Siphamia stenotes Gon & Allen 2012, new species

Siphamia stenotes new species

Figures 28f–g, 32; Table 13

Holotype: NCIP 6315, 23.9 mm, female, bay off northwestern side of Selat Iris (03° 54.544’S, 134° 09.679’E), Triton Bay, West Papua, Indonesia, 11.5–12 m, clove oil and hand net, G. Allen and M. Erdmann, 24 April 2006.

Paratypes: BPBM 40999, 5: 12.8–17.4 mm, collected with holotype; NCIP 6316, 6: 14.0– 19.7 mm, collected with holotype; SAIAB 96147, 6: 12.3–18.1 mm, collected with holotype; USNM 396981, 7: 12.0– 18.3 mm, Tanjung Soakasekai (03° 57.629’S, 134° 21.283’E), Kayu Merah Bay, West Papua, Indonesia, 45 m, clove oil and hand net, G. Allen and M. Erdmann, 26 April 2006; WAM P.32799-001, 6: 17.2–22.4 mm, collected with holotype.

Diagnosis: Dorsal rays VII+I,9; anal rays II,8 (rarely II,7); pectoral rays usually 13, occasionally 14; tubed lateral-line scales 9–11; median predorsal scales about 4 (missing or incomplete on all specimens); total gill rakers 2+10 (rarely 2+9), all rakers developed. Body ovate, its depth 2.6–3.1 in SL, and body width 2.0– 2.7 in the depth; eye diameter 2.6–3.1 in head length; first dorsal spine 2.8–4.2 in second spine; second dorsal spine 3.5–4.0, spine of second dorsal fin 3.4–4.0, and second anal spine 3.4–5.7, all in head length; pectoral-fin length 4.5–5.0 and pelvic-fin length 4.5–4.8 in SL; caudal-peduncle length 1.1–1.7 in distance between pelvic spine insertion and anal-fin origin. Preopercular ridge smooth, the margin with 7–15 fine serrations concentrated around angle. Vomer with narrow band of small teeth forming v-shape; palatines with narrow band of small teeth. Scales large, thin and deciduous, cycloid on anterior half of body and weakly spinoid on posterior half. Tip of light organ on each side of tongue bound by membrane.

Colour in life (from underwater photos by G.R. Allen): silvery head and translucent body revealing silvery peritoneum; brown stripe, slightly narrower than pupil diameter, from snout to anterior iris and continuing behind eye along middle of side to caudal-fin base, tapering in width on posterior half of body (Fig. 28f); an additional abbreviated stripe dorsally, originating near nostril, passing above eye, following lateral line, and terminating about midway between mid-lateral stripe and origin of second dorsal fin; also faint brown stripe along base of dorsal fins; bioluminescent organ forming posteriorly tapered, silver stripe extending from breast to ventral edge of caudal peduncle; fins translucent.

Colour when fresh (from colour slide by G.R. Allen): similar to live colouration except overall cream to pale pink instead of semitranslucent, upper side with tiny pepper-like melanophores, and faint brownish stripe across middle of preopercle (Fig. 28g); light organ silvery with dark vertical or slanted striations.

Colour in alcohol: generally pale whitish with tiny pepper-like melanophores, most numerous on anterodorsal portion of body; a dark brown mid-lateral stripe, interrupted by eye, from snout to middle of caudal-fin base; interorbital/occipital region dark grey; a faint brown stripe from side of nape to middle of upper side, terminating below origin of second dorsal fin; also faint narrow stripe along base of dorsal fin; prominent silvery luminescent gland along belly, extending on to lowermost part of caudal peduncle, covered by numerous dark striations, its dorsal edge darkly pigmented; fins translucent; palate and dorsal surface of tongue with scattered contracted melanophores; peritoneum covered with large, conspicuous melanophores; stomach and intestine also with dark pigmentation.

Smallest specimen examined, USNM 396981, 12.0 mm and largest specimen, the holotype, 23.9 mm, both from Irian Jaya Barat Province, Indonesia.

Description: Proportional measurements of the holotype and selected paratypes are given in Table 13. Dorsal rays VII+I,9; anal rays II,8 (except II, 7 in one paratype); all dorsal and anal soft rays branched, the last to base; pectoral rays 13 (13–14), all rays unbranched; pelvic rays I,5, all rays branched; principal caudal rays 17, the upper two and lowermost rays unbranched; upper and lower procurrent caudal rays 7 (occasionally 6 on upper base); tubed lateral-line scales 10 (9–11); vertical scale rows 24; horizontal scale rows at level of second dorsal fin origin 6 (6–7); median predorsal scales about 4 (missing in all specimens); circumpeduncular scales 10; gill rakers 2+10 (2+ 9 in one paratype), all rakers well developed; branchiostegal rays 7.

Body depth 2.8 (2.6–3.1) in SL; body width 2.2 (2.1–2.6) in depth; head length 2.4 (2.2–2.5) in SL; snout length 3.6 (4.0–.0), eye diameter 2.8 (2.7–3.1), and interorbital width 4.5 (4.0–4.7), all in head length.

Mouth large, the maxilla reaching a vertical at about rear edge of pupil, the upper jaw length 1.8 (1.8–1.9) in head length; mouth oblique, the gape forming an angle of 40 degrees to horizontal axis of head and body; posterior edge of maxilla very slightly concave; supra-maxilla absent; upper and lower jaws about equal; a relatively broad band of small villiform teeth in upper and lower jaws; a narrow band of small teeth forming a v-shape on vomer and narrow band of tiny conical teeth on palatines. Tongue broad based with fleshy rounded tip, the upper surface with scattered papillae and covered with dark pigment except for pale rounded tip.

Nostril openings in front of centre of eye, vertically ovate, the posterior opening about twice as large as anterior opening; anterior nostril with elevated fleshy rim posteriorly. Largest pores of lateralis system of head as follows: one dorsally at edge of eye, one immediately above posterior nostril, one below anterior nostril, 3–4 at lower edge of preorbital, and several along edge of mandible.

Preopercular margin finely serrate around angle (10 serrations on left side of holotype and 7–15 on paratypes); preopercular ridge smooth. Scales thin and easily shed, mainly cycloid on anterior half or body and spinoid on posterior half. Lateral line inconspicuous, consisting of 10 (9–11, but missing or partially missing on most paratypes) tubed scales anteriorly on upper portion of side. No scales on dorsal and anal fins except a low sheath at base of second dorsal and anal fins; small scales on basal third of caudal fin; no scales on paired fins except pair of large midventral scales at base of pelvic fins.

Origin of first dorsal fin above third lateral-line scale; first dorsal spine slender and very short, 14.0 (10.6–16.0) in head length; second dorsal spine 3.6 (3.4–4.0) in head length; fourth dorsal spine longest (slightly longer than third), 1.9 (1.9–2.7) in head length; second or third dorsal soft ray longest 1.7 (1.5–2.1) in head length; origin of anal fin below base of third dorsal soft ray; first anal spine very short, 10.9 (8.9–13.3) in head length; second anal spine 3.9 (3.4–5.7) in head length; second anal soft ray longest 2.0 (1.7–2.1) in head length; caudal fin forked, its length 1.3 (1.3–1.5) in head length; fourth and fifth pectoral rays longest 1.9 (1.9–2.1 in head length); origin of pelvic fins vertical with upper pectoral-fin base; first pelvic soft ray longest, usually not reaching anus, its length 2.9 (2.8–3.6) in head length.

Colour descriptions: See Diagnosis above.

Remarks: See Tables 1–3 for frequency distributions of pectoral rays, lateral-line scales and gill rakers. This species is a member of the S. tubifer species group. It is possibly most closely allied to S. argentea that also possesses 13 pectoral rays. Siphamia stenotes and S. jebbi are the only members of this species group with two developed gill rakers on the upper limb of the first gill arch (Table 3). However, S. jebbi differs from S. stenotes in having fewer tubed lateral-line scales and modally higher number of developed gill rakers, while S. argentea has more tubed lateral-line scales and fewer gill rakers (Tables 2, 3). In addition, both S. argentea and S. jebbi lack body stripes, and the latter is a small species barely exceeding 22 mm.

This species is currently known only from the Triton Bay area of West Papua Province (western New Guinea), Indonesia (Fig. 6). Specimens were collected at two sites on small rocky outcrops surrounded by mainly sandrubble bottom at depths between 11.5– 45 m. Most individuals were collected/observed in 11.5–12 m around an unidentified crinoid. The species is possibly an obligate commensal of crinoids, although further observations are required. Approximately 40 fish were seen among the arms or in close proximity of the 30-cm tall crinoid.

Etymology: The species is named stenotes (Greek: “narrowest”) with reference to its dark body stripes, which are the narrowest of any of the striped species in the genus.