Chuanax brachysomus, Ho & Satria, 2015

Ho, Hsuan-Ching, Kawai, Toshio & Satria, Fayakun, 2015, Species of the anglerfish genus Chaunax from Indonesia, with descriptions of two new species (Lophiiformes: Chaunacidae), Raffles Bulletin of Zoology 63, pp. 301-308 : 305-306

Chuanax brachysomus sp. nov.

New English name: Short-body frogmouth

( Fig. 3 A–C; Tables 1 , 2)

Holotype. HUMZ 193943 (1, 177), Baruna Jaya IV, st. 67, 2°51.8’N, 95°5.3’E, 2°50.9’N, 95°4.3’E, off Sumatra, 519–581 m, 13 June 2005.

Diagnosis. A species of the Chaunax abei -group with uniform pink body when fresh, mixture of broad-based and narrowbased spinules on ventral surface and combination of the following characters: pectoral-fin rays 13; large head, head length 44.4% SL and width 20.5% SL; short tail (tail length 1=24.2% SL, tail length 2=16.0% SL and tail length 3=14.4% SL); nine rakers on second gill arch; and 12 or 13 lateral line neuromasts in pectoral series and 33 in lateral-line proper.

Description. Morphometric and meristic details are given in Table 1 .

Dorsal-fin rays III, 12; pectoral-fin rays 13; anal-fin rays seven; caudal-fin rays nine. Head length 2.3 in SL; head width 4.9 in SL and 2.2 in HL; pre-dorsal length 1.8 in SL; pre-gill-opening length 1.6 in SL; pre-preopercular length 3.3 in SL and 1.5 in HL; upper jaw 4.2 in SL, 1.9 in HL; illicial length 10.4 in HL; eye diameter 5.2 in HL; post-dorsal-fin length 6.3 in SL and 2.8 in HL; post-anus length 4.1 in SL and 1.8 in HL; post-anal-fin length 6.9 in SL and 3.1 in HL; caudal-peduncle depth 4.6 in HL; caudal-fin length 3.5 in SL and 1.6 in HL.

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

Illicium relatively slender, its length less than eye diameter; esca depressed, forming a large central plate with many pale cirri, many of these with brown tip; 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 oval, slightly concave, posterior half slightly broader than anterior half, its length about 1.3 times its width. Origin of soft dorsal fin slightly behind middle of body; pectoral fin emerging laterally near middle of body, slightly anterior to vertical through gill opening; pelvic fin on breast, well anterior to pectoral fin; anus situated about three-fourths of way along body; anal-fin origin about four-fifths of way along body, tip nearly reaching caudal-fin base when depressed.

Both nostrils anterior to eye; anterior nostril surrounded by 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 symphyseal 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 it; gill filaments present on second to fourth gill arches, two rows of gill filaments on 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 14 rakers on first gill arch, five on upper limb and nine on lower limb, nine rakers on outer row of second arch, 10 rakers on outer row of third arch, and single row of seven rakers on fourth arch.

Distance between lateral-line neuromast complex slightly longer than width of the complex; three or four (mainly three) pairs of short spines bridging each neuromast. Lateral-line neuromast counts: supraorbital (AB) 11; premaxillary (AC) eight; upper preopercular (BD) two; infraorbital (CD) six; lower preopercular (DG) three; mandibular (EF) six; hyomandibular (FG) three; pectoral (GH) 13 on right side/12 on left side; anterior lateral-line proper (BB’) four; supratemporal (BB) six; and lateral-line proper (BI) 33, including three or four on caudal fin.

Dorsal surface covered by simple, moderately slender spinules, except on eye window, lips, distal fifth of dorsal surface and entire ventral surface of pectoral fin, distal half of dorsal surface, entire ventral surface of pelvic fin, entire anal fin and its base, and membranes of dorsal fin, anus, and caudal-fin rays. Dermal spinules mixed with dense narrow-based and scattered broad-based spinules, the last easily seen by the contraction of its colouration without magnification, e.g., more transparent than the rest. ( Fig. 2C ). Narrow band of 4 irregular rows of spinules in front of illicial trough. Squamation on ventral surface similar to that on dorsal surface, but spinules shorter and mostly straight. Jaw and body margins along lateral line densely covered with simple, stout cirri; cirri absent from head, jaws and ventral surface.

Colouration. Uniformly pink when freshly dead; uniformly creamy white when preserved.

Distribution. Represented only by the holotype collected from off Sumatra at depth 519– 581 m. Etymology. The specific name is combination of two Greek words, brachys short and soma body, referring to its relatively short and stout body.

Comparison. Chaunax brachysomus sp. nov. is one of four Chaunax species that have a uniformly pink or red colour when fresh and are uniformly pale when preserved, the other three species being C. russatus , C. mulleus and C. apus (long-term preservation may cause loss of colour pattern in other species as well). It can be easily distinguished from the above-mentioned species by its large head, short tail, and few gill rakers (see Table 2 for detailed comparison).

Although C. nudiventer was characterised by its large irregular greenish spots ( Ho & Shao, 2010), some individuals were found to be uniformly pinkish (Ho, pers. obser.). It differs from C. brachysomus sp. nov. in having a large naked area on the ventral surface and relatively more lateral-line neuromasts in the lateral-line proper (39–57, vs. 33 in C. brachysomus ), upper preopercular series (three to five, vs. two), and pectoral series (15–17, vs. 12 or 13).

The presence of mixed broad- and narrow-based spinules on the dorsal surfaces is common in members of Chaunax . These broad-based spinules are usually difficult to see without magnification, except for these pinkish species which have contract colouration among these two forms of spinules (e.g., more transparent, compared to these narrow-based spinules which are creamy white) and are easy to see. Thus far, C. brachysomus sp. nov. is the only member with mixed broad- and narrow-based spinules on the ventral surface. All other Chaunax species are either naked in this region or have uniformly short spinules.

Figures

Fig. 3. Chauanx brachysomus sp. nov., holotype, HUMZ 193943, 177 mm SL.A, fresh colour after freezing, lateral view.B, preserved, lateral view. C, ventral surface of abdomen showing squamation (anterior to left). Photo by T. Kawai (A) and H.-C. Ho (B, C).

Fig. 2. Chaunax gomoni sp. nov.. A. holotype, HUMZ 193991, 174 mm SL, lateral view, preserved. B. paratype, BMNH 1986.9.29.18, 134 mm SL, dorsal view, preserved. Photo by H.-C. Ho.