Recent descriptions of ophiuroids have included a com- of 15–40 m have recently been described (e.g., Obuchi et prehensive range of photographs and/or drawings of rel- al. 2009; White and Reimer 2012; Fujii and Reimer 2016; evant diagnostic morphological characters as well as scan- Lau et al. 2019). In contrast, benthic fauna of the Amami- ning electron microscope (SEM) images of ossicles, which oshima island which is the second-biggest island within the provide a consistent suite of characters for comparison and Ryukyu Islands, and neighboring Kakeromajima, Ukejima identification (e.g., Martynov 2010; Thuy and Stöhr 2016; and Yorojima islands (in this study, these four islands are Okanishi and Fujita 2018a). Compilation of such data for referred “Amami-oshima island group”; Fig. 1), has been Ophiopsila has only recently begun (e.g., Okanishi et al. poorly studied (e.g., Toyama 2014; Nakae et al. 2018; Reimer 2019). Here, we present detailed photographs of all relevant et al. 2019). Amami-oshima island lies in the northernmost parts of the body for the new recorded species of Ophiopsila area of well-developed coral reefs. The sandy substratum cf. polyacantha H. L. Clark, 1915 from Japan. Additionally, adjacent to the coral reef forms a sheltered bay. Faunistic based on in situ observations, we provide photographs of studies in this area are important for gaining a better un- life color, and brief descriptions of bioluminescence and the derstanding of the marine biodiversity, as it lies within the sand-burrowing behavior of this species. northernmost region of tropical marine ecosystem in Japan. Ophiuroids (Echinodermata) contain the largest number of species within the phylum Echinodermata and they in- Materials and Methods habit nearly all marine habitats (Stöhr et al. 2012; Okanishi 2016). Although some ophiuroid species have been reported Two specimens of Ophiopsila cf. polyacantha were collect- from offshore areas of the Amami-oshima island group (e.g., ed and observed in situ by the second author (TF) during Okanishi and Fujita 2009), the subtidal zone has been barely SCUBA diving at Kedomi, Ikomo Bay, central Kakeroma- explored. jima island, on the southern side of Amami-oshima island, Originally a monotypic genus Ophiopsila Forbes, 1843 Kagoshima [28.097783N, 129.241322E (decimal scale)], (Ophintegrida: Amphilepidida: Ophiopsilidae) currently southwestern Japan, at 15 m depth, on 26 September 2019 comprises 28 nominal species (Okanishi et al. 2019). Of and at 16.7 m depth, on 4 February 2020 (Fig. 1).

Christodoulou et al. (2019).

Taxonomy

Class Ophiuroidea Gray, 1840 Superorder Ophintegrida O’Hara, Hugall, Thuy, Stöhr, and Martynov, 2017 Order Amphilepidida O’Hara, Hugall, Thuy, Stöhr, and Martynov, 2017 Suborder Ophiopsilina Matsumoto, 1915 Superfamily Ophiopsiloidea Matsumoto, 1915 Family Ophiopsilidae Matsumoto, 1915 Genus Ophiopsila Forbes, 1843 [New standard Japanese genus name: Toranoo-kumohitode- zoku] Ophiopsila cf. polyacantha H. L. Clark, 1915 [New standard Japanese name: Kin-habu-toranoo-kumo hitode] (Figs 2–8)

Ophiopsila polyacantha H. L. Clark, 1915: 297, 298, pl. 14, figs 6, 7; H. L. Clark 1918: 329; Koehler 1930: 209.

Material examined. NSMT E-13189: one specimen, Ke- domi, Kakeromajima island, Amami-oshima island, Kago shima Prefecture, southwestern Japan, depth approximately 15 m, SCUBA diving, collected by T. Fujii, 26 Septem- ber 2019. NSMT E-13190: one specimen, same locality as NSMT E-13189, 16.7 m, 4 February 2020. Fig. 1. Sampling location of Ophiopsila cf. polyacantha (star sym- Diagnosis. Disc surface entirely covered by thick skin; bol). two flat oral papillae s.l.; oral shields oval, longer than wide; dorsal arm plates hexagonal in proximal portion of arms; A single specimen (NSMT E-13189) was anaesthetized in arm spines long and flat, no more than 11 in number on a 10% aqueous solution of magnesium chloride, then fixed proximal portion of arm; adradial tentacle scale narrow and in 99% ethanol. Another single specimen (NSMT E-13190) long; arms approximately 18 times longer than disc diam- was directly immersed in 99% ethanol without anesthetiza- eter; vertebrae with perforation on distal portion of arm. tion. Photographs were taken during anaesthetisation to Description of external morphology (NSMT E-13189). prevent long arms from winding vertically, and fixation of Disc. Circular, 14.3 mm in diameter (Figs 2C–F, 3A), surfac- NSMT E-13189. An arm of NSMT E-13189 was dissected es completely covered by thick skin, and no external ossicles to remove internal ossicles using domestic bleach (ap- observed even when dried (Fig. 3A–C). Radial shields and proximately 5% sodium hypochlorite solution), washed in their surrounds slightly tumid, bar-like, 6 to 7 times longer deionised water, dried in air and mounted on SEM stubs than wide, one third to half disc radius (Fig. 3C). On ven- using double-sided conductive tape. The preparations were tral surface, oral shields, adoral shields and oral plates com- sputter-coated with gold-palladium, examined and photo- pletely covered by the thick skin (Fig. 3D). Oral shield serv- graphed with a Jeol JSM 5510LV SEM of the Misaki Marine ing as madreporite unrecognizable in external view (Fig. Biological Station of The University of Tokyo (MMBS). Both 3D). Interradial ventral disc covered also by skin (Fig. 3E). specimens were deposited in the National Museum of Na- Genital slits long, almost extending to dorsal disc edge (Fig. ture and Science (NSMT). Morphological terminology used 3E, F), approximately 0.27 mm in width (Fig. 3E). Two flat, in this study follows Stöhr et al. (2012), Okanishi and Fujita subequal presumably infradental papillae and adoral shield (2018b), and Hendler (2018). Terminologies of oral papillae spines and a spiniform oral plate ridge papilla just below the were used as sensu lato (hereafter s.l.) in Hendler (2018) and inner presumably infradental papilla at each opening for were mainly determined based on ontogenetic and anatomi- the second tentacle of adoral shield (Fig. 3D). More than 20 cal observations. In this study, we did not observe any on- pointed tooth papillae on dental plate, forming 3 or 4 verti- togenetic series and did not dissect mouth ossicles to pre- cal rows (Fig. 3D). Second tentacle pore completely inside vent destruction of discs of the specimens. Thus, we marked the mouth slit. “?” for these ossicles which we are not sure (Fig. 3D). Sys- Arms. Five, approximately 255 mm long, approximately tematics used in this study follows O’Hara et al. (2018) and 3.3 mm wide and 3.4 mm high in proximal portion, square New record of Ophiopsila cf. polyacantha from Japan 285

Fig. 2. Ophiopsila cf. polyacantha, living, in situ (A, B), anesthetized (C, D) and fixed (E–H) states of a smaller specimen (A, G, H; NSMT E-13190) and a larger specimen (B–F; NSMT E-13189). A, with burrowed disc and extended arms; B, exposed from sand ground, dorsal view; C, E, G, dorsal views; D, F, H, ventral views. Scale bars=1 cm. in cross section. Arms gradually tapering distally (Fig. 2C, External shape of lateral arm plates mostly concealed by D). arm spines, separated by dorsal and ventral arm plates On proximal to middle portion of the arms, ventral arm (Figs 3F, G, 4A, B; see detailed morphological description plates slightly wider than long, distal and proximal sides below). On distal portion of arms, ventral arm plates long, straight and both lateral sides concave, contiguous (Figs 3F, concave on both lateral and distal sides, convex on proximal G, 8M–P). Dorsal arm plates oblong, slightly wider than side (Figs 4H, 8Q, R). Dorsal arm plates longer than wide, long, distal edge slightly rounded, contiguous (Fig. 8G–J). oval, and pointed proximally (Figs 4C, 8K, L). Lateral arm 286 M. Okanishi and T. Fujii

Fig. 3. Ophiopsila cf. polyacantha (NSMT E-13189): A, dorsal disc; B, dorsal central part of disc; C, dorsal peripheral part of disc, arrowheads indicate internal edges of radial shields; D, jaws; E, lateral interradial part of disc; F–H, oral views of arms, proximal (F), middle (G) and distal (H) portions. Abbreviations: AdS, adradial shield; AS, arm spine; ASS, adoral shield spine; GS, genital slit; IP, infradental papilla; OS, oral shield; ORS, oral ridge spine; TS, tentacle scale; VAP, ventral arm plate. Scale bars=1 mm. plates bearing arm spines; on proximal portion of arm, 11 half the length of corresponding arm segment (Figs 3G, 4B, long, flat and broad spines, dorsal- and ventral-most spines E). On distal portion of arms, two spiniform arm spines, the longest, approximately 1.5 to 2 times longer than cor- ventral-most spine longest, almost same length as corre- responding arm segment, third from ventral-most spines sponding arm segment and dorsal-most spine half length shortest, slightly shorter than the corresponding arm seg- of corresponding arm segment (Figs 3H, 4C, F). Tentacles ment (Figs 3F, 4A, D). On middle portion, 5 or 6 spines, long, approximately 3 to 4 times longer than correspond- long and flat, ventral-most spine longest, approximately 1.5 ing arm segment, with fine protrusions arranged in multiple times longer than the corresponding arm segment, spine longitudinal lines (Fig. 4F). Tentacle scales two, adradial one length gradually decreasing towards dorsal side, exceeding longer, thin, spiniform and covered by skin, approximately New record of Ophiopsila cf. polyacantha from Japan 287

Fig. 4. Ophiopsila cf. polyacantha (NSMT E-13189): A–C, dorsal views of arms, proximal (A), middle (B) and distal (C) portions; D–F, lateral views of arms, proximal (D), middle (E) and distal (F) portions. Arrows indicate orientations: do, dorsal side; v, ventral side. Arrowheads indicate arm spines. Abbreviations: DAP, dorsal arm plate; T, tentacle; TS, tentacle scale. Scale bars=1 mm. twice as long as corresponding arm segment on proximal sion, and strongly pointed on ventral-distal side (Fig. 7B, C). portion of arm and approximately same length of the corre- On inner surface, irregular series of perforations forming a sponding arm segment on middle to distal arm (Fig. 3F–H); vertical line on the center (Fig. 7C) and two well defined, outer tentacle scale shorter, flat and broad, approximately confluent knobs lying on ventral side (Fig. 7C). Six to seven half the length of corresponding arm segment on proximal equal-sized spine articulations on distal edge (Fig. 7B, D), portion of arm with length decreasing to one-quarter of the composed of parallel, horizontal and equal-sized dorsal and length of corresponding arm segment distally (Fig. 3F–H). ventral lobes, with muscle and nerve openings inside lobes Detailed descriptions of ossicles are provided below. (Fig. 7D). A short ridge in proximal space between a pair Description of ossicle morphology (NSMT E-13189). of lobes (Fig. 7B). In middle portion of arm, proximal edge Vertebrae with zygospondylus articulation, large dorsal and straight and distal edge rounded; positions of three spine ar- ventral muscle flanges on both distal and proximal sides ticulations, confluent knobs and ridges almost same as those (Figs 5A, B, F, G, 6D, E). Surfaces of lateral saddle smooth, of proximal portion of arm but perforations unrecognizable with no special ornamentation (Figs 5D, E, 6B, C). On prox- (Fig. 7E–G). Spine articulations on distal edge (Fig. 7E, G), imal side, dorsal muscle flanges wider than ventral muscle composed of parallel, horizontal and equal-sized dorsal and flanges in proximal and middle portion of arm and on dis- ventral lobes, with muscle and nerve openings inside lobes tal portion of arm, ventral muscle flanges slightly narrower (Fig. 7G). Distal lateral arm plates elongated parallelograms than dorsal muscle flanges (Figs 5B, G, 6D), and on distal with slightly pointed ventral-proximal and dorsal-proximal side, width of both muscle flanges almost the same (Figs 5A, protrusions (Fig. 7I). On inner surface, a perforation recog- F, 6E). Longitudinal deep furrows on both dorsal and ven- nizable centrally, no conspicuous ridge defined (Fig. 7H). tral sides (Figs 5C, D, 6A, B, 7F, G). Transverse furrow on Two equal-sized spine articulations on distal edge (Fig. 7J), proximal portion of the arm (Fig. 5D). Channels for passag- composed of parallel, horizontal and equal-sized dorsal and es of lateral canals unrecognizable on ventral furrow (Figs ventral lobes, muscle and nerve openings unrecognizable 5C, 6A, F). Depression for tentacles located on lateral distal (Fig. 7J). Arm spines long, flat and broad on proximal por- side of the vertebra (Figs 5C, E, 6A, C, 7A). tion of arm (Fig. 7K, L). In middle arm portions, the middle Proximal lateral arm plates (slightly distant from the base spine cylindrical, while other ventral and dorsal spines still of the arm) higher than long, strongly arched, sickle-shaped, flat and broad (Fig. 8A, B); spines on distal portion of arm, with pointed ventral-proximal and dorsal-proximal protru- spiniform (Fig. 8C). Adradial tentacle scales long, flat, thin, 288 M. Okanishi and T. Fujii

Fig. 5. Ophiopsila cf. polyacantha (NSMT E-13189), SEM photographs of vertebrae from proximal (A–E) and middle (F, G) portions of arms. A, F, distal views; B, G, proximal views; C, ventral view; D, dorsal view; E, lateral view. Arrowheads indicate orientation: do, dorsal side; dis, distal side; pro, proximal side; v, ventral side. Abbreviations: DF, dorsal muscle flange; DT, depression for tentacle; LaS, lateral saddle; LoF, longitudinal furrow; TrF, transverse furrow; VF, ventral muscle flange. Scale bars=100 µm. and gradually decreasing in size from proximal to distal dorsal arm plates also hexagonal but the lateral side acute, (Fig. 8D–F) arm regions, abradial scales shorter and flatter density of stereom almost the same on both dorsal and than inner. ventral sides (Fig. 8H, I). On distal portion of arm, dorsal Proximal dorsal arm plates hexagonal, as long as wide, arm plate rhomboid with rounded edge, longer than wide, distal edge becoming rounder, and density of stereom struc- pointing to proximal edge, similar in form to a water drop, ture coarser dorsally than ventrally (Fig. 8G, H). Middle density of stereom almost the same in dorsal and ven- New record of Ophiopsila cf. polyacantha from Japan 289

Fig. 6. Ophiopsila cf. polyacantha (NSMT E-13189), SEM photographs of vertebrae from middle (A–C) and distal (D–G) portions of arms. A, F, ventral views; B, G, dorsal views; C, lateral view; D, proximal view; E, distal view. Arrowheads indicate orientation: do, dorsal side; dis, distal side; pro, proximal side; v, ventral side. Abbreviations: DF, dorsal muscle flange; DT, depression for tentacle; H, hole; LaS, lateral saddle; LoF, longitudinal furrow; VF, ventral muscle flange. Scale bars=100 µm. tral sides (Fig. 8K, L). Ventral arm plates on proximal and Color. In life, the anesthesia did not change the color (Fig. middle portion of arm octagonal, spearhead-shaped, wider 2A–D). Dorsal periphery of disc and radial shields generally than long, with concave lateral edges (Fig. 8M–P), becom- pale grey, with patchy patterns of dark brown and yellow ing spear shaped distally, pointing to distal side, with con- (Figs 2C, 3A). Arms basically pearl white, with yellow trans- cave lateral edges (Fig. 8Q, R). Density of stereom structure verse bands, that are 2 arm segments in thickness, separated coarser on dorsal side than ventral side (Fig. 8M–R). by 2 to 5 arm segments in an irregular sequence (Figs 2, 4). 290 M. Okanishi and T. Fujii

Fig. 7. Ophiopsila cf. polyacantha (NSMT E-13189), SEM photographs of arm ossicles from distal portion (A, H–J), proximal portion (B–D, K, L) and middle portion (E–G): A, vertebra, lateral view; B–J, lateral arm plates, external views (B, E, H), internal views, arrowheads indicate perforations (C, F, I) and distal views (D, G, J); K, L, arm spines, ventral most (K) and middle (L) one. Arrowheads indicate orientations: ba, basal side; dis, distal side; do, dorsal side, ex, external side; v, ventral side; pro, proximal side. Abbreviations: DL, dorsal lobe; DT, depression for tentacle; K, knob; MO, muscle opening; NO, nerve opening; R, ridge; TN, tentacle notch; VL, ventral lobe. Scale bars=100 µm.

Additionally, the yellow bands are flanked both proximally proximally, and brown transverse bands more distally (Figs and distally by brown transverse bands that are 1 arm seg- 2, 3G, H, 4). Ventral disc creamy white with patchy pat- ment in thickness. Between the brown bands, there are arm terns of dark brown on oral frames and annular dark brown segments of varying brown pigmentation giving the ap- bands on ventral arms like those on dorsal side (Figs 2D, pearance of brown longitudinal and transverse bands more 3D–H). The living color of arm tips of the smaller specimen New record of Ophiopsila cf. polyacantha from Japan 291

Fig. 8. Ophiopsila cf. polyacantha (NSMT E-13189), SEM photographs of arm ossicles: A–C, arm spines from middle (A, B) and distal (C) portion of arms, ventral most (A, C) and middle (B) one; D–F, adradial tentacle scales, from proximal (D), middle (E) and distal (F) portion of arms; G–L, dorsal arm plate from proximal (G, H), middle (I, J) and distal (K, L) portion of arms, internal (G, J, L) and external (H, I, K) views; M–R, ventral arm plates from proximal (M, N), middle (O, P) and distal (Q, R) portion of arms, internal (M, O, Q) and external (N, P, R) views. Arrowheads indicate orientations: ba, basal side; dis, distal side; ex, external side; pro, proximal side. Scale bars=100 µm.

(NSMT E-13190) is almost the same as the larger specimen as in its living state (Fig. 2E, F). In the fixed state, however, (Fig. 2A; NSMT E-13189). But color of the remaining area proximal-dorsal portion of arms are dark brown, except for of the smaller specimen is unknown. the yellow bands. A specimen fixed in ethanol for approximately 6 months Variation. Some morphological variation was observed (NSMT E-13189) displays almost the same color pattern in the two examined specimens. The larger specimen 292 M. Okanishi and T. Fujii

[NSMT E-13189: disc diameter (d.d.)=14.3 mm] has up to tha, because of the issues, for example of not having DNA 11 arm spines on the proximal portion of the arm, whereas analysis done, still to be addressed. the smaller specimen (NSMT E-13190: d.d.=7.0 mm) has Some species of the genus Ophiopsila, O. brevisquama up to 7 arm spines. Of these arm spines on each lateral arm Koehler, 1930, O. multipapillata Guille and Jangoux, 1978, plates, the longest spines are the dorsal- and ventral-most in O. novaezealandiae Baker, 1974; O. guineensis Koehler, 1930, the larger specimen, while in the smaller specimen, the ven- O. platispina Koehler, 1930 and O. seminuda A. M. Clark, tral-most arm spine is the longest but the length decreases 1952 are resemble to our examined specimens in having toward the dorsal side. arm spines which are all flat on proximal portion of the arm. Distribution. Ophiopsila polyacantha is known from The examined two specimens differs in (1) the covering of the Strait of Macassar, Borneo Bank, Indonesia, approxi- the disc, (2) number and shape of oral papillae s.l., (3) shape mately 60 m depth (type locality; H. L. Clark 1915); Singa- of dorsal arm plate on the proximal portion of the arms, (4) pore (Koehler 1930); Kedomi, central Kakeromajima island, shape of adradial tentacle scales (Koehler 1930; A. M. Clark Amami-oshima island group, Kagoshima Prefecture, south- 1952; Baker 1974; Guille and Jangoux 1978) as follows: western Japan, approximately 15 m depth (this study). (1) Disc covering: Disc of our examined specimens are Habitat. Both specimens (NSMT E-13189 and NSMT covered only by thick skin. Those of O. novaezealandiae, E-13190) of Ophiopsila cf. polyacantha were collected in O. seminuda, O. guineensis and O. platispina are covered by sandy bottoms, with buried disc and arms extended and scales, and that of O. brevisquama is covered by small gran- strongly waving into the water column at night time (Fig. ules. The disc of the holotype of O. multipapillata was cast 2A, B). off and no additional specimens of this species have been Remarks. The examined species falls within the genus recorded. Ophiopsila by virtue of having extremely long tentacle scales (2) Oral papillae s.l.: On each side of the ventral edge of that cross on the mid-line of the ventral side of arm; arm oral plate, two oral papillae s.l. (not including oral ridge spine articulations of lateral arm plates with two smooth, spine) are present in our examined specimens, O. brevisqua- parallel, straight lobes; a short ridge in proximal space be- ma, O. guineensis, O. seminuda and O. platispina. In con- tween the lobes; inner side of the lateral arm plates with trast, there are 6 or 7 oral papillae s.l. in O. multipapillata, two merged knobs (Guille and Jangoux 1978; O’Hara et al. and 3 to 5 in O. novaezealandiae. 2018). (3) Dorsal arm plate: Hexagonal in our examined speci- The morphology of our examined specimens, in particu- mens and O. quineensis, square in O. platispina, O. multipa- lar, their characteristic coloration is almost identical to that pillata and O. brevisquama, and oblong (longitudinally long) of O. polyacantha from Indonesia. in O. novazealandiae and O. seminuda. Since the coloration has often been considered an im- (4) Tentacle scales: Adradial tentacle scales of our ex- portant diagnostic character in the taxonomy of ophiuroids amined specimens, O. brevisquama, O. multipapillata, O. (e.g., A. M. Clark and Rowe 1971; Irimura and Yoshino novaezealandiae, and O. seminuda are narrow, cylindrical 1999), our examined specimens should be closely compared and long. On the other hand, they are long and flat in O. to O. polyacantha. There is a difference in the number of guineensis, and short and broad in O. platispina. arm spines between O. polyacantha and our examined speci- Length of arm of O. cf. polyacantha exceeds approxi- mens when comparing individuals of the same size: 11 in O. mately 18 times disc diameter, a feature also of O. xmasil- polyacantha (d.d.=7.0 mm), while 7 in our examined speci- luminans. However, the oral shields, dorsal arm plates and men (d.d.=7.0 mm; NSMT E-13190). However, the larger ventral arm plates on proximal portion of arms are oval, specimen we examined has 11 arm spines (d.d.=14.3 mm; hexagonal and octagonal in O. cf. polyacantha. In contrast, NSMT E-13189). This suggests that for the genus Ophiop- these are diamond-shaped, square and oblong, laterally con- sila at least for our examined specimens, the number of arm cave, in O. xmasilluminans. Additionally, O. cf. polyacantha spines, which has historically been utilized important for possess continuous holes on vertebrae on distal portion of taxonomy of Ophiopsila, varies with growth. Thus the stabil- arms, but these are absent in O. xmasilluminans. O. cf. poly- ity of this character should be carefully examined, while also acantha has black and yellow conspicuous spots and alter- collecting data on variation in other species. This also raises nating bands on disc and arms (Fig. 2), but O. xmasillumi- the possibility that our examined specimens are one varia- nans has yellow concentric bands and green band on disc tion form of O. polyacantha and should be identified as this and arms (Okanishi et al. 2019). species. We obtained only two individuals in this study and the The original description of O. polyacantha was detailed comparative data of Ophiopsila for DNA analysis were not (H. L. Clark 1915), so the morphological comparison could available on GenBank. Therefore, in order to clarify the tax- be made as described above, but the type locality of O. poly- onomy of the O. cf. polyacantha and allied species, further acantha, Indonesia, is more than 4,000 km away from Japan. specimens should be collected from a wide range of regions, Thus, it is possible that O. polyacantha is genetically differ- including the type locality of O. polyacantha, and taxonomic entiated even if it is similar in morphology, and the possibil- studies, including DNA analysis, should be carried out. ity that our examined specimens represent an undescribed The specimens described herein are clearly morphologi- species or subspecies cannot yet be precluded. In this study, cally different from the two species of Ophiopsila previously the specimens were tentatively identified as O. cf. polyacan- recorded in Japan, O. pantherina and O. squamifera. They New record of Ophiopsila cf. polyacantha from Japan 293 therefore represent a new record species of Ophiopsila for Japan. References The Japanese name is formed as a compound of “Kin- habu” (meaning “golden pit viper”). “Toranoo-kumohitode” Baker, A. N. 1974. New species of brittle-stars from New Zealand (Echi- (originated from Japanese genus name of Ophiopsila), re- nodermata: Ophiuroidea). Records of the Dominion Museum 8: ferring to vivid color patterns of O. cf. polyacantha, which 247–266. Brehm, P. and Morin, G. 1977. Localization and characterization of lu- reminds us of the yellow and white color pattern of the minescent cells in Ophiopsila californica and Amphipholis squama- Amami Islands variant of the Ryukyu Islands endemic pit ta (Echinodermata: Ophiuroidea). Biological Bulletin 152: 12–25. viper Protobothrops flavoviridis (Hallowell, 1861), locally Christodoulou, M., O’Hara, T. D., Hugall, A. F., and Arbizu, P. M. 2019. known as “Kin-habu”. Dark ophiuroid biodiversity in a prospective abyssal mine field. Ecological note. Our video observations reveal that this Current Biology 29: 3909–3912.e3. species flashes its arms when touched by metal forceps Clark, A. M. 1952. Some echinoderms from South Africa. Transactions (Supplementary Movie 1). We did not measure the spec- of the Royal Society of South Africa 33: 193–221. trum, but the bioluminescence color was green as in other Clark, A. M. and Rowe, F. W. E. 1971. Monograph of Shallow-Water In- species of Ophiopsila (O. aranea Forbes, 1843, O. californica do-West Pacific Echinoderms. British Museum (Natural History), London, ix+238 pp., 64 pls. A. H. Clark, 1921, O. pantherina, O. riseii Lütken, 1859 and Clark, H. L. 1915. Catalogue of recent ophiurans: based on the collec- O. xmasilluminans; see Brehm and Morin 1977; Shimo- tion of the Museum of Comparative Zoology. Memoirs of the Mu- mura 1986; Grober 1988; Vanderlinden and Mallefet 2004; seum of Comparative Zoölogy at Harvard College 25: 165–376. Woolsey et al. 2013; Okanishi et al. 2019). Sand burrow- Clark, H. L. 1918. Brittle-stars, new and old. Bulletin of the Museum of ing behavior of O. cf. polyacantha is similar to O. xmasillu- Comparative Zoölogy at Harvard College 62: 263–338. minans and different from another known sand burrowing Forbes, E. 1843. On the Radiata of the eastern Mediterranean. Transac- species, O. pantherina (Woolsey et al. 2013; Okanishi et al. tions of the Linnean Society of London 19: 143–153. 2019) in that the former two species extend only the distal Fujii, T. and Reimer, J. D. 2016. A new solitary free-living species of the portions of arms into the water (Fig. 2A). Considering that genus Sphenopus (Cnidaria, Anthozoa, Zoantharia, Sphenopidae) the known ecological features of ophiopsilid species include from Okinawa-jima Island, Japan. ZooKeys 606: 11–24. Gray, J. E. 1840. Room II. Pp. 57–65. In: British Museum (Ed.) Synopsis sand-burrowing and/or bioluminescence, these might be re- of the Contents of the British Museum. G. Woodfall and Son, Lon- garded as a general feature in this genus. Further in situ eco- don. logical observations of living animals are needed, to reveal Grober, M. S. 1988. Brittle-star bioluminescence functions as an apose- details of habitat and behavior. The accumulation of such matic signal to deter crustacean predators. Animal Behaviour 36: research will make a significant contribution to the under- 493–501. standing of further characterize species diversity of ophiu- Guille, A. and Jangoux, M. 1978. Astérides et Ophiurides littorales roids. de la région d’Amboine (Indonésie). 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