Comanthus kumi, Fujita & Obuchi, 2012

Fujita, Yoshihisa & Obuchi, Masami, 2012, Comanthus kumi, a new shallow-water comatulid (Echinodermata: Crinoidea: Comatulida: Comasteridae) from the Ryukyu Islands, Japan *, Zootaxa 3367 (1), pp. 252-268 : 262-267

publication ID	https://doi.org/ 10.11646/zootaxa.3367.1.24
persistent identifier	https://treatment.plazi.org/id/039B4449-E878-C55B-FF31-8CB6B32AFD17
treatment provided by	Felipe
scientific name	Comanthus kumi
status	sp. nov.

Treatment

Comanthus kumi n. sp.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype: Aka-todai , Kume Island , Ryukyu Islands (KUMEJIMA 2009, Diving St. 43), 26°19.251ʹN, 126°45.354ʹE, 11.6 m depth, 20 November 2009, night, SCUBA diving, coll. Y. Fujita, RUMF-ZE- 00025. GoogleMaps

Paratypes: Aka-todai, Kume Island, Ryukyu Islands , 26°19.251ʹN, 126°45.354ʹE, 8.6 m, 17 October 2010, night, SCUBA diving, coll. Y. Fujita, RUMF-ZE-00026. Same locality and data as RUMF-ZE-00026, 9.4 m, RUMF-ZE-00027. Maeda-misaki, Onna, Okinawa Island, Ryukyu Islands , 20.4 m, 28 May 2009, night, SCUBA diving, coll. Y. Fujita, RUMF-ZE-00028. Mizugama, Yomitan, Okinawa Island, Ryukyu Islands , 15.7 m, 4 January 2000, night, SCUBA diving, coll. Y. Fujita, RUMF-ZE-00029 GoogleMaps .

Comparative material. Comanthus gisleni Rowe, Hoggett, Birtles, & Vail, 1986 . Mizugama, Yomitan, Okinawa Island , Ryukyu Islands , 7.1 m, 1 December 1997, SCUBA diving, coll. Y. Fujita, RUMF-ZE-00030 ( Fig.5A View FIGURE 5 ).

Comanthus parvicirrus (Müller, 1841) . Maeda-misaki, Onna, Okinawa Island , Ryukyu Islands , 6.7 m, 12 August 2000, night, SCUBA diving, coll. Y. Fujita, RUMF-ZE-00031 ( Fig.5B View FIGURE 5 ) .

Diagnosis. A large species with elongated arms exceeding 300 mm in length. Centrodorsal small, 3.0–3.3 times radial length, discoidal. Radials visible, narrow. Disk small, smooth, hemispherical; mouth marginal; anal papilla central. Cirri weak, sometimes absent; mature cirri up to IV, 6–8 mm long, with 13–15 segments; aboral sides of distal segments each with transverse ridge. Arms 20–27 in number; anterior arms reaching 3 times longer than posterior arms. In IBr 2, IIBr, and IIIBr 4(3+4) or 2, each ossicle rounded laterally. First brachial syzygy at br 3+4, second at br 10+11~13+14, and following at 3–6 (usually 4) intervals of muscular articulations. Discretely combed pinnules present at intervals of varying length on the proximal 1/5 to 1/3 of each anterior, long arm (arising closest to mouth) and distal half of each posterior, short arm. P D and P 1 almost similar in shape and length, each with 7–14 comb teeth; P 2 shortest, with 7–14 teeth; proximal comb teeth saucer-shaped; primary comb teeth triangular, confluent, each accompanied by a small secondary tooth. Middle segments of distal pinnules with spinose distal aboral edges. Colouration in life almost uniform: white ground colour with yellow-orange broad blotches on the ossicles united by syzygy.

Description of holotype. Centrodorsal ( Figs. 1C, D View FIGURE 1 , 2A View FIGURE 2 ). Small, 2.9 mm in diameter, 3.2 times wider than radial length, low discoidal, pentagonal; marginal row of cirrus sockets producing rugged edge; polar area slightly concave, smooth.

Cirri ( Fig. 2F View FIGURE 2 ). Three mature (one broken through examination), 5 rudimentary, and 1 scar; 2 mature cirri each 6.8 and 7.7 mm long, composed of 14 or 15 segments. Cirrus segments each compressed laterally; first segment very short; second 1.5 times broader than long; third 1.3 times longer than broad; fourth to sixth segments 1.3–1.4 times longer than broad. Following segments squarish (approximately as long as broad) or gradually decreasing in length (mostly broader than long). Eighth to penultimate segments each with transverse ridge, bearing irregular minute spines on aboral margin. Terminal claw approximately twice as long as penultimate segment, curved, with sharply pointed apex.

Rays ( Figs. 1C, D View FIGURE 1 , 2A, B View FIGURE 2 ). Radials visible, 3.6 times broader than long, narrow, forming rounded pentagon. Division series, except for first ossicle, each well separated from adjacent ray branches. IBr series composed of 2 ossicles, connected tightly by synarthry; Ibr 1 short, 3.7–4.1 times broader than long, oblong, united laterally to neighboring ossicles; Ibr 2 2.1–2.2 times broader than long, axillary, triangular, laterally separated from neighboring ossicles. IIBr series all composed of 4 ossicles; IIbr 3 and IIbr 4 connected by syzygy; IIbr 1 short, 2.1–2.2 times broader than long, almost oblong, united interiorly; IIbr 2 short, 3.0–3.5 times broader than long, trapezoidal, laterally separated from neighboring ossicle, bearing P D; IIbr 4 pentagonal. Six IIIBr series (4 exterior and 2 interior) present; not twisted; all composed of 4 ossicles, IIIbr 3 and IIIbr 4 connected by syzygy.

Arms ( Figs. 1C, D View FIGURE 1 , 2B–E View FIGURE 2 ). Twenty-seven in number (2 arms broken and lost through examination); anterior and posterior rays 250–290 mm and 79–81 mm, respectively. Proximal brachials short, rounded laterally, broader than long; br 1 2.1–2.6 times broader than long, oblong, united interiorly to neighboring br 1; br 2 1.9–2.2 times broader than long, trapezoidal, with exterior margin much longer than interior margin, separated from neighboring ossicles; br 3 and br 4 1.4–1.9 times broader than long, articulated by syzygy; br 3+4 oblong; br 5 and br 6 nearly oblong, 1.6–2.0 and 1.5–1.8 times broader than long, respectively. Brachials succeeding middle ones 1.3–1.7 times broader than long, gradually diminishing in width distally, cuneate alternately. Brachials near arm tip 2.0–3.2 times longer than wide, slender, circular cylindrical. All brachials uniformly smooth. First arm syzygy at br 3+4; second at br 10+11 ~ 12+13; following intervals of 3 or 4 muscular articulations.

Pinnules ( Figs. 3 View FIGURE 3 , 4 View FIGURE 4 ). Unbroken arm (234 mm long) of anterior rays with at least 94 pinnules, short arm (74.3 mm long) of posterior rays with at least 33 pinnules. Genital pinnules on P 3 – P 15. Combed pinnules present discretely on P 20 – P 26 of anterior (long) arms (proximal 1/4 or 1/3 of arm) and on P 20 –P 27 of posterior (short) arms (at least half of arm). P D 10.5–13.1 mm long; proximal pinnulars broader than long, composed of 36–38 segments, with 7–10 comb teeth; middle to distal pinnulars with length and width subequal or longer than broad; proximal comb teeth saucer-shaped; primary teeth triangular, confluent with lateral margin of pinnular, with small secondary tooth. P 1 8.8–11.7 mm long, with 31–38 segments bearing 8–10 comb teeth; combed pinnulars as in P D. P 2 shortest, 4.0– 4.9 mm long, with 22–27 segments bearing 7–10 comb teeth. Following pinnules sometimes lacking combs: P 3 5.7 mm long, with 22–28 segments bearing 6–10 comb teeth; P 4 5.2 mm long, with 22 segments bearing 7 comb teeth. Pinnules on inner side of arm (P a, P b …) similar to in those on outer side of arm. Middle segments of terminal pinnules with fringe of spines on distal aboral edge ( Fig. 3D View FIGURE 3 ).

Disk. Small, ca. 13.6 mm in diameter, smooth, hemispherical; mouth marginal and anal papilla central.

Notes on Paratypes. Largest specimen (RUMF-ZE-00028). Centrodorsal 2.9 mm in diameter, 3.3 times wider than radial length; arms 26 in number, anterior arms 295–320 mm long, posterior arm 110–115 mm long; cirri X (4 mature, 4 rudimentary, and 2 sockets), mature cirri 7–8 mm long, composed of 15 or 16 segments; division series IBr 2, IIBr 4(3+4), IIIBr 4(3+4), IVBr 4(3+4); first arm syzygy at br 3+4, second at br 10+11 ~ 13+14; following intervals 3–6 (mainly 4) muscular articulations; proximal pinnules with 9–14 comb teeth, combed pinnules present on proximal 1/3 (at least P 30 of whole pinnules) in each anterior arm and extending nearly to tip of each posterior arm [P 36 of whole 46 pinnules].

Smallest specimen (RUMF-ZE-00029) ( Fig.1F View FIGURE 1 ). Centrodorsal 2.4 mm in diameter, 3.0 times wider than radial length; arms 20 in number, anterior rays 160 mm long, posterior 36–40 mm long; cirri VI (1 mature and 5 rudimentary), mature cirrus 6 mm long, composed of 13 segments; division series IBr 2, IIBr 4(3+4) or 2; proximal pinnules with 9–11 combs, combed pinnules present on proximal 1/5 to 1/4 [at least P 13 of whole 66 pinnules] of each anterior arm and on proximal 1/2 of each posterior arm (P 7 of whole 15 pinnules).

Colouration in life. Ground body white; centrodorsal stellate yellow-orange; aboral side of arms and brachial ossicles of rays and arms white; ossicles united by syzygy with yellow-orange broad blotches. Cirri yellow-orange. Pinnules white in aboral view, with yellow-orange blotches. Disk dark orange, with white blotches.

Etymology. The new species is named after the old name of Kume Island, Kumi, where the holotype of the species was collected. Used as noun in apposition. The standard Japanese name for this species is given here as “Nichirin-umishida”

Distribution. Known only from the Ryukyu Islands (Kume Island and Okinawa Island), Japan in 8.6–20.4 m.

Habitat. The whole body of the species is concealed in a crevice or small hole on the coral reefs during the day. However, several longer anterior arms of the species were protruded from the inhabited crevice at night. This suggests that Comanthus kumi n. sp. is a nocturnal species.

Remarks. Comanthus kumi n. sp. may be closest to C. gisleni in that the middle segments of the distal pinnules have a fringe of spines on each distal aboral edge ( Fig. 3D View FIGURE 3 ). However, the new species is distinguished from C. gisleni by the length of the anterior arm and the structure of the brachial ossicles. The anterior arm of C. kumi n. sp. is elongated and exceeds 300 mm in length, whereas that of C. gisleni is only at most 150–160 mm. The brachial ossicles are smooth and slightly rounded on the aboral and lateral surfaces in C. kumi , while they are flattened and everted laterally in C. gisleni (see Kogo, 1998; Rowe et al. 1986). The body colouration in life is also clearly different between the two species ( Figs. 1 View FIGURE 1 and 5 View FIGURE 5 ). In C. kumi n. sp., the colouration is almost uniform, the brachial ossicles are white in ground colour and the ossicles united by syzygy have yellow-orange broad blotches ( Fig. 1C, D, F View FIGURE 1 ); whereas in C. gisleni , the brachial ossicles vary in the ground colour (e.g. dark brown, black, brown, see Rowe et al. 1986; Fig.5 View FIGURE 5 ) and each possesses a darker longitudinal line on the dorsal midline.

Comanthus kumi n. sp. also resembles C. parvicirrus and C. suavia in having distinctly visible radials which are not obscured by the centrodorsal, and the relatively large centrodorsal of 2 times wider than the length of the radial. However, the new species differs from the latter two species in the presence of a fringe of spines on the distal aboral edge of the middle segments of each distal pinnule. Such a fringe of spines is absent in C. parvicirrus and C. suavia .