Breviturma securis sp. nov.

urn:lsid:zoobank.org:act: C8B521E9-09DA-4D3B-98C6-8AB7C388E0FD

Figs 2–4

Ophiocoma brevipes – Chao et al. 1991: 118–119 (in part), fig. 1c–d. — Hung 2000: 167 (in part), fig. 522. [non O. brevipes Peters, 1851].

Breviturma sp. – Ryanskiy 2020: 33, unnumbered fig.

Ophionereis sp. – Ryanskiy 2020: 36, unnumbered fig.

Ophiodermatidae sp. – Ryanskiy 2020: 48, unnumbered fig.

Breviturma aff. dentata – Shih et al. 2023: 125 (in list).

Diagnosis

The dorsal disc is densely covered with fine granules (Fig. 2C) that extend seamlessly to the ventral side. The oral shields are subequal in length and width (Figs 2D, 3C), while the adoral shields are spear-shaped (Figs 2D, 3D). There are four oral papillae and 10–12 tooth papillae (Fig. 2D). The dorsal arm plates are transversely elliptical (Figs 2E, 3G). The number of arm spines ranges from three to four, with the second dorsalmost arm spines on the 15 th –18 th arm segments being the longest and exhibiting slightly swollen tips (Fig. 2E–F). The ventral arm plates are pentagonal (Figs 2F, 3H), each bearing two oval tentacle scales on its lateral sides (Fig. 2D, F). The coloration of the dorsal disc is variegated, ranging from yellowish-gray to greenish-gray (Figs 2A, 4), with a dark, axe-shaped central pattern on the dorsal arm plates (Figs 2E, 4). The arms are transversely banded (Figs 2A, 4), with the arm spines showing a light gray base color and irregular, darker annulation (Fig. 2E–F). The ventral side is uniformly light in color (Fig. 2B).

Etymology

The species name securis is derived from the Latin word meaning ‘axe’, referencing the axe-shaped dark patterns on the dorsal arm plates. The name is used as a noun in apposition.

Type material

Holotype TAIWAN – Taitung County • (DD = 14.99 mm); Lanyu, Hongtou; 22°01′19.4″ N, 121°33′29.7″ E; depth <1 m; 28 Sep. 2022; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17232.

Paratypes TAIWAN – Taitung County • 1 spec. (DD = 12.00 mm); same data as for holotype; NCHUZOOL 17233 • 3 specs (DD = 8.72–15.74 mm); Lanyu, Hongtou; 22°01′19.4″ N, 121°33′29.7″ E; depth <1 m; 11 Mar. 2023; K. Chang et al. leg.; NCHUZOOL 17234 • 1 spec. (DD = 9.40 mm); Lanyu, Hongtou; 22°01′19.4″ N, 121°33′29.7″ E; depth <1 m; 22 May 2023; K. Chang et al. leg.; NCHUZOOL 17235 • 1 spec. (DD = 4.43 mm); Lanyu, Langdao; 22°04′52.9″ N, 121°32′07.9″ E; depth 7 m; 4 Jul. 2023; K. Chang et al. leg.; NCHUZOOL 17236 • 4 specs (1 spec. disc and 1 arm dissected, 4 arms in ethanol) (DD = 10.24–14.70 mm); Lanyu, Dongcing; 22°03′23.1″ N, 121°33′56.8″ E; depth <1 m; 13 Sep. 2023; K. Chang et al. leg.; NCHUZOOL 17237 • 1 spec. (disc broken); Lanyu, Langdao; 22°04′45.3″ N, 121°31′47.9″ E; depth <1 m; 15 Sep. 2023; K. Chang et al. leg.; NCHUZOOL 17238.

Other material examined

TAIWAN – Penghu County • 2 specs (DD = 11.77–12.31 mm); Wang’an, Dongjiyu; 23°15′24.9″ N, 119°39′59.4″ E; depth <1 m; 22 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17248 • 2 specs (DD = 12.85–13.91 mm); Wang’an, Dongjiyu; 23°15′20.5″ N, 119°40′03.1″ E; depth <1 m; 22 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17249 • 2 specs (DD = 7.67–16.00 mm); Wang’an, Dongjiyu; 23°15′12.0″ N, 119°40′02.9″ E; depth <1 m; 23 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17250 • 1 spec. (DD = 7.69 mm); Wang’an, Dongjiyu; 23°15′02.9″ N, 119°39′54.0″ E; depth <1 m; 23 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17251 • 8 specs (DD = 8.07– 11.39 mm); Wang’an, Dongjiyu; 23°15′24.9″ N, 119°39′59.4″ E; depth <1 m; 24 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17252 • 1 spec. (DD = 9.56 mm); Wang’an, Dongjiyu; 23°15′20.5″ N, 119°40′03.1″ E; depth <1 m; 25 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17253 • 1 spec. (DD = 14.47 mm); Wang’an, Dongyupingyu; 23°15′19.1″ N, 119°30′40.0″ E; depth <1 m; 26 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17254 • 3 specs (DD = 9.92–13.75 mm); Wang’an, Dongyupingyu; 23°15′21.0″ N, 119°30′45.9″ E; depth <1 m; 26 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17255 • 5 specs (DD = 12.38–17.65 mm); Wang’an, Dongyupingyu; 23°15′19.1″ N, 119°30′40.0″ E; depth <1 m; 27 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17256 • 4 specs (DD = 8.58–12.23 mm); Wang’an, Dongyupingyu; 23°15′29.1″ N, 119°30′46.5″ E; depth 1 m; 28 Apr. 2024; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17257. – Pingtung County • 1 spec. (DD = 10.87 mm); Siaoliouciou, Duzaiping; depth <1 m; 5 Sep. 2007; K.-S. Lee leg.; NMNS 005621-00012 • 2 specs (DD = 9.39–14.15 mm); Siaoliouciou, Shanfu Fishery Harbor; 22°20′24.4″ N, 120°21′46.2″ E; depth <1 m; 12 Feb. 2023; K. Chang and Y.-C. Hsu leg.; NCHUZOOL 17239 • 6 specs (DD = 8.64–14.61 mm); Checheng, Huangjin Beach; 22°04′52.6″ N, 120°42′06.2″ E; depth <1 m; 25 Feb. 2024; K. Chang et al. leg.; NCHUZOOL 17242 • 2 specs (DD = 13.53–15.23 mm); Hengchun, Nanwan; depth 1 m; 10 Jan. 1991; S.-M. Chao leg.; NMNS 002270-00012 • 1 spec. (DD = 13.38 mm); Hengchun, Tiaoshih, Kenting Great Tide Pool; 26 Jul. 2005; S.-M. Chao and S.-T. Huang leg.; NMNS 004875-00025 • 15 specs (DD = 4.75–15.50 mm); Hengchun, Houbihu; 21°56′18.9″ N, 120°44′43.6″ E; depth <1 m; 25 Dec. 2023; K. Chang et al. leg.; NCHUZOOL 17240 • 7 specs (DD = 3.61–10.98 mm); Hengchun, Wanlitong; 21°59′45.6″ N, 120°42′16.5″ E; depth <1 m; 26 Dec. 2023; K. Chang et al. leg.; NCHUZOOL 17241 • 1 spec. (DD = 9.60 mm); Hengchun, Dingtanzih; 21°55′56.8″ N, 120°44′42.2″ E; depth <1 m; 26 Feb. 2024; K. Chang et al. leg.; NCHUZOOL 17243 • 1 spec. (DD = 8.76 mm); Hengchun, Dingtanzih; 21°55′54.2″ N, 120°44′42.9″ E; depth 8 m; 26 Feb. 2024; K. Chang et al. leg.; NCHUZOOL 17244 • 1 spec. (DD = 6.58 mm); Hengchun, Wanlitong; 21°59′44.4″ N, 120°42′22.2″ E; depth <1 m; 26 Feb. 2024; K. Chang et al. leg.; NCHUZOOL 17245 • 5 specs (DD = 3.96–13.93 mm); Hengchun, Wanlitong; 21°59′42.4″ N, 120°42′22.3″ E; depth 5 m; 28 Feb. 2024; K. Chang et al. leg.; NCHUZOOL 17247 • 1 spec. (DD = 13.75 mm); Mudan, Gangzaibi; 22°08′49.8″ N, 120°53′32.4″ E; depth <1 m; 27 Feb. 2024; K. Chang et al. leg.; NCHUZOOL 17246. – Taitung County • 1 spec. (DD = 11.37 mm); Chenggong, Duli; 23°01′14.7″ N, 121°20′08.0″ E; depth <1 m; 15 Oct. 2024; K. Chang et al. leg.; NCHUZOOL 17338 • 5 specs (DD = 6.42–10.79 mm); Donghe, Dulan; 22°51′51.7″ N, 121°12′34.9″ E; depth <1 m; 16 Oct. 2024; K. Chang et al. leg.; NCHUZOOL 17339.

Description

Holotype

DD 14.99 mm (Fig. 2A–B). Dorsal disc and radial shields densely covered with spherical granules (279 per mm², Figs 2A, C, 5A), extending ventrally to distal end of oral shields (Fig. 2D). Oral shields subequal in length and width, L /Wca 1.1 (Figs 2 D, 5B), broadest mid-part, lateral edges slightly convex, converging distally. Madreporite enlarged, rounded. Adoral shields spear-shaped; adradial edge covered by oral shield, proximal abradial edge slightly concave (Fig. 2D). Four rectangular oral papillae per jaw half, distal-most widest. Lyman’s ossicles slender, posterior to distal-most oral papillae. 10–12 rounded tooth papillae on jaw tip (Fig. 2D). Genital slits extend from oral shields to disc margin. Five arms. Dorsal arm plates transversely elliptical, W/ L ca 2.2 (Figs 2E, 5C), slightly convergent proximally, straight distally, rounded laterally. Arm spines freestanding, cylindrical, tapering terminally (Fig. 2E–F). Second dorsalmost arm spines on 15 th –18 th arm segments longest, slightly swollen at tip. Arm spines sequence of proximal 20 segments: 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4(3), 4(3), 3, 3, 3, 3. First ventral arm plates rounded-triangular, W>L (Fig. 2D); following plates pentagonal, subequal in width, length, convex distally, proximally lateral edges concave for tentacle scales (Fig. 2F). Two equal oval tentacle scales, slightly longer than wide, arranged in a narrow angle (Fig. 2F).

Ossicles

One paratype, NCHUZOOL 17237. DD = 14.70 mm. Radial shields triangular, with all tips rounded (Fig. 3A). Adradial genital plate bar-like, slightly longer than abradial genital plate, proximal three quarters flattened, thin, distal end thicker, with an articulation for abradial genital plate (Fig. 3B 1). Abradial genital plate slightly bended, flattened thoroughly except for distal end (Fig. 3B 2). Oral genital plate thin, C-shaped (Fig. 3B3). Oral shields pear-shaped, L/W = 1.4, widest near middle part (Fig. 3C 1). Madreporite enlarged, round, distal hole large, one oval hydropore at distal lateral edge (Fig. 3C 2). Adoral shields spear-shaped, sharp at distal end, adradial and abradial sides slightly concave (Fig. 3D). Dental plate outer part with five tooth sockets, dorsalmost two penetrated (Fig. 3E 1), outer ventral part with nine small tooth papillae sockets, inner ventral half with five horizontal ridges (Fig. 3E 2). Oral plates abradial side with well-defined horizontal muscle flanges (Fig. 3F 1), adradial side with strong folds (Fig. 3F 2). Dorsal arm plates transversely elliptical, W/ L = 1.67, slightly convex distally, proximal lateral edges convergent (Fig. 3G). Ventral arm plates pentagonal, subequal in length and width, distal edge strongly convex, proximal edge with an angle of about 90°, lateral edges with notches on each side for tentacles and tentacle scales (Fig. 3H). Lateral arm plates strongly arched, outer side with four arm spine articulations (Fig. 3I 1), inner ventral part with a perforation (Fig. 3I 2). Vertebrae subequal in height and width, articulation zygospondylous, dorsal and ventral grooves present, dorsal lateral edge smooth and rounded, ventral lateral edge convergent (Fig. 3J).

Paratypes and non-type variations

Paratypes DD 4.43–15.74 mm, non-types DD 3.61–17.65 mm. Disc granules denser in smaller individuals, reaching 408/ mm² (Fig. 5A). Oral shields ratios stable across all sizes (Fig. 5B). W/L ratios of dorsal arm plates lower in young individuals, higher in larger specimens (Fig. 5C). Four arm spines from proximal arm segments in almost all examined specimens, five arm spines in only two specimens. Second dorsalmost arm spines from 15 th –18 th arm segment of most large individuals prominently elongated, swollen, absent in smaller individuals (Fig. 5D). For the detailed results, see Morphological analyses on Breviturma securis sp. nov.

Coloration

In life, the dorsal disc and ventral interradial areas exhibit a yellowish-gray to greenish-gray coloration, variegated with lighter and darker patches. These regions are adorned with discontinuous short dark lines that never form a reticular pattern (Figs 2A, 4A–D). In juveniles, a dark ‘star’ may occasionally appear at the center of the disc but never connects to the arm base (Fig. 4E–F). Dorsal arm plates share the disc’s background color but feature a dark ‘axe-shaped’ pattern in the center, the ‘axe bit’ is at proximal side and the ‘axe poll’ is at the distal side (Fig. 2E). Darker plates occur every two to three segments on both the dorsal and ventral arm plates, giving the arms a transversely banded appearance (Figs 2A, 4A–F). Arm spines are light gray with irregular darker annulations (Fig. 2E–F). Oral shields, jaws, and ventral arm plates are very light in color, either white or creamy yellow (Fig. 2B, D, F). Tentacle scales are white, occasionally exhibiting tiny dark dots (Fig. 2D, F). Tube feet are white (Fig. 2D, F).

Ecological and behavioral notes

This species inhabits sandy substrates beneath rocks, ranging from the intertidal zone to shallow subtidal depths of up to 8 m. It is highly sympatric with other brittle stars, including B. dentata, B. krohi, Ophiocoma scolopendrina, and Amphipholis squamata (Delle Chiaje, 1828). On one occasion, an individual was parasitized by a snail (Eulimidae sp.) attached at the base of an arm (Fig. 4G–H).

Distribution

Reunion Island; Taiwan; Papua New Guinea.

Remarks

Breviturma securis sp. nov. was previously misidentified as B. brevipes in Taiwan, including in academic literature (e.g., Chao et al. 1991) and in field guides (Hung 2000). The photographs for B. brevipes in those publications obviously match the new species in both morphology and coloration, showing strong arm spines, a greenish base color, variegated dark and light spots, and a conspicuous dark ‘axe’ pattern on the dorsal arm plates. For the same reasons, in a field guide to tropical Indo-Pacific echinoderms (Ryanskiy 2020), three records were identified as Breviturma sp., Ophionereis sp., and Ophiodermatidae sp., respectively; all should be referred to this new species. In our previous work (Shih et al. 2023), the new species was recorded from Lanyu, Taiwan, under the name Breviturma aff. dentata because of the presence of four strong arm spines, yet it exhibited a completely different coloration from the typical B. dentata (Müller & Troschel, 1842). The specimens from Lanyu are now designated as the holotype and paratypes in this study.

Furthermore, three specimens labeled as “ Ophiocoma brevipes ” archived in the NMNS (see Other material examined under Breviturma securis sp. nov.) were reexamined and confirmed to belong to this new species. These two species can be distinguished by their coloration and the number of AS on the proximal arm segments (see Discussion).