Discordipinna filamentosa, Chen & Suzuki & Shao, 2012

Chen, I-Shiung, Suzuki, Toshiyuki & Shao, Kwang-Tsao, 2012, A new deepwater goby of the genus Discordipinna Hoese & Fourmanoir, 1978 (Teleostei: Gobiidae) from Kumejima of the Ryukyus, Japan *, Zootaxa 3367, pp. 274-280 : 276-279

Discordipinna filamentosa n. sp.

(New Japanese name: Naginata-haze)

( Figs. 2–4)

Discordipinna sp. 1 . — Suzuki & Shibukawa 2004: 444.

Material examined. Holotype. NSMT-P104037 , 15.7 mm SL, Trawl 7, 80–82 m depth, GPS 26°23.090´N, 126°47.832´E, 1 m Beam Trawl , Kumejima, Okinawa Island, the Ryukyu Islands, Japan, coll. Liao Y.C. et al., 11 Nov. 2009.

Photographic records from Image Database of Fishes in the Kanagawa Prefectural Museum of Natural History , Japan ( KPM-NR). (A) Kumejima, the Ryukyu Islands, Japan: KPM-NR 36520, 64 m depth, H. Kobayashi, 26 Jun. 2000. (B) Okinawajima , the Ryukyu Islands, Japan: KPM-NR 38565, 37 m depth, U. Adachi, 3 Aug. 2000. (C) Tsutomezaki , Kashiwajima Island , Shikoku, Japan: KPM-NR 33814, 55 m depth, S. Kubo, 11 Oct. 1999. (D) Borneo Island , Malaysia: KPM-NR 22220, 30 m depth, F. Konno, 2 Jan. 1997 .

Diagnosis. Discordipinna filamentosa n. sp. can be well distinguished from the only other described species, D. griessingeri Hoese & Fourmanoir, 1978 , by the following unique combination of features: (1) fins: first dorsal fin rays VI; pectoral fin rays 16; and first dorsal fin with the longest, filamentous first ray in male extending far beyond caudal fin base when depressed; (2) squamation: longitudinal scale rows 26; transverse scale rows 8 and predorsal naked; (3) dorsal pterygiophore formulae 3/122101/9; 10 + 16 = 26 vertebrae; (4) head lateral-line system: a loosely arranged, longitudinal pattern of infraorbital papilla and anterior oculoscapular canal present (with median pore λ singular on middle of interorbital region, lateral section as pores α, β, and ρ) and preopercular canal (with three pores γ, δ and ε), lacking posterior oculoscapular canal; and (5) distinctive coloration: body generally creamy white; head with a snow-white oblique band from upper lip to upper part of opercle; dorsal side of snout scattered with tiny, densely-set tiny orange to brown spots; trunk with three lateral, oblique orange to brown bands which generally fused ventrally, and lateral body with 4–5 thin longitudinal yellow stripes; first dorsal fin yellow with 12 major transverse deep brown bands mainly on filamentous portion of the fin and an oval translucent mark on basal protion of that; second dorsal fin yellow with about four rounded gray blotches each having a central deep black spot against yellow background; caudal fin yellow with a shallow “C” shaped snowwhite mark basally and several round deep black spots on upper half; anal and pelvic fins entirely deep black; and pectoral fin with a snow-white wedge.

Description. Body proportions are described in Table 1. Body subcylindrical anteriorly, compressed posteriorly. Head modrate large, snout somewhat pointed in lateral view. Eye large, dorsolateral. Mouth somewhat oblique about 40 degrees to horizontal line, the rear margin extending slightly beyond vertical of anterior margin of eye. Lower lip anteriormost. Both jaws with 2–4 rows of tapered sharp teeth, and outer rows enlarged. Anterior nasal pore a short tube and posterior nasal pore a round opening. Gill-opening restricted, extending forward ventrally somewhat beyond a vertical at upper edge of the opening. Dorsal pterygiophore formula 3/122101/9. 10 + 16 = 26 vertebrae.

Fins. First dorsal fin rays VI; second dorsal fin rays I/8; anal fin rays I/8; pectoral fin rays 16. First dorsal fin elongate with the longest, filamentous first ray in male extending far beyond caudal fin base when adpressed. Origin of anal fin inserted just below origin of first branched ray of second dorsal fin. Rear tips of second dorsal and anal fins when adpressed do not reach procurrent rays of caudal fin. Pectoral fin rather large (32.1% in SL) and oblong, the rear margin extending beyond the vertical of origin of anal fin. Pelvic fin long (35.1% in SL) with large frenum and membrane arounf its spinous rays bilobed. Rear tip of pelvic fin extending beyond the vertical through anus. Caudal fin large (40.4%), elliptical with fin length longer than the head length.

Scales. Body with rather large ctenoid scales; belly scales cycloid; longitudinal scale rows 26; transverse scale rows 8; predorsal scale 0. Prepelvic and belly with cycloid scales. Head and predorsal region entirely naked.

Head lateral-line system. Canals: Anterior oculoscapular canal extension with anteriorly paired terminal pores σ slightly behind posterior nasal pore. Pore λ singular on middle of interorbital region; pore κ singular on rear dorsal vertical of orbit beyond pore λ. Paired pores ω behind eyes on nape. Lateral extension of anterior oculoscapular canal behind orbit as pore α, followed by middle pore β and terminal pore ρ. Preopercular canal present, with three pores: dorsally terminal pore γ; middle pore δ and ventrally terminal pore ε.

Papillae: Cheek with loosely arranged, longitudinal infraorbital papillae. Row a very short with four papillae, not extending to vertical through middle of eye. Row b short, merely with three papillae. Rows c and d longer with more papillae in row c, and row c extending posteriorly to vertical through poreα. Opercle with three main rows as rows os, ot and oi with both rows ot and oi slightly separated. Row f as paired papillae. Other papillae rows shown in detail as in Fig. 1.

Colouration in freshly preserved specimen. Body with generally creamy white background. Head creamy yellow to orange pinkish and an oblique, snow-white band from upper jaw to lower part of eye, then horizontally to posterior region of head to upper region of opercle. Dorsal side of snout and upper part of orbit scattered with tiny, densely-set orange to brown spots. Trunk with three rather oblique orange to brown bands which generally fuse ventrally, and lateral body with 4–5 very thin, longitudinal yellow stripes.

First dorsal fin light yellow with 12 major transverse deep brown bands mainly on filamentous portion of the fin and an oval translucent mark on basal protion of that. Second dorsal fin yellow with a translucent, longitudinal band on lower half region and also with four main gray marks each having a central deep black spot against yellow background. Caudal fin yellow with a shallow “C” shape snow-white mark, distal region with thin deep black margin surrounded by a thin snow white margin. Several round deep black spots on upper half of caudal fin membrane with the largest on upper region. Anal fin entirely deep black. Pelvic fin entirely deep black except anterior basal region in orange gray. Pectoral fin with a snow-white oblique, wide triangular wedge; upper 1/2 region of fin membrane with several tiny deep black spots.

Distribution. So far, the single specimen was collected from the deepwater trawling of up to 82 m depth off Kumejima, Ryukyu, Japan. However, some underwater photographic records taken by Japanese scuba divers have provided live images of this species around Kashiwajima, Shikoku, Japan; Okinawajima, the Ryukyu Islands, Japan; and Malaysia. Based on scuba diving witness and current trawl specimen record, it seems to live in 30 to 82 m depth water with substratum of coral-reef hard debris.

Etymology. The specific name referred to Latin-“ filamentum ” meaning the thread-like elongation of fin, a diagnostic feature, as very thin and long extension of the anterior two spinous rays of first dorsal fin.

Morphological comparison with the congeners. Discordipinna filamentosa n. sp. can be well distinguished from the type species, D. griessingeri Hoese & Fourmanior, 1978 , in this genus by the following features: (1) fin ray counts: first dorsal fin rays VI vs. V; pectoral fin rays 16 vs. 17–20; (2) dorsal pterygoiphore formula 3/122101/ 9 vs. 3/41001/8; (3) dorsal fin shape: first ray of first dorsal-fin longest in male vs. second ray of dorsal-fin base longest in male; and its fin membrane simply pointed vs. biforked; (4) head canals: preopercular canal present vs. preopercular canal absent; and (5) specific coloration pattern: head with a horizontal white band vs. many round, deep black spots; pelvic fin with a snow-white oblique, wide band vs. unmarked pale white background; first dorsal fin with about 12 transverse brown bands vs. entirely orange red; and anal fin entirely black vs. with lower 2/3 region orange red and upper 1/3 region translucent.

Although the difference of dorsal pterygoiphore formula between the two species can be observed, another shallow water species that resembles a Discordipinna ( Gobiidae , indet. Gen and sp. 14 sensu Suzuki & Shibukawa 2004) also shares the same dorsal pterygiophore formula (3/122101/9) with Discordipinna filamentosa . These three species share a similar longitudinal pattern of infraorbital papillae which can be considered as an essential feature for defining this gobioid genera (sensu Miller). The differentiation of the preopercular canal and dorsal pterygiophore formula may be considered as the potential features to separate them up to the generic level if there is further more morphological evidence likely from osteological sruvey. In addition, they share a reduced, longitudinal pattern of infraorbital sensory papillae and the feature of a restricted gill-opening, thus further anatomical and osteological evidences need to be gathered.