Chaunax nebulosus, Ho, Hsuan-Ching & Last, Peter R., 2013

Ho, Hsuan-Ching & Last, Peter R., 2013, Two new species of the coffinfish genus Chaunax (Lophiiformes: Chaunacidae) from the Indian Ocean, Zootaxa 3710 (5), pp. 436-448 : 437-442

Chaunax nebulosus n. sp.

English name: Eyespot coffinfish Figs. 1 A–B, 2A–D; Table 1

Holotype. CSIRO H 5200-01 (212 mm SL), north of Monte Bello Islands, Western Australia, 19°36’S, 115°27’E, 245 m, 29 Oct. 1998.

Paratypes. 11 specimens, 106–206 mm SL. AMS I.22807-055 (136 mm SL), North-West Shelf, 175 km north of Port Hedland, Western Australia, 18°32’S, 118°17’E, 200–204 m, 2 Apr. 1982. CSIRO H5196-04 (201 mm SL) and CSIRO H 5196-05 (155 mm SL), north of Dampier Archipelago, Western Australia, 19°09’S, 116°26’E, 220 m, 17 Oct. 1998. CSIRO H 5198-02 (139 mm SL), north of Monte Bello Islands, Western Australia, 19°33’S, 115°37’E, 250 m, 28 Oct. 1998. CSIRO H 6372-05 (105 mm SL), west of Lancelin, Western Australia, 31°00’S, 114°49’E, 393 m, 1 Dec. 2005. CSIRO H 6414-23 (151 mm SL), west of Perth, Western Australia, 31°50’S, 115°01’E, 318 m, 19 Apr. 2006. CSIRO H.6460-01 (117 mm SL), west of Perth, Western Australia, 31°37’S, 114°57’E, 404 m, 19 Nov. 2005. NMMB-P19375 (136 mm SL), same data as CSIRO H 5198-02. NMV A.9641 (2, 106– 170 mm SL), 50 km west of Green Head, 30°0.01’S, 114°27.8’E, 380 m, 8 Feb. 1991. NMV A.9665 (206 mm SL), 35 km north-west of Rottnest Island, Western Australia, 31°55.2’S, 115°10.2’E, 320–850 m, 11 Feb. 1991.

Diagnosis. A member of the C. fimbriatus -species group distinguished from its congeners by its dense covering of minute grayish-green irregular spots, 5 large blackish dorsal markings and a combination of the following characters: 3–6 pairs of spinules bridging each neuromast; modally 14 pectoral-fin rays; mainly 8–9 rakers on second gill arch; illicium long and slender; illicial trough elongate, longer than wide; numerous thin pale cirri with brown tips on esca; gill chamber pale with large blackish patch on inner wall of opercle; peritoneal membrane pale; and lateral-line neuromast distribution: BB'=3–5 (mainly 4), BD=2–3 (2), CD=5–7 (6), FG=3–4 (3), GH=10–12 (10 or 11), BI =29–35.

Description. Morphometric and meristic data are given in Table 1 ; following data summary is provided for holotype and range of all types (if different) in parentheses.

Dorsal-fin rays III, 12 (11–12, 1 with 11); pectoral-fin rays 14 (13–14, 1 with 13); anal-fin rays 7; caudal-fin rays 9. Head length 2.4 (2.3–2.5) in SL; head width 5.5 (4.8–5.6) in SL, 2.3 (1.9–2.3) in HL; pre-dorsal length 1.9 (1.8–2.1) in SL; pre-gill opening length 1.5 (1.5–1.7) in SL; pre-preopercular length 3.7 (3.4–3.8) in SL, 1.5 (1.4– 1.6) in HL; upper jaw 5.2 (4.7–5.6) in SL, 2.1 (2.0–2.2) in HL; illicial length 8.3 (8.3–12.4) in HL; eye diameter 6.6 (5.1–6.6) in HL; post-dorsal fin length 6.4 (5.8–6.4) in SL, 2.6 (2.3–2.6) in HL; post-anus length 3.8 (3.3–4.0) in SL, 1.6 (1.3–1.7) in HL; post-anal fin length 7.0 (6.6–7.8) in SL, 2.8 (2.7–3.1) in HL; caudal peduncle depth 4.3 (4.1–4.7) in HL; caudal-fin length 3.5 (2.9–3.5) in SL, 1.4 (1.2–1.4) in HL.

Head globular, skull elevated above rest of body posteriorly; trunk and tail robust, weakly compressed, tapering posteriorly to caudal-fin base; ventral surface of belly flattened; skin thick, loose and flaccid; interspace between eyes broad, convex; caudal peduncle short. Eyes rounded, directed laterally to dorsolaterally; covered by dermal membrane, broadly connected to adjoining skin, forming clear “window”.

Illicium stout, length subequal to eye diameter; esca depressed, forming a large central plate bearing many thin cirri; second dorsal-fin spine close to illicium, embedded under skin and not detectable externally; third dorsal-fin spine situated at about midpoint of predorsal distance, embedded beneath skin. Illicial trough slender, narrow anteriorly and much broader posteriorly, slightly concave, its length more than twice its width. Origin of soft dorsal fin slightly behind midpoint of body; pectoral fin emerging laterally near midpoint of body, slightly anterior to a vertical through gill opening; pelvic fin on breast, well anterior to pectoral fin; anus situated near posterior fourth of body; anal-fin origin near posterior fifth of body, its tip well short of caudal-fin base when depressed.

Nostrils anterior to eye; anterior nostril surrounded by a fleshy membrane, its posterior part taller than anterior part; posterior nostril a circular depression; mouth wide, superior, its opening nearly vertical; lower jaw robust, protruding slightly in front of upper jaw; maxilla tapering, narrow dorsally, broadly expanded ventrally; blunt symphysial spine on symphysis of lower jaw.

Broad transparent membrane on first gill arch; first ceratobranchial well connected to opercular wall and first epibranchial entirely free of opercular wall; gill filaments present on second to fourth gill arches, two rows of gill filaments in second and third gill arches, single row of gill filaments on fourth gill arch; filaments on inner rows of third and fourth gill arches about two-thirds length of filaments on other arches; inner surface of fourth gill arch completely connected to body. Single row of 12 (11–14) rakers on 1st gill arch, 3 (2–4) on upper limb and 9 (8–10) on lower limb, 8 (8–10) rakers on outer row of 2nd arch, 8 (8–9) rakers on outer row of 3rd arch, and single row of 6 (6–8) rakers on 4th arch.

Interspaces of lateral-line neuromast complex slightly longer than the width of neuromast; 3–6 pairs of short spines bridging each neuromast. Lateral-line neuromast counts: supraorbital (AB) 11 (10–12, mainly 11); premaxillary (AC) 8; upper preopercular (BD) 2 (2–3, mainly 2); infraorbital (CD) 6 (5–6, mainly 6); lower preopercular (DG) 3; mandibular (EF) 6 (4–7, mainly 6); hyomandibular (FG) 3 or 4 (mainly 3); pectoral (GH) 10 or 11 (10–12, mainly 10–11); anterior body proper (BB') 4 (3–5, mainly 4); supratemporal (BB) 6; and body proper ( BI) 29–34 (mainly 31), including 2–3 (mainly 2) on caudal fin.

Dorsal surface covered by simple, stout spinules, except for eye window, lips, distal fifth of dorsal surface and entire ventral surface of pectoral fin, distal half of dorsal surface and entire ventral surface of pelvic fin, entire anal fin and its base, membranes of dorsal fin, anus, and caudal-fin rays. Ventral surface covered by shorter simple spinules. Jaws and body margin along lateral line densely covered with simple, stout cirri; entire dorsal surface covered by scattered simple cirri, relatively dense on supraocular membrane and lower portion of maxilla; cirri on dorsal surface and supraocular membrane accompanied by a strong spinule, taller than those adjacent. Cirri absent from ventral surface.

Coloration. When fresh ( Figs. 1 A–B), reddish pink on most of dorsal surface, including soft dorsal-fin rays, densely covered with minute to very small, irregular, grayish or greenish spots, each covering several to more than 20 spinules; those of lateral body fused into large patches, appearing grayish red; small to large rich red patches scattered over dorsal surface, including illicial trough and illicial stem; five obvious larger dark markings, one at posterior margin of illicial trough, a symmetric pair on each dorsal surface of sphenotic region, extending posteroventrally to cross body lateral line in holotype, and a symmetrical pair at same vertical to slightly behind origin of dorsal fin, below body lateral line and extending anteroventrally; small irregular yellowish spots on dorsal surface of pectoral fin; dense coverage of bright whitish spots and short vermiculations on central cranium; spinule bases pale to grayish. Ventral surfaces paler. Cirri of dorsal surface, jaws and lateral body white. Esca vivid white with deep brown cirri. Eye yellowish pink with a dark blue pupil.

When preserved ( Figs. 2 A–D), dorsal surface, including soft dorsal-fin rays, creamy white to pinkish; densely covered with numerous, very small, grayish spots (each ranging from 1 to several spinule bases in width), some fused to form larger scattered, irregular patches; five larger patches mentioned above becoming grayish; cirri on body transparent; esca with transparent base and brown-tipped cirri; pectoral fin with faded grayish spots, pale on distal margin; ventral surface uniformly pale. Gill chamber pale, with large grayish patch on inner opercular wall; gill arches, buccal cavity, peritoneal membrane and external lining of stomach pale.

Size. Reaches at least 212 mm SL.

Distribution. Known from the upper continental slope off northwestern Australia between longitudes 18° and 32° S. All specimens were collected at depths of 218–380 m, with the exception of a specimen collected from a trawl station covering a 320–850 m depth interval.

Etymology. Derived from the Latin nebula, meaning "cloudy" (more or less), and referring its unique diffuse grayish green colour pattern overlain dorsally with five black spots.

Remarks. Chaunax nebulosus n. sp. can be distinguished from congeners of the C. fimbriatus -species group (sensu Ho & Shao 2010, not Caruso 1989) by its dusky colour pattern overlain with five brownish eye-sized spots on the dorsal surface. It is most similar to C. reticulatus Ho, Roberts & Stewart 2013, but differs in aspects of its color pattern ( Figs. 1–2 , compared to Fig. 3 ) and having mainly 10–11 neuromasts in the pectoral series (GH) (vs. mainly 12). It differs from C. fimbriatus Hilgendorf 1879 mainly in lacking two large white spots on the dorsal surface, and having 6 neuromasts in the infraorbital series (CD) and 3 in the lower preopercular series (DG) (vs. 7 and 4 respectively); and from C. umbrinus mainly in lacking a very fine reticulate pattern and having mainly 6 neuromasts in the infraorbital series and 10–11 in the pectoral series (vs. 7 and 13 respectively).

Figures

FIGURE 1. Chauanx nebulosus n. sp., holotype, CSIRO H 5200 - 01, 212 mm SL, fresh condition. A. Dorsal view. B. Closedup of dorsal surface of head.

FIGURE 2. Chauanx nebulosus n. sp., preserved condition. A. - B. Holotype, CSIRO H 5200 - 01, 212 mm SL. C – D. Paratype, NMMB-P 19375, 136 mm SL. A, C. Dorsal view. B, D. Lateral view.

FIGURE 3. Chaunax reticulatus Ho et al., 2013, non-type, preserved, CSIRO H 355 - 01, 175 mm SL, Tasman Sea.

Tables

TABLE 1. Selected proportional measurements of the two new Chaunax species described in this study.

	C. nebulosus n. sp.		C. africanus n. sp.
	Holotype All types		Holotype Paratype
SL (mm)	212 106–212 (n=12)		227 142
% SL	Mean (Range)	SD
Head length	40.8 41.1 (39.3–43.2)	1.0	43.6 43.7
Head width	18.0 19.0 (17.8–21.0)	0.9	23.8 24.6
Pre-preopercular length	27.4 27.8 (26.2–29.5)	1.0	28.9 29.6
Pre-dorsal length	53.4 52.3 (48.5–56.4)	2.5	50.2 52.1
Pre-gill opening length	65.0 62.9 (60.5–65.0)	1.5	65.2 64.1
Illicial length	4.9 4.1 (3.2–4.9)	0.4	4.4 2.8
Eye diameter	6.2 7.4 (6.2–8.1)	0.7	6.5 7.0
Upper-jaw length	19.1 19.6 (17.9–21.3)	1.0	22.5 21.8
Post-dorsal length	15.7 16.5 (15.7–17.3)	0.5	16.3 17.6
Post-anus length	26.1 28.3 (25.1–30.3)	1.8	35.7 31.7
Post-anal length	14.4 14.1 (12.8–15.2)	0.7	11.5 13.7
Caudal-peduncle depth	9.4 9.3 (8.8–9.9)	0.3	9.7 10.0
Caudal-fin length	28.8 31.0 (28.8–34.0)	1.7	27.8 28.9