Siphamia elongata Lachner

Gon, Ofer & Allen, Gerald R., 2012, 3294, Zootaxa 3294, pp. 1-84 : 36-37

Siphamia elongata Lachner

Figures 14d, 17

Siphamia elongata Lachner, 1953: 419 , fig. 70 (type locality, Canmahala Bay , between Burias and Luzon, Philippines; holotype, USNM 112045 ).

Diagnosis: Dorsal rays VII+I,9; anal rays II,8; pectoral rays 11–12; tubed lateral-line scales 17–23, last 1–4 scales sometimes partially tubed or pitted; median predorsal scales 5; total gill rakers 2–3 + 8–11 = 11–14; developed gill rakers 1 (1 of 19 with 2) + 7–8; gill rakers on ceratobranchial 6 (1 of 19 with 7). Body depth 2.7–3.3 in SL and body width 1.8–1.9 in the depth; eye diameter 2.9–3.7 in head length; first dorsal spine 2.9–3.5 in second spine; second dorsal spine 3.35–4.3, spine of second dorsal fin 3.9–4.6, and second anal spine 4.0–4.9, all in head length; pectoral-fin length 6.0 (2 specimens) and pelvic-fin length 4.5–5.0 in SL; caudal-peduncle length 1.1–1.4 in distance between pelvic spine insertion and anal-fin origin. Posterior preopercular edge with 11–27 (usually 14–23) serrations; preopercular ridge smooth. Scales weakly spinoid. Palatines with a single series of small teeth. Tip of light organ on each side of tongue bound by membrane.

Colour in life (from underwater photos by G.R. Allen): translucent brown with irregular dark brown marks or blotches along middle of body that sometimes merge into poorly defined mid-body stripe; variable amount of dark brown pigment scattered on body, mainly on snout, occiput, around and on anterior base of fins, and along ventral part of body; variable white or silvery reflecting markings scattered on body, sometimes penetrating between midline dark brown blotches and on proximal part of fins; dark brown spot at caudal-fin base frequently overlapping with posterior dark blotch, but is discernible as cluster of darker melanophores.

Colour in alcohol: body pale brown to brown, covered with small dark brown dots frequently forming several irregular dark blotches midlaterally on body; scattered dark dots sometimes present on opercle and below eye; fins pale, but pelvic fins sometimes with small dark dots on proximal part; large, ovate dark spot on caudal–fin base usually present; peritoneum with dark dots of various sizes; intestine and stomach with dark dots. Lachner (1953) described “a diffuse brownish nearly vertical bar below the eye.”

Smallest specimen, 16.0 mm, and largest specimen examined, 34.6 mm, both in USNM 112099, from the type locality.

Remarks: See Tables 1–3 for frequency distributions of pectoral-fin rays, lateral-line scales and gill rakers. The majority of the specimens examined were missing most scales. The count of predorsal scales above is based on two specimens with a full complement of these scales. The serrations of the preopercular edge may be minute and difficult to see without magnification; those on the ventral part can be wide apart and usually do not extend to the anterior half of the ventral edge of this bone. In two specimens the genital papilla was large, over 50% of the length of the first anal-fin spine. In the smallest fish (16.0 mm) the light organ reached posteriorly to about two thirds of the length of the caudal peduncle. In specimens 21.0 mm or larger it ended just before the first procurrent caudalfin ray. The dark, ovate spot on caudal-fin base may be indistinct if its melanophores are contracted, and it may be absent in older, faded specimens.

Siphamia elongata is a member of the S. tubulata species group. It is very similar to S. corallicola which has 0–12 tubed lateral line scales; see Remarks for S. corallicola above for additional differences. The number of developed gill rakers of S. cuneiceps is modally different from that of S. elongata (see Remarks for the former species for additional distinguishing characters). Although S. elongata and S. tubulata share a similar count of tubed lateral-line scales, these two species are modally different in the number of pectoral-fin rays and gill rakers ( Tables 1–3). Moreover, S. tubulata does not have the large, ovate dark spot found on caudal-fin base of S. elongata . The low pectoral-fin ray count and the relatively high number of lateral line scales distinguish this species from all other members of the S. tubulata species group.

Smallest mouthbrooding male was 23.5 mm and smallest female with mature eggs was 24.5 mm ( Lachner 1953). Lachner also found sexual dimorphism in size and body form. Females attained a larger size, had a more elongate body, narrower interorbital space and a deeper caudal peduncle. See also Remarks for the genus Siphamia above.

This species is known only from the Philippines ( Fig. 7) and is rare in collections. A fish collected recently in Brunei is provisionally identified as a member of this species, but with counts of 15 lateral-line scales and 13 serrations on the preopercle edge this fish is intermediate to S. elongata and S. corallicola . While the holotype and most paratypes were captured between 3–50 m on sand and coral bottom one paratype (USNM 112098) was taken at over 300 m, presumably in a trawl, on a bottom dominated by Globigerina .

Material examined: BRUNEI: Muara District, Pelong Pinnacle , SAIAB 87399 , 17.2 mm . PHILIPPINES: Ragay Gulf , USNM 112045 , 34.3 mm (holotype) ; USNM 112099 , 28 : 16.0- 34.6 mm (paratypes) . Luzon, Sorsogon, fish market, USNM 374478 , 2 : 21.0– 23.9 mm. Palawan, Talawtawan, WAM P.33001-001, 11: 16.0– 25.5 mm. Ulugan Bay , BPBM 40998 , 3 : 16.9–26.2 mm (originally part of BPBM 28707 ) . Off northern Mindanao, Tagolo Light , USNM 112098 , 30.3 mm (paratype) . Sulu Archipelago, Jolo Light , USNM 112096 , 22.7 mm and USNM 112097 , 31.2 mm (paratypes) . Sibutu Island , USNM 112095 , 23.8 mm (paratype) .