Coelorinchus fuscigulus, Iwamoto, Tomio, Ho, Hsuan-Ching & Shao, Kwang-Tsao, 2009

Iwamoto, Tomio, Ho, Hsuan-Ching & Shao, Kwang-Tsao, 2009, Description of a new Coelorinchus (Macrouridae, Gadiformes, Teleostei) from Ta i w a n, with notable new records of grenadiers from the South China Sea, Zootaxa 2326, pp. 39-50 : 40-45

Coelorinchus fuscigulus sp. nov.

Figs 1 A–E, 2A–B; Table 1

Coelorinchus cylindricus (non Iwamoto and Merrett, 1997): Shao et al. 2008: table 2 (listed, one spec.; northeastern Taiwan; 400–600 m).

Holotype. ASIZP 70169 (female, 74.8 mm HL, 322 mm TL); 24.94°N, 121.9°E, Tashi, Yilan, northeastern Taiwan; coll. H-C Ho; 23 May 2007.

Paratypes. Northeastern Taiwan: ASIZP 63249 (56.1 HL, 233 TL), Tashi, Yilan, coll. H-C Ho, 21 Mar 2004. ASIZP 66922 (66.2 HL, 286 TL), R/V Ocean Researcher I, st. CP248, 24.8656°N, 122.0411°E, 536 m, 28 Aug 2004. ASIZP 66973 (72.7 HL, 293 TL), Nanfangao fish market, coll. H-C Ho, 26 Jan 2007. ASIZP 70168 (77.1 HL, 301+ TL) and CAS 228337 (ex. ASIZP 70168)(2, 66.9–74.1 HL, 302+-285+ TL), Tashi, Yilan, coll. H-C Ho, 29 Jun 2007. CAS 228338 (ex CAS 224583, in part) (66.9 HL, 266 TL), Nanfangao fish market, coll. H-C Ho (field no. NFOFM 30-VIII-2005). East China Sea: ASIZP 63193 (52.2 HL, 228 TL) and CAS 224492 (ex. ASIZP 63193) (45.4 HL, 190 TL), 25°75’N, 123°48’E, Diaoyutai Archipelago, Yilan, Taiwan, coll. H-C. Ho, 24 Apr 2004.

Diagnosis. A species of Coelorinchus with two dermal windows of light organ, one immediately before anus, the other in a shallow fossa on chest just behind isthmus, the two windows not connected by an externally visible black mesial line; snout moderately elongated, 1.4–1.7 times orbit diameter, tipped with a sharp terminal scute, anterolateral margins incompletely supported by bone; underside of head fully naked except for scales along anterolateral snout margin and occasional isolated cluster below junction of preopercle and infraorbital ridges (above angle of lower jaw); rays of second dorsal fin high, about equal to opposite members of anal fin; spinules on body scales small, in 10–14 parallel rows; about 8–11 saddle bands on body; branchiostegal membranes prominently black or blackish, chest and abdomen blue; gums and upper oral valve dark.

Counts and Measurements. See Table 1 .

Description of holotype. (data for paratypes in parentheses). ─Body and head long, slender, relatively shallow; head about 4.3 (3.9–4.5) in TL, body width about 1.26 (1.2–1.4) into greatest body depth; trunk long, length isthmus to anal fin 104% (82–104%) of HL. Snout sharply pointed, terminal scute horizontally flattened with tiny spines more or less longitudinally arrayed; the scute flanked at base and adjoined at each side by much smaller scute-like scale. Suborbital ridge sharply separates dorsal and ventral parts of head; ridge composed of a row of modified, thickened scales, dorsal to which a second row of somewhat smaller but thickened scales run from below nasal fossa to posterior end of ridge. Scales above ridge rows more normal shaped, with finer, sharper spinules. Nasal fossa naked except ventral and anteroventral margins, which have small scales (paratypes vary from almost no scales on fossa to condition in holotype). Bridge between nasal fossa and orbit narrow but fully scaled. Underside of head almost entirely naked except for margin of scales along anterolateral edges of snout and cluster of small scales seemingly encroaching from junction of infraorbital and preopercular portions of suborbital ridge onto naked surface above angle of lower jaw (few or no scales above angle of lower jaw in paratypes). Subopercle extended ventrally into a short tab protruding beyond preopercle margin.

Mouth subinferior, upper jaw less than one-third of head length, upper jaw extends posteriorly to below hind quarter of pupil; mouth opening slightly restricted at jaw angles. A short, finely tapered barbel behind symphysis of lower jaw, its length less than half of orbit diameter. Sensory papillae of cephalic-sensory system on dorsal surface of snout well developed; pores on naked underside of head prominent, owing to pale color of pores set in darker skin. Fossa of anterior dermal window shallow and covered with scales; dermal window not black, as in many other species of genus; posterior light organ adjoining vent region ill-defined and poorly developed. Pyloric caeca moderately long, 20 (19 and 24 in two paratypes); ovaries in holotype large, eggs free and probably in or approaching terminal stage.

Premaxillary teeth small, conical, pointed, in broad short bands that occupy less than half length of rictus. Dentary teeth similarly small, in moderate bands that extend posterolaterally beyond rictus.

Branchiostegal membranes broadly attached to isthmus; gill openings extend anteroventrally to a vertical approximately one eye lens behind orbit. Gill rakers tubercular, none on outer side of first gill arch; outer gill slit greatly restricted, its vertical opening greater than barbel length (slightly longer in one paratype).

Body scales densely covered with diminutive, needlelike spinules greatly reclined and arrayed in 10–14 subparallel to slightly divergent rows on larger scales of dorsum ( Fig. 1 C). Scales of parietal, postorbital and lateral nasal ridges small and little modified; supraoccipital scale scarcely developed; median nasal ridge composed of 10 modified platelike scales with short erect spinules. Scales of interorbital region covered with multiple slightly divergent rows of short, needlelike, moderately reclined, closely spaced spinules.

Paired fins relatively short and small; first dorsal fin with slightly prolonged spinous ray; interspace between first and second dorsal fins short, much less than length of first dorsal fin base; fin rays of second dorsal fin high and almost equal in length to opposite rays of anal fin, but usually somewhat more slender. Origin of anal fin far posterior to vertical through origin of second dorsal fin.

Otolith ( Figs. 1 D–E, based on right sagitta otolith taken from holotype). Otolith large (13 mm in diameter), oval in outline with anterior part slightly narrow. Distal surface concave to irregular, proximal surface slightly convex. Dorsal area narrower than ventral area, dorsal depression a narrow band, ventral depression absent. Dorsal, ventral and posterior margins crenate; anterior margin rounded. Sulcus groove moderate, ostium (anterior sulcus) longer than cauda (posterior sulcus); opening ostio-caudal. Colliculum not well-developed. Crista superior and inferior well-developed. Rostrum and antirostrum absent, excisura a small notch, pseudo-excisura absent.

Coloration (in preserved holotype). Overall color of head and dorsum medium brown or grayish-brown; ventral regions generally paler, almost white on tail. Prominent saddlelike bands along length of body, the anteriormost on nape and below anterior half of first dorsal fin, the second below anterior part of second dorsal fin, followed by a prominent narrow (1 or 2 scales wide) pale interspace, then a broad third saddle, behind which saddles less distinct and not extending below lateral line. Two pale interspaces between anterior three saddles directed down and forward; second saddle appears to slant diagonally forward to merge with dark area on abdomen. A pale horizontal streak two or three scales deep and roughly six or seven (four or five) scales wide positioned two scale rows below lateral line and a short distance behind dorsal margin of gill cover. Abdominal and chest regions underlain with blue integument, with faint silvery reflections showing through pale brownish squamation. Naked underside of snout and suborbital/preopercle regions uniformly light brownish, but lips and jaws completely pale. Thin ventral edge of mandible black, but gular region pale, behind which branchiostegal membrane intensely black, with only thin dorsal edge of membrane at tips of uppermost branchiostegals pale. Paired and first dorsal fins black; second dorsal and anal fins dark.

Coloration of a fresh specimen, CAS 224492, is seen in Figure 2 A. The ventral half of the head and body are broadly white to ivory with none of the blue trunk color of the preserved holotype visible. The saddle marks are much more prominent and the distal tips of the first dorsal and pelvic fins appear clear or whitish; the pectoral fin appears clear.

Distribution. Coelorinchus fuscigulus n. sp. appears to be confined to the northeastern coast of Taiwan and the East China Sea on the Diaoyutai Archipelago, due west of Okinawa. Depth range unknown, but likely less than 600 m.

Etymology. From the Latin fuscus, dark, swarthy, and gula, throat, in reference to the blackish branchiostegal membranes.

Comparisons. Coelorinchus fuscigulus sp. nov. falls in that group of species that includes C. brevirostris Okamura in Okamura and Kitajima, 1984, C. cingulatus Gilbert and Hubbs, 1920 , C. cylindricus , C. gladius Gilbert and Cramer, 1897 , C. hubbsi Matsubara, 1936 , C. matsubarai Okamura in Okamura et al., 1982, C.

melanosagmatus Iwamoto and Anderson, 1999 , C. multifasciatus Sazonov and Iwamoto, 1992 , and C. spilonotus Sazonov and Iwamoto, 1992 . Okamura (1984:227) considered “seven species, hubbsi , matsubarai , cingulatus , gladius , acutirostris , brevirostris , and an undescribed species at hand. ” to be members of the C. hubbsi complex of the subgenus Quincuncia . Chiou et al. (2004a: 302–303) subsequently included the other species listed as belonging to this complex. Members of this group all have: (1) a relatively slender, somewhat cylindrical body; (2) sharply pointed snout; (3) high second dorsal fin whose rays are about equal in length to those of the anal fin; (4) short interspace between the dorsal fins; (5) long light organ with a dermal window on the chest distantly separated from the dermal window in front of the anus; (6) underside of head naked except for a narrow margin of scales along anterolateral edge of snout and occasional small scales below junction of infraorbital and preopercle ridges (above angle of lower jaw); (7) nasal fossa naked except along ventral margin; (8) body scales covered with short needlelike to narrowly lanceolate spinules in 5–14 subparallel to slightly divergent rows; and (9) origin of anal fin well posterior to origin of second dorsal fin. Coelorinchus acutirostris Smith and Radcliffe in Radcliffe, 1912 agrees in most of these characters, but it does not have the same elongated body shape of the others, and like C. cylindricus , it has a completely supported anterolateral snout margin, whereas all others have the anterolateral margin incompletely supported.

Coelorinchus fuscigulus is similar to C. cylindricus in body markings and most other external features. In addition to the character of fully supported anterolateral snout margin, the two differ (enumerated in Table 1 ) in several proportional measurements (preoral length, orbit diameter, distance orbit to preopercle, postorbital length of head, length upper jaw, and body depth) and scale row counts. Compared to C. cingulatus , the new species lacks a prominent horizontal dark streak running below the postorbital ridge (along dorsal margin of preopercle and opercle) and a diagonal dark saddle mark below the first dorsal fin that runs down and forward to behind the upper corner of the opercle. The new species also has a darker branchiostegal membrane, and the first dorsal fin is black to the base (but possibly distally paler), as compared to black midlaterally on fin in C. cingulatus ; and the first dorsal lacks a notably prolonged spinous ray. Coelorinchus matsubarai and C.

gladius are readily distinguished from the new species by their large, ocellated black spot above the pectoral fin, and first dorsal fin blackish distally; C. hubbsi has prominent longitudinal stripes along the body; C. brevirostris lacks distinct body markings, has a greatly elongated spinous dorsal ray, and a number of meristic and proportional differences; C. multifasciatus has extensive naked areas atop the snout and head and a shorter abdomen (distance from outer pelvic ray to anal fin origin less than postrostral length); C. spilonotus has first dorsal fin black tipped; C. melanosagmatus has different body markings, a black median stripe connecting the two windows of the light organ, and black-tipped first dorsal fin.

Remarks. The ten members of this loosely defined group (not including C. acutirostris ) fall more or less into the subgenus Quincuncia Gilbert and Hubbs, 1920 , except that none have the characteristic quincunx arrangement of spinules on body scales that was an original diagnostic feature of the taxon. Okamura (1970: 154) expanded and refined the diagnosis of Quincuncia to include: scales with spinules “usually arranged in quincunx order…but sometimes in divergent rows (for example, in C. hubbsi , C. longissimus and partly in C. formosanus ),” “median and lateral processes of nasal bone not united along anterolateral margin of snout,” “snout very long…the anterolateral dorsal surface largely naked (except in C. hubbsi ),” and a number of additional characters. The subgeneric grouping breaks down when all ten members of the Coelorinchus hubbsi complex are included, which suggests that a more-thorough analysis is necessary to properly determine the phylogenetic relationships and clades within the genus Coelorinchus .

Most of the species in this complex are restricted in their geographic distribution, and all are largely oceanic and island-associated. Their relatively long, slender, terete body and well-developed second dorsal fin suggest a more active, off-bottom existence, in contrast to most of its congeners which for the most part are tied close to the bottom. Of these species, C. cingulatus appears to have the most widespread geographical distribution, as it has been reported from Japan south through Taiwan, the Philippines, New Caledonia, Vanuatu, the Loyalty Islands, Wallis and Futuna Islands, and the east coast of Australia to 28°S ( Merrett and Iwamoto 2000: 744); however, Merrett and Iwamoto (loc. cit.) stated that their specimens did not entirely agree with the original description of the species and Iwamoto and Graham (2001: 442) treated their New South Wales ( Australia) specimens as a species that could be compared with C. cingulatus .

Figures

FIGURE 1. Coelorinchus fuscigulus sp. nov., holotype, ASIZP 70169, female, 74.8 mm SL, NE Taiwan, preserved specimen. A. Lateral view of body. B. Dorsal view of head. C. Scanning electron micrograph (SEM) of scale, taken from between first and second dorsal fins. D. Right sagitta otolith, 13 mm in diameter, proximal surface, and E. same otolith, distal surface.

FIGURE 2. Coelorinchus fuscigulus sp. nov. A. ASIZP 70168, paratype, female, 77.1 mm HL, NE Taiwan, preserved specimen. B. CAS 224492, paratype, 45.4 mm HL, Diaoyutai Archipelago, fresh specimen.

Tables

TABLE 1. Comparative data for five species of Coelorinchus. Figures in parentheses are outside the range of most specimens. Figures in square brackets in the fuscigulus column are for the holotype.

Species fuscigulus	brevirostris	cingulatus	hubbsi	matsubarai
No. of specimens 10	8	8	13	8
Total Length (mm) 190–[322]	170+-215+	122-233+	103-275	208+-241
Head Length (mm) 45.4–[74.8]	45.9–53.8	35.1–56.4	25.0–67.3	51–60
Measurement (in % HL)
Snout Length [36]–41	40–44	45–56	41–48	40–49
Preoral Length [30]–34	33–39	34–44	37–44	32–45
Internasal Width [17]–20	19–20	17–21	19–22	17–20
Interorbital Width 20–22[21]	19–22	19–22	21–24	20–23
Orbit Diameter 24–[25]	25–28	22–26	25–29	25–28
Suborbital Height 12–[14]	13–14	13–14	12–14	12–14
Postorbital Length 36–[39]	32–34	27–38	28–32	28–32
Orbit to Preopercle 35–[38]	31–34	29–36	28–32	27–32
Upper Jaw 26–[30]	21–24	21–27	21–26	21–27
Length Barbel [9]–11	4–7	5–10	8–12	9–12
Length 1st Gill Slit 9–16[14]	13–13	10–14	8–13	10–13
Preanal Length 152–[170]	101–171	141–162	140–164	153–177
Outer V to A origin 51–[70]	36–53	37–53	42–60	52–67
Isthmus–A. 82–[104]	84–91	60–80	73–87	79–97
Body depth (great) 50–58[57]	39–48	36–45	37–55	44–50
1D–2D interspace 10–[15]	7–13	8–13	7–16	10–18
Height 1D 52–64[57]	80–127	46–86	53–70	48–60
Length P 40–[45]	39–46	33–43	38+42	39–46
Length V 39–45[46]	37–45	32–46	37–42	35–42
1D base length 18–[23]	15–18	16–24	18–23	19–25
Counts
1D rays (segmented) 8–[9]	(7)8	8–9	9(8)	9–10
P rays (excl. i) 16–[18]	15–19	15–20	(13)17–19	16–18
GR-I (mesial) 1-2+5-7[2+7]	1-3+5-7	1-2+5-6	1-2+6-7	1-2+6-8
GR-II (lateral) 0+5-6[0+6]	0+5	0+5	0+5-6	0+6-7
GR-II (mesial) 1-2+6-7[2+6]	1-2+5-6	1-2+5-7	1-2+6-8	1-2+6-8
Scales below 1D origin [7.5]–8.5	5.0–6.5	5–7	5.5–7.0	5.5–7.5
Scales below 2D origin 6.5–[7.5]	4.5–5.5	4–6.5	4.5–6.5	5.5–6.5
Scales below midbase 1D 5.5–[6.5]	4.5–4.5	4.5–6.5	4.0–5.5	4.5–5.5
Scales on lateral line over distance [28]–34(38) equal to pre1D	27–33	27–28	29–37	33–36