Nezumia shinoharai, Nakayama, Naohide & Endo, Hiromitsu, 2012

Nakayama, Naohide & Endo, Hiromitsu, 2012, A new grenadier of the genus Nezumia (Pisces: Gadiformes: Macrouridae) from southern Japan, Zootaxa 3410, pp. 61-68 : 62-67

Nezumia shinoharai sp. nov.

New English Name: Shinohara’s grenadier New Japanese Name: Shinohara-hige ( Figs. 1–4 ; Table 1 )

Holotype. NSMT-P 97667 (38.0 mm HL, 244+ mm TL), east of Boso Peninsula, 35º06.29’N, 140º50.2’E, 627–673 m depth, R/V Tansei-maru, cr. KT-95-15, sta. TB16, 3-m ORE beam trawl, 25 Apr. 1995.

Paratype. BSKU 44790 (33.3 mm HL, 198+ mm TL), Tosa Bay, 33º03.10’N, 133º36.91’E, 700 m depth, FRV Kotaka-maru, otter trawl, 24 May 1988.

Diagnosis. A species of Nezumia with the following combination of characters: pelvic fin rays 10; body scales covered with long, reclined, needlelike spinules in discrete parallel rows, posteriormost spinules extending well beyond scale margin; underside of head almost completely naked; cephalic sensory pores well developed especially on mandibular and infraorbital canals; teeth in broad cardiform bands in both jaws; snout long (31–34% HL), protruding well beyond upper jaw, ventral profile oblique; first dorsal fin uniformly dark with pale distal tip, second spinous ray not extremely elongated (height of first dorsal fin 99% HL); no prominent dark band encircling trunk.

Description. Data for the holotype are presented first, followed by those for the paratype, if different, in parentheses (see also Table 1 ). Pectoral fin rays i20–i21 (i23–i24); gill rakers on first arch (outer/inner) 9/11 (9/10); gill rakers on second arch 10/11 (10/10); lateral line scales over distance equal to predorsal length 38 (39); branchiostegal rays 7. The followings in percent of HL: snout length 31 (34); orbit diameter 30 (29); postrostral length 69 (68); upper jaw length 26 (27); internasal width 22; body depth at origin of first dorsal fin 80 (71); prepelvic length 102 (105); preanal length 134 (142); distance from isthmus to pelvic fin base 36 (35); distance from pelvic fin base to anal fin origin 37 (41); distance from anus to anal fin origin 24 (23); pelvic fin length 62 (65); pectoral fin length 55 (52); predorsal length 116 (113); length of first dorsal fin base 28 (23); interspace between first and second dorsal fins 41 (39).

General features shown in Figs. 1 and 2 . Body long, slender, gradually tapering from level of first dorsal fin to end of tail. Trunk short, laterally compressed, width over pectoral fin bases about 1.7 in depth below origin of first dorsal fin. Head rather short, about 6.5 in TL. Dorsal profile of head almost straight from tip of snout to nape. Snout long, protruding well beyond upper jaw, bluntly pointed in lateral and dorsal views. Ventral profile of snout oblique, forming an angle of about 45º to horizontal axis of head and body. Orbit large, circular, greatest diameter slightly shorter than snout length. Interorbital space gently depressed in preserved condition. Suborbital region moderately broad, divided into upper and lower parts by a longitudinal ridge. Mouth relatively small and inferior, about equal to or slightly shorter than interorbital width; upper jaw extending to below posterior 1/3 of orbit; posterior end of rictus slightly restricted by a lip fold. Lips relatively thick, papillaceous near teeth. Preopercle large, its hind margin inclined slightly backward and broadly rounded posteroventrally; preopercular ridge relatively low, forming a moderate backward extension at angle. Interopercle narrowly exposed beyond preopercle. Gill opening relatively narrow, extending forward to vertical under posterior margin of orbit; gill membranes broadly attached across isthmus with a posterior free fold. Outer and innermost gill slits restricted by folds of skin attached to upper and lower ends of gill arch. Gill rakers developed into short, spinous tubercles; those of outer series on first arch somewhat smaller. Barbel moderately long, terminating into a fine distal tip.

Anus and urogenital opening surrounded by a narrow periproct (black naked skin) that is situated closer to inner bases of pelvic fin than to origin of anal fin. Anterior dermal window of light organ small, narrow, extending from periproct to just behind a line connecting outer bases of pelvic fin.

*Transverse scale rows from midbase of first dorsal fin to lateral line

**Transverse scale rows from origin of second dorsal fin to lateral line

Teeth long, slender, conical, in broad tapered bands in both jaws; premaxillary band widest near symphysis with about seven teeth rows, extending almost 3/4 length of rictus; outer series distinctly enlarged. Dentary band similar to those of premaxillary, but no teeth significantly enlarged. All teeth deeply embedded in thick layer of gum papillae.

Body fully scaled except for periproct and anterior dermal window. Scales on body small, thin, relatively deciduous, covered with long, reclined, needlelike spinules in discrete parallel rows; those on dorsum below interdorsal space with 7 or 8 spinule rows; height of spinule on each row gradually increasing posteriorly, the last spinule extending well beyond scale margin; reticulate structure moderately developed on posterior part of unexposed field. Scales behind first dorsal, pectoral, and pelvic fins, and beneath gill covers lacking spinules. Grooved lateral line well developed, not interrupted throughout. Fins completely naked except proximal part of pelvic fin densely covered with minute scales.

Head mostly scaled except for lips, chin barbel, gular and branchiostegal membranes, and a narrow region around anterior nostril. Paired T-shaped areas on dorsal surface of snout narrowly naked. Underside of head naked from tip of snout to below posterior margin of suborbital shelf, the naked area extending onto lower margin of preopercle and entire mandibular ramus. Scales on head generally similar to those on body, except that spinules more erect and arrayed in somewhat divergent rows. Snout tipped with two large, closely adjoined tubercles; lateral angles armed with stout scutelike scales. Suborbital shelf formed of three rows of coarsely modified scales.

Cephalic sensory canals developed, but not broaden or swollen. Counts of open pores as follows ( Fig. 3 ): mandibular pores 7; preopercular pores 6; infraorbital pores 9; supraorbital pores 2; occipital pores 1; temporal pores 5; supratemporal pores 2. Pores on underside of head prominently enlarged; those on dorsal and lateral surfaces relatively small. Superficial neuromasts serially arranged along supraorbital, infraorbital, and mandibular canals, but densely scattered on underside of snout. Neuromasts below leading edges of snout modified to large knoblike papillae. Anterior nostril small and circular; posterior nostril large and bean-shaped; septum separating both nostrils forming an anteriorly-opened hood. Olfactory bulb oval, formed of 24–28 lamellae.

First dorsal fin short based, originating slightly behind vertical through pectoral fin insertion; first spinous ray splintlike, closely adhered to second spinous ray; second spinous ray fairly long, about equal to HL, armed along leading edge with small, sharp, reclined denticles. Interspace between first and second dorsal fins moderately wide, nearly equal to postorbital length. Second dorsal fin poorly developed, originating above base of eighth or ninth anal fin ray. Pectoral fin moderately short; upper base on a longitudinal line passing through midorbit. Pelvic fin inserted just below pectoral fin base; outermost ray slightly prolonged, extending backward to base of eighth to tenth anal fin ray. Anal fin well developed, much higher than second dorsal fin.

Coloration. In 75% ethanol, ground color tawny to swarthy. Chest black. Abdomen dusky violet. Underside of head generally black, except for pale chin. Orbit marked with a narrow dark rim. Lips mostly pallid, but sharply delineated in black. Barbel pale, but darker at base. Oral cavity uniformly black, except for pale gum papillae. Gill chamber mostly black, but paler on ceratohyal, epihyal, and anterior to lower end of cleithrum; gill rakers and arches dark; gill filaments pale. First dorsal fin uniformly dark with pale tip; second dorsal fin immaculate overall; pectoral fin dusky with a small black spot near lower base; pelvic fin uniformly black; anal fin dark anteriorly, but paler posteriorly. Color when fresh (based on photograph of the paratype; Fig. 2 ) almost same as that in preserved specimens, but much darker overall.

Distribution. Nezumia shinoharai is currently known only from off Boso Peninsula and Tosa Bay, southern Japan, at depths of 627– 700 m.

Etymology. The new species is named in honor of Dr. Gento Shinohara of the National Museum of Nature and Science, Tokyo, for his great contributions to our knowledge of the deep-sea fish fauna around Japan.

Remarks. Since both the holotype and paratype of N. shinoharai were collected by bottom trawls, some of their characters are partially damaged. The holotype is in excellent condition but with a damaged abdomen where the intestine is exposed to the outside ( Fig. 1 ). In the paratype, the tip of first dorsal fin is broken and no body scales remain except on the isthmus and predorsal region. Compared to the larger holotype, the paratype has a higher count of pectoral fin rays (i23–i24 vs. i20–i21) and fewer and rather widely spaced serrations along leading edge of first dorsal fin. We conclude that these differences are attributed to individual and size-related variations, respectively, and the gaps will be filled when more specimens become available.

Among more than 40 species of the genus, N. shinoharai is most similar to the following four species: N. aspidentata Iwamoto and Merrett, 1997 currently know only from the holotype from New Caledonia; N. holocentra ( Gilbert and Cramer, 1897) distributed in the Hawaiian Archipelago; N. merretti Iwamoto and Williams, 1999 known from three specimens including the two types from the Western Australia and an additional specimen recently collected from the eastern Indian Ocean off Indonesia (HUMZ 190198); N. spinosa (Gilbert and Hubbs, 1916) widely distributed from Japan (type locality) to Australia as well as southern Africa. The five species share the following features: snout long, protruding well beyond upper jaw; pelvic fin rays 8–10; underside of head almost entirely naked with prominent open pores; teeth in both jaws in broad cardiform bands; no dark band encircling trunk.

Nezumia shinoharai is distinguished from all of these species by its unique spinulation on body scales, viz., spinules are long, extending well beyond the scale margin, and arranged in discrete parallel rows ( Fig 4 ). In N. aspidentata and N. holocentra , spinules are arrayed in convergent rows. In N. merretti , they are much shorter, not overlapping the scale margin as extensively, and arranged in more tightly parallel rows. In their original description of N. spinosa, Gilbert and Hubbs (1916) provided an excellent illustration of the holotype where body scale spinules are arranged in parallel to convergent rows (pl. 10, fig. 2), although they noted that “scales with long retrorse spinules, arranged in quincunx order”. This illustration was subsequently used by Iwamoto and Merrett (1997) and Iwamoto and Williams (1999). Based on our examination of the holotype of N. spinosa , body scales are covered with numerous spinules densely scattered over the exposed field ( Fig. 4 E). The new species further differs from N. holocentara , N. merretii , and N. spinosa in having 10 pelvic fin rays (vs. 8 or 9), and from N. aspidentata in having more prominent sensory pores especially on the infraorbital and mandibular canals. Several measurements given in Table 1 are also useful for separating the new species from the other four.

Iwamoto and Williams (1999) noted notable differences in frequency distributions of several counts and measurements between Australian and African populations of N. spinosa , suggesting these populations may represent different species with disjunct distributions. In addition to the differences of body scale structure and pelvic fin ray count mentioned above, the new species is further distinguished from our materials of N. spinosa including the holotype, one from the South China Sea, and six from Australia, in having a lower first dorsal fin (99% HL vs. 120–138%), a longer preoral length (29–30% vs. 18–26%), and a shorter postorbital length (39–42% vs. 44–47%).

Nezumia shinoharai is extremely rare in Japanese waters, considering how thoroughly the region has been explored over the past century. Although Tomio Iwamoto of the California Academy of Sciences and the present authors have checked extensive collections deposited in BSKU, NSMT, HUMZ, FAKU, and ZMUT, no additional specimens of this species were found.

Comparative material examined. Nezumia aspidentata : MNHN 1996-0958 (holotype, 34.2 mm HL, 193 mm TL), off New Caledonia, 19º39.0’S, 158º49.0’E, 700–720 m depth, 18 Oct. 1986. N. holocentra : USNM 47723 (questionable paratype, 39.6 mm HL, 171+ mm TL), off Hawaii, 21º12’00”N, 157º38’30”W, 686 m depth, 6 Dec. 1981; BPBM 24579 (5 specimens, 35.7–38.6 mm HL, 151+–181+ mm TL), off Hawaii, 650 m depth, 10 Mar. 1971. N. merretti : CSIRO H 2584--20 (holotype, 54.3 mm HL, 244+ mm TL), off Western Australia, 18º04’S, 112º42’E, 853–854 m depth, 1 Feb. 1991; CSIRO H 1966--01 (paratype, 39.3 mm HL, 203+ mm TL), off Queensland, 18º59’S, 150º32’E, 879–886 m depth, 25 Nov. 1985; HUMZ 190198 (1, 36.7 mm HL, 183+ mm TL), northwest of Sumatra Island, 5º29.16’N, 93º44.14’E, 568–590 m, 13 Oct. 2004. N. spinosa : USNM 76868 (holotype, 46.4 mm HL, 262+ mm TL), East China Sea, 31º31’N, 129º25’30”E, 781 m depth, 12 Aug. 1906; BSKU 16687 (1, 35.5 mm HL, 183+ mm TL) and BSKU 16688 (1, 19.4 mm HL, 130 mm TL), Timor Sea, 9º27.0’S, 127º58.6’E, 690–850 m depth, 18–19 Jun. 1972; CSIRO H 1961--01 (1, 40.4 mm HL, 197+ mm TL), off Queensland, 18º54’S, 150º29’E, 1005–1013 m depth, 25 Nov. 1985; CSIRO H 1971--01 (1, 40.8 mm HL, 199+ mm TL), off Queensland, 16º55’S, 151º34’E, 880 m depth, 6 Dec. 1985; CSIRO 2549--10 (1, 48.8 mm HL, 254+ mm TL), off Western Australia, 21º51’S, 113º46’E, 650–685 m depth, 24 Jan. 1991; CSIRO 2580--04 (1, 47.5 mm HL; 249+ mm TL), off Western Australia, 27º06’S, 112º22’E, 713–714 m depth, 31 Jan. 1991; SFC 1840 (1, 37.0 mm HL, 176+ mm TL), South China Sea, 604–680 m depth, Apr. 1982.

Figures

FIGURE 1. Holotype of Nezumia shinoharai sp. nov. NSMT-P 97667, 38.0 mm HL, 244 + mm TL. Lateral view of preserved specimen. Scale bar = 20 mm.

FIGURE 2. Paratype of Nezumia shinoharai sp. nov. BSKU 44790, 33.3 mm HL, 198 + mm TL. (A) lateral view of fresh specimen; (B) dorsal and (C) ventral views of preserved specimen. Scale bar = 20 mm.

FIGURE 3. Illustrations showing cephalic sensory pores and head squamation of Nezumia shinoharai sp. nov., holotype, NSMT-P 97667, 38.0 mm HL, 244 + mm TL. (A) lateral view; (B) dorsal view; and (C) ventral view.

FIGURE 4. Body scales of five species of Nezumia. (A) N. shinoharai sp. nov., holotype, 38.0 mm HL; (B) N. aspidentata, MNHN 1996 - 0958, holotype, 34.2 mm HL; (C) N. holocentra, BPBM 27579, 38.6 mm HL; (D) N. merretti, CSIRO H 1966 -- 0 1, paratype, 39.3 mm HL; (E) N. spinosa, USNM 76868, holotype, 46.4 mm HL; and (F) N. spinosa, CSIRO H 2594 -- 10, 48.8 mm HL. All scales are from region below interspace between first and second dorsal fins.

Tables

TABLE 1. Selected counts and measurements of five species of Nezumia.

	N. shinoharai	N. merretti	N. aspidentata	N. holocentra	N. spinosa
	n =2	n =3	n =1	n =15	n =8
TL (mm)	244+ (198+)	203+–244+	193	151+–181+	130–262+
HL (mm)	38.0 (33.3)	36.7–54.3	34.2	30.9–39.6	19.4–48.8
% of HL
Postorbital length	42 (39)	38–46	39	43–45	28–32
Distance from orbit to preopercle	35 (34)	32–33	30	35–37	35–40
Suborbital width	15 (14)	12–13	13	11–13	11–16
Preoral length	29 (30)	23–31	27	19–22	18–22
Interorbital width	25 (23)	19–21	21	18–20	19–21
Height of 1st dorsal fin	99	115	102	98–119	120–123
Length of outer gill slit	14 (12)	12–14	10	11–13	10–14
Length of barbel	12 (11)	6–12	6	7–11	9–14
Counts
1st dorsal fin rays	II,9	II,10–11	II,8	II, 9–11	II,8–10
Pelvic fin rays	10	8–9	10	9	8
Scales below 1D midbase*	7.5	5.5	8.5	6.5–7.5	5.5–9
Scales below 2D origin**	9 (8)	6.5–8	9	8.5–9.5	7.5–8.5