Siphamia brevilux, Gon & Allen, 2012

Gon, Ofer & Allen, Gerald R., 2012, 3294, Zootaxa 3294, pp. 1-84 : 22-25

Siphamia brevilux new species

Figure 11; Table 6

Holotype: BPBM 32633 , 22.0 mm, female, Papua New Guinea, Madang Province, off Nagada Harbour, lagoon, Tripod Reef , 5°09.493’S, 145°48.732’E, coral and silty sand, 30 m, rotenone, J.E. Randall, 18 November 1987.

Paratypes: BPBM 40996 , 25.0 mm, female, originally part of BPBM 32633 ; CAS 56570, 3 : 16.0– 16.5 mm, Papua New Guinea, Louisiade Archipelago, Bagman Island, off Disi Village , J.E. McCosker and P. Wing, 14 April 1985 ; CAS 65337, 11.7 mm, Papua New Guinea, Madang Province, off northeast side of Masas Island , just west of passage between Masas and Tab islands, S.G. Poss et al., 13 May 1987 ; CAS 65338, 4 : 15.6–21.9 mm and USNM 298542 , 3 : 15.3–20.45, Papua New Guinea, Madang Province, 300 m south of Wongat Island , 5°14’S, 145°45’E, east slope of reef, 8–17 m, S.G. Poss et al., 15 May 1987 ; AMS I.45071-001, 21.4 mm, BMNH 2009.11 .27.1, 20.0 mm , SAIAB 85933 , 21.9 mm and WAM P.33141-001, 21.0 mm, all females and originally part of CAS 65338 ; MNHN 2009-1669 , 19.6 mm and NSMT-P 96740 , 19.5 mm, both females and originally part of USNM 298542 .

Diagnosis: Dorsal rays VII+I,9; anal rays II,8; pectoral rays 12 (rarely 11 or 13); tubed lateral-line scales 0–2; median predorsal scales 5 (one specimen); total gill rakers 3–5 + 9–11 = 13–15; developed gill rakers 1–2 + 8–10 = 9–11; gill rakers on ceratobranchial 7. Body depth 2.3–2.5 in SL and body width 2.1–2.9 in the depth; eye diameter 2.5–3.05 in head length; first dorsal spine 3.1–7.2 in second spine; second dorsal spine 4.2–5.9, spine of second dorsal fin 3.6–4.4, and second anal spine 3.7–5.4, all in head length; pectoral-fin length 3.9–4.6 and pelvic-fin length 4.4–4.9 in SL; caudal-peduncle length 1.3–1.65 in distance between pelvic spine insertion and anal-fin origin. Preopercular edge weakly serrate around angle, with 2–13 (usually 3–7) minute serrations; preopercular ridge smooth. Tip of light organ on each side of tongue bound by membrane.

Colour in life: unknown.

Colour in alcohol: pale brown with variable amount of small dark dots on upper front part of the body that may extend posteriorly to below origin of second dorsal fin; small dark dots sometimes present on opercle at level of eye, and in front of and below pectoral-fin base; indistinct diagonal cheek mark from ventral edge of orbit to angle of preopercular ridge, its anterior end sometimes wider; a narrow dark line from anterior edge of cheek mark to anterior end of preopercular ridge usually present; ventral edge of preopercular ridge sometimes narrowly blackish; larger specimens with dark dots along branchiostegal rays and on upper limb of first gill arch; pelvic-fin base dark brown; fins pale; peritoneum and intestine with dark brown dots, the latter sometimes dark brown; stomach dusky.

Smallest specimen, CAS 65337, 11.7 mm and largest specimen examined, BPBM 32633 , 25.0 mm, both from Madang Province, Papua New Guinea .

Description: Proportional measurements of the holotype and selected paratypes are given in Table 6. Dorsal rays VII+I,9; anal rays II,8; last soft ray of dorsal and anal fins branched to base; pectoral rays 12 (11–13), two upper and lowermost rays unbranched; pelvic rays I,5, all soft rays branched; principal caudal rays 17, upper and lowermost rays unbranched; upper and lower procurrent caudal rays 6 (6–7); tubed lateral-line scales lost (0–2); vertical scale rows about 23; horizontal scale rows at level of second dorsal fin origin 6; median predorsal scales lost (missing in all paratypes, except one with 5); circumpeduncular scales 12; developed gill rakers 1 + 9 (1–2 + 8–10 = 9–11); gill rakers on ceratobranchial 7; branchiostegal rays 7.

Body deep and compressed, its depth 2.4 (2.3–2.5) in SL and its width 2.1 (2.1–2.9) in depth; head length 2.3 (2.2–2.4) in SL; snout length 7.1 (5.8–8.2) and eye diameter 3.05 (2.5–3.0), both in head length; interorbital space slightly convex, its width 5.2 (5.1–5.8) in head length.

Mouth terminal, oblique and large; maxilla reaching posteriorly to vertical at rear edge of pupil and its posterior (vertical) edge straight (slightly indented in some paratypes); upper jaw length 1.9 (1.8–1.95) and lower jaw 1.7 (1.5–1.6) in head length; both jaws with band of small, conical teeth; upper jaw band with 2 series at symphysis, increasing to about 5 series at middle of jaw; lower jaw band with 3 series at symphysis tapering to 2 series posteriorly; inner series teeth of both jaws enlarged, but symphyseal teeth of lower jaw somewhat larger; vomer and palatines with single irregular series.

Rear nostril almost slit-like, close in front of eye at level of dorsal edge of pupil, its long diameter about 3.0 (2.5–3.0) times in pupil diameter; anterior nostril ovate to round, its long diameter over two thirds of rear nostril’s (almost as long as rear nostril in some paratypes), with slightly raised rim, at level of middle of eye and at about mid-distance from tip of snout to rear nostril.

Preopercular edge with 5 (2–13) minute serrations around angle; preopercular ridge smooth; exposed edge of posttemporal with 1 (2–4) minute points.

Scales large, very thin, soft and easily detached; scales spinoid, those on anterior part of body with few or no spines (most paratypes missing most of their scales); tubed lateral-line scales with vertical line of minute papillae along scale above and below tube, and short horizontal line of papillae along dorsal edge of tube; caudal fin with low scaly sheath of 2–3 scale series across its base; other fins without scales or scaly sheath.

Dorsal-fin origin slightly behind vertical through upper pectoral-fin base; first dorsal spine very small, 4.6 (3.1–7.2) in second spine; second dorsal spine 4.2 (4.2–5.9), and third dorsal spine, longest, 3.2 (3.0–3.8) in head length; spine of second dorsal fin 4.4 (3.6–4.2) and longest dorsal soft ray 2.0 (1.8–2.5) in head length; first anal spine 5.2 (2.8–5.7) in second spine; second anal spine 4.6 (3.7–5.4) and longest anal ray 2.2 (2.2–2.6) in head length; pectoral fin reaching posteriorly almost to anal-fin origin, its length 4.0 (3.9–4.6) in SL; pelvic-fin origin on vertical through upper pectoral-fin base, reaching back close to anus (about three quarters of distance between pelvic and anal fin origins), its length 4.8 (4.4–4.9) in SL; pelvic-fin spine length 1.6 (1.5–1.6) in fin’s length; caudal fin emarginate, 3.2 (3.3–3.9) in SL.

Dorsal profile of head slightly convex; predorsal distance 2.3 (2.2–2.3), preanal distance 1.4 (1.5) and prepelvic distance 2.3 (2.3–2.6) in SL; caudal peduncle depth 1.6 (1.25–1.9) in its length, and the length 1.6 (1.3–1.65) in distance between pelvic-fin base and anal-fin origin; latter distance 3.3 (3.3–3.8) in SL.

Colour in life unknown, but expected to be similar to S. fistulosa and S. senoui .

Colour in alcohol: pale brown with faint, small dark brown dots on predorsal area; dots become more widespread posteriorly below first dorsal fin and on anterior part of body; larger dark dots below and in front of pectoral-fin base; dark cheek mark from lower edge of orbit, above upper corner of maxilla, to angle of preopercular ridge, its anterior end wider; diagonal, narrow dark line from upper corner of maxilla to anterior end of preopercular ridge; dark dots along branchiostegal rays and on throat; upper limb of first gill arch and bases of its gill rakers with small blackish dots; pelvic-fin base dark brown; silvery area in front of pelvic-fin bases bordered by dark dots, and several smaller and darker dots present in middle of this area; fins pale, except pelvic spine and anterior two rays with small dark dots proximally; peritoneum with dense dark dots; intestine dark brown; stomach dusky.

Remarks: See Tables 1–3 for frequency distributions of pectoral rays, lateral-line scales and gill rakers. Spines on the scales appear to increase in number and size posteriorly and are more conspicuous on the dorsal and ventral margins of the caudal peduncle. In some specimens the pectoral fin reaches beyond the anal-fin origin. Specimens larger than 19 mm may have minute blackish dots on the predorsal area, and dark brown dots on the throat and isthmus.

This species is a member of the S. tubulata species group. It differs from all other members of this group in having the lowest number of tubed lateral-line scales ( Table 2) and the shortest light organ ( Fig. 3c); the latter character also distinguishes it from all other member of the genus. If the lateral-line scales are missing (a common condition due to handling damage) it may be difficult to separate from S. fistulosa , S. cyanophthalma , S. senoui and S. tubulata , with which it shares a count of 12 pectoral-fin rays. However, all four are modally different from S. brevilux in their gill-raker counts ( Tables 1, 3). When alive, S. cyanophthalma is easily distinguished by the characteristic blue horizontal lines across its eye. Preserved specimens of the latter species, as well as those of S. fistulosa and S. tubulata , have a longer light organ that, measured from the base of the last anal-fin ray backwards, is 1.25–3.5, 1.9–17.3, and 1.1–7.4 in the caudal peduncle length, respectively, versus 9.7–20.75 in S. brevilux (see Fig. 3c). In addition, S. tubulata has a more slender (depth 2.7–3.1 in SL) and thicker (width 1.65–2.5 in depth) body, shorter pectoral fin (4.9–5.9 in SL), smaller eye and larger interorbital space, 3.0–3.7 and 3.5–4.3 in the head length, respectively. Siphamia tubulata and S. cyanophthalma also have a more slender maxilla, its depth 4.2–5.7 and 4.05–5.6 in the upper jaw length, respectively, versus 3.4–4.1 in S. brevilux . The former species also differs from S. brevilux in having the entire body covered with dark dots and usually several irregular dark marks. It appears that S. senoui is morphologically most similar to S. brevilux . However, the colour of the iris of S. senoui (orange in life and dark brown around the pupil in preservative) is distinctive. Although the live colours of S. brevilux are unknown, the iris of preserved specimens has no trace of the dark brown pigment around the pupil observed in most preserved S. senoui and S. fistulosa , suggesting that it has no orange iris in life. Therefore, the length of the light organ, which is somewhat longer in senoui (see comparison in the next paragraph, and Fig. 3c), is the best character for separating the two species.

The smallest sexually mature female of this species was 11.7 mm with a cluster of enlarged eggs at the anterior end of the gonad. In this female the light organ extended to the base of the fifth anal-fin ray. In a 16.5 mm female with a large gonad and fully developed eggs, the light organ extended to above the base of the last anal-fin ray, and in the largest specimen, a 25.0 mm female, it reached about one scale length beyond this point. By contrast, in a 16.3 mm specimen of S. senoui the light organ reached about 1.5 scales onto the caudal peduncle; in a 15.3 mm and 24.4 S . tubulata it extended over one scale length beyond the end of the anal-fin base and along 75% of the caudal peduncle length, respectively. Siphamia brevilux has the shortest light organ of the genus ( Fig. 3a–c).

This species is currently known only from Papua New Guinea ( Fig. 7) where it was found on coral reefs at depths of 8–30 m.

Etymology: The species is named brevilux (Latin: “short-light”) with reference to the length of its light organ, which is the shortest for the genus and an essential character for separating this species from its nearest relatives.