Siphamia argentea Lachner

Gon, Ofer & Allen, Gerald R., 2012, 3294, Zootaxa 3294, pp. 1-84 : 21-22

Siphamia argentea Lachner

Figure 10

Siphamia argentea Lachner, 1953: 421 , fig. 71 (type locality, north Balabac Strait , Philippines; holotype, USNM 112042 ).

Diagnosis: Dorsal rays VII+I,9; anal rays II,8; pectoral rays 13; tubed lateral-line scales 23–24; median predorsal scales 5–6; total gill rakers 3–4 + 9–10; developed gill rakers 1 (1 of 18 with 2) + 8–9; gill rakers on ceratobranchial 7 (1 of 18 with 8). Body short and compressed, its depth 2.45–2.75 in SL and width 1.95–2.5 in the depth; eye diameter 2.85–3.7 in head length; first dorsal spine 2.1–3.3 in second spine; second dorsal spine 4.6–6.3, spine of second dorsal fin 3.3–4.4 (3 specimens), and second anal spine 4.4–6.0, all in head length; pectoral-fin length 4.2–5.0 and pelvic-fin length 4.5–4.8 in SL; caudal-peduncle length 1.45–1.9 in distance between pelvic spine insertion and anal-fin origin. Preopercular edge with 14–28 serrations; preopercular ridge smooth. Scales strongly spinoid. Tip of light organ on each side of tongue bound by membrane.

Colour in life: unknown.

Colour in alcohol: body brown, frequently with clusters of small dark spots forming blotches above and below middle of body; head may be somewhat paler than body; wide cheek mark, or trace of it, consisting of small dark dots from lower edge of eye to upper angle of maxilla, sometimes continuing to angle of preopercular ridge; narrow dark line may be present under vertical edge of maxilla from its upper corner to anterior end of ventral peropercular ridge; fins pale, but base of pelvic fins with variable amount of dark brown dots; peritoneum, stomach and intestine with fairly dense dark spots, those on the peritoneum larger. Light organ striated.

Smallest specimen examined, NMV A29726 -013, 15.3 mm, from Australia’s northwestern shelf and largest specimen, USNM 112088, 41.8 mm, from Jolo Light, southern Philippines.

Remarks: See Tables 1–3 for frequency distributions of pectoral rays, lateral-line scales and gill rakers. Body scales, except the area associated with the pectoral fin, have their entire posterior edge with spines. Scales under the pectoral fin, and above and below its base usually have spines only on the middle portion of their posterior edge. In one individual (BPBM 26524) the scales above the pectoral base had only few or no spines. The second gill raker of the single specimen (NMV 29721-003) that had two developed gill rakers on the upper limb was only slightly higher than its width and less than half the length of the first raker. One specimen (USNM 268146) had a faded dark spot at the front end of the first and second dorsal-fin base, and at the base of the last dorsal-fin ray. Lachner (1953) observed these spots on the type specimens, but they have apparently faded, as we could not detect them. Lachner (1953) described the body colour of this species as “…uniform light brown above, becoming more silvery and iridescent laterally,” but the holotype has irregular patches of faint dark dots (not shown in his illustration) running along the middle of body to the end of the caudal peduncle that are similar to the pattern observed on our specimens (see above). His other specimens (all Albatross material) must have lost their colour. In some specimens the striation on the light organ appears as vertical or slightly diagonal lines of small dark dots.

Siphamia argentea is a member of the S. tubifer species group. Together with S. jebbi and S. stenotes it differs from all other species of this group in having 13 pectoral-fin rays as opposed to 14–16 ( Table 1). Both S. jebbi and S. stenotes can be distinguished from S. argentea in having an incomplete lateral line ( Table 2) and two developed gill rakers on the upper limb of the first gill arch. They also have a different colour pattern ( Figs. 20c–e, 28f–g, respectively). In addition, S. argentea differs from other species of this group, except S. guttulata , in having two supraneurals. Unlike the other species of the group this species has a colour pattern of irregular dark markings on the body that, in alcohol, resembles that of S. tubulata and, to a lesser extent, S. elongata and S. corallicola . However, the latter three species are members of the S. tubulata species group, and usually have 11–12 pectoral rays ( Table 1) and 6 gill rakers on the ceratobranchial ( Table 3).

Siphamia argentea is known from the Philippines and the northwestern continental shelf of Western Australia ( Fig. 8). It is rare in collections. Station data of the type material (Albatross stations 5137, 5145, 5174, 5182 and 5356) recorded a depth range of 36–104 m and a bottom varying from fine sand and mud to coarse sand, coral and shells. BPBM 26515 was collected on a bottom of Fungia and soft corals, at 32 m, and USNM 268144 was captured at 23 m. The Western Australian specimens (NMV A29721-003 and A29726 -013) were collected with a beam trawl and a benthic sled at 95– 107 m. Fricke (1970) studied the behaviour of Siphamia associated with Astropyga radiata sea urchins in northern Madagascar that he identified as this species. However, we believe his species was either mossambica or tubifer , most likely the former, as we have not come across any specimens with 13 pectoral-fin rays in the southwestern Indian Ocean.

Material examined: PHILIPPINES: Luzon, Batangas , Caban Island , BPBM 26515 , 28.7 mm ; BPBM 26524 , 31.9 mm. North Balabac Strait , USNM 112042 , 40.8 mm (holotype). Palawan , Ulugan Bay , BPBM 28707 , 3 : 24.8–27.9 mm. Off eastern Panay, Antonia Island , USNM 112090 , 25.3 mm (paratype). Bohol Sea, Siquijor Island, USNM 268146 , 36.5 mm. Mindanao , Zamboanga del Norte , USNM 268144 , 34.6 mm. Sulu Archipelago, Jolo Light , USNM 112087 , 34.7 mm ; USNM 112088 , 3 : 30.8–41.8 mm ; USNM 112089 , 2 : 20.6–27.6 mm (all paratypes). WESTERN AUSTRALIA: northwestern continental shelf, north of Heywood Shoal , NMV 29721-003 , 32.2 mm ; NMV A29726 -013 , 2 : 15.3–17.4 mm .