Stolephorus eclipsis, Hata & Lavoué & Motomura, 2022

Hata, Harutaka, Lavoue, Sebastien & Motomura, Hiroyuki, 2022, Description of three new species previously identified as Stolephorus bengalensis (Dutt & Babu Rao, 1959) or Stolephorus insularis Hardenberg, 1933 and a re-description of S. bengalensis (Chordata, Osteichthyes, Clupeiformes, Engraulidae), ZooKeys 1121, pp. 145-173 : 145

Stolephorus eclipsis sp. nov.

[New English name: Eclipse Anchovy] Fig. 9

Holotype.

MZB 26452, 40.3 mm SL, Bintan Island, Riau Archipelago, Indonesia.

Paratypes.

28 specimens, 32.0-43.7 mm SL. LBRC-F 5039, 35.4 mm SL, LBRC-F 5040, 35.3 mm SL, LBRC-F 5041, 36.1 mm SL, Tanjungpinang, Bintan Island, Riau Archipelago, Indonesia; MZB 26440, 32.0 mm SL, MZB 26441, 36.1 mm SL, MZB 26442, 35.1 mm SL, MZB 26443, 34.7 mm SL, MZB 26444, 34.5 mm SL, MZB 26445, 36.3 mm SL, MZB 26446, 36.2 mm SL, MZB 26447, 38.8 mm SL, MZB 26448, 39.2 mm SL, MZB 26449, 37.7 mm SL, MZB 26450, 40.0 mm SL, MZB 26451, 36.8 mm SL, 26453, 36.4 mm SL, MZB 26454, 39.0 mm SL, MZB 26455, 41.3 mm SL, MZB 26456, 43.7 mm SL, MZB 26457, 39.8 mm SL, MZB 26458, 40.7 mm SL, MZB 26459, 43.2 mm SL, MZB 26460, 43.7 mm SL, MZB 26461, 5 specimens, 38.3-42.4 mm SL, collected with the holotype.

Diagnosis.

A species of Stolephorus with the following combination of characters: 1UGR 19-21 (modally 20), 1LGR 26-30 (28), 1TGR 47-51 (47); 2UGR 13-16 (14), 2LGR 24-27 (25), 2TGR 37-42 (39); 3UGR 10-13 (12), 3LGR 14-16 (15), 3TGR 25-28 (27); 4UGR 8-11 (9), 4LGR 11-13 (12), 4TGR 19-24 (21); prepelvic scutes 5-7 (6); total vertebrae 38-39 (39); long maxilla, posterior tip just reaching or slightly short of posterior margin of opercle; predorsal scute present; pelvic scute without spine; body scales deciduous; posterior border of pre-opercle concave, indented; paired dark patch on parietal area with little following pigmentation; distinct double pigment lines along dorsum posterior to dorsal fin; black spots below eye and on lower-jaw tip absent; anal-fin base short, 17.6-19.3% (mean 18.6%) of SL; third dorsal-fin ray 16.5-18.8% (17.6%) of SL; pelvic fin short, 8.7-9.9% (9.4%) of SL, its posterior tip usually not reaching to vertical through dorsal-fin origin when depressed; distance between posterior ends of supramaxilla and maxilla 4.7-5.4% (5.1%) of SL; pre-dorsal-fin length 51.3-54.9% (53.4%) of SL; dorsal-fin base short, 13.1-14.5% (13.8%) of SL.

Description.

Data for holotype presented first, followed by data for paratypes in parentheses (if different). Counts and measurements, expressed as percentages of SL or HL, given in Tables 5 and 6 . Body laterally compressed, elongate, deepest at dorsal-fin origin. Dorsal profile of head and body slightly convex from snout tip to dorsal-fin origin, gently lowering to uppermost point of caudal-fin base. Ventral profile of head and body slightly convex from lower jaw tip to pelvic-fin insertion, thereafter, slowly rising to lowermost point of caudal-fin base. Single spine-like scute just anterior to dorsal-fin origin. Abdomen somewhat rounded, covered with six (five to seven) spine-like prepelvic scutes. Pelvic scute without spine. Postpelvic scutes absent. Anus just anterior to anal-fin origin. Snout tip rounded; snout length less than eye diameter. Mouth large, inferior, ventral to body axis, extending backwards beyond posterior margin of eye. Maxilla long, its posterior tip pointed, just reaching (or slightly short of) opercle posterior margin. Lower jaw slender. Single row of conical teeth on both jaws and palatine. Patch of fine conical teeth on pterygoid. Several distinct conical teeth on vomer. Several rows of conical teeth on upper edges of basihyal and basibranchial. Eye large, round, covered with adipose eyelid, positioned laterally on head dorsal to horizontal through pectoral-fin insertion, visible in dorsal view. Pupil round. Orbit elliptical. Nostrils close to each other, anterior to orbit. Posterior margin of pre-opercle concave, indented. Subopercle and opercle with smoothly rounded posterior margins. Gill membrane without serrations. Interorbital space flat, width less than eye diameter. Pseudobranchial filaments present, length of longest filament less than eye diameter. Gill rakers long, slender, rough, visible from side of head when mouth opened. Single row of asperities on anterior surface of gill rakers. Isthmus muscle long, reaching anteriorly to posterior margin of gill membranes. Urohyal hidden by isthmus muscle, not visible without dissection. Gill membrane on each side joined distally, most of isthmus muscle exposed, not covered by gill membrane. Body scales deciduous, completely lacking on specimens, except for prepelvic scutes. Head scales absent. Fins scaleless, except for broad triangular sheath of scales on caudal fin. Dorsal-fin origin posterior to vertical through base of last pelvic-fin ray, slightly posterior to middle of body. Dorsal and anal fins with three anteriormost rays unbranched. First dorsal- and anal-fin rays minute. Anteriormost three rays of both dorsal and anal fins closely-spaced. Anal-fin origin just below base of eighth (eighth to eleventh) dorsal-fin ray. Posterior tip of depressed anal fin not reaching caudal-fin base. Uppermost pectoral-fin ray unbranched, inserted below body axis. Posterior tip of pectoral fin not reaching to pelvic fin insertion. Dorsal, ventral and posterior margins of pectoral fin nearly linear. Pelvic fin shorter than pectoral fin, insertion anterior to vertical through dorsal-fin origin. Posterior tip of depressed pelvic fin not reaching to vertical through dorsal-fin origin (reaching to vertical through first to third dorsal-fin ray origin in some paratypes). Caudal fin forked, posterior tips pointed.

Colour of preserved specimens.

Body uniformly pale ivory. A pair of distinct dark patches on parietal region, with little pigmentation on occipital area. Double pigmented lines dorsally posterior to dorsal fin. A few melanophores scattered anteriorly on snout. No black spots below eye and on lower-jaw tip. Melanophores scattered along bases of dorsal and anal fins. All fins transparent, melanophores scattered along fin rays of caudal fin and anterior parts of dorsal and anal fins.

Distribution.

Stolephorus eclipsis sp. nov. is currently known only from Bintan Island, Riau Archipelago, Indonesia (Fig. 4 ).

Etymology.

The specific name " eclipsis " refers to eclipse, reminiscent of the concave pre-opercle of the new species.

Comparisons.

The new species differs from S. bengalensis , S. diabolus and S. eldorado in having higher gill raker counts [1TGR, 47-51 or more in S. eclipsis (vs. 47 or fewer in the other three species); 2TGR, 37-42 in S. eclipsis (vs. 39 or fewer); 3TGR, 25-28 in S. eclipsis (vs. 27 or fewer); and 4TGR, 19-24 in S. eclipsis (vs. 22 or fewer) (Fig. 7 )], a shorter anal-fin base (17.6-19.3% of SL in S. eclipsis vs. 19.0-21.3% in S. bengalensis , 19.8-22.3% in S. diabolus and 19.0-22.3% in S. eldorado ; Fig. 8C ) and pelvic fin [8.7-9.9% (mean 9.4%) of SL in S. eclipsis vs. 9.4-11.0% (10.2%) in S. bengalensis , 9.6-11.3% (10.0%) in S. diabolus and 9.1-11.0% (10.0%) in S. eldorado ; Fig. 8D ] and shorter distance between the posterior ends of the supramaxilla and maxilla [4.7-5.4% (5.1%) of SL in S. eclipsis vs. 5.3-6.6% (5.8%) in S. bengalensis , 5.7-6.4% (6.1%) in S. diabolus and 5.0-6.3% (5.6%) in S. eldorado ; Fig. 8E ]. Stolephorus eclipsis also differs from S. bengalensis in having a shorter third dorsal-fin ray (16.5-18.8% of SL in S. eclipsis vs. 18.5-19.9% in S. bengalensis ; Fig. 8B ) and lower total vertebral number [38-39 (modally 39) vs. 40 or 41 (40) (Table 4 )]. Moreover, S. eclipsis is distinguished from S. diabolus by a greater pre-dorsal-fin distance [51.3-54.9% (mean 53.4%) of SL in S. eclipsis vs. 51.3-52.9% (52.1%) in S. diabolus ; Fig. 10A ] and shorter dorsal-fin base (13.1-14.5% of SL vs. 13.9-16.6%; Fig. 10B ) and postorbital head length (11.5-12.9% of SL vs. 12.8-14.2%; Fig. 10C ).

Figures

Figure 4. Map of the northern part of the Indo-West Pacific region showing distributional records of Stolephorus bengalensis (red circles), S. diabolus (yellow squares) sp. nov., S. eclipsis (green diamond) sp. nov. and S. eldorado (blue triangles) sp. nov., based on specimens examined in this study. Land masses outlined with black lines.

Figure 7. Relationships of total gill raker numbers (TGR) on A first gill arch (1 GA) B second gill arch (2 GA) C third gill arch (3 GA) and D fourth gill arch (4 GA) to standard length in Stolephorus bengalensis (red circles), S. diabolus sp. nov. (yellow squares), S. eclipsis sp. nov. (green diamonds) and S. eldorado sp. nov. (blue triangles).

Figure 8. Relationships of A orbit diameter (as % of standard length; SL) B third dorsal-fin ray length (as % of SL) C anal-fin base length (as % of SL) D pelvic-fin length (as % of SL) and E distance between posterior ends of supramaxilla and maxilla (SMX-MX) in Stolephorus bengalensis (red circles), S. diabolus sp. nov. (yellow squares), S. eclipsis sp. nov. (green diamonds) and S. eldorado sp. nov. (blue triangles).

Figure 9. A lateral B dorsal and C ventral views of preserved holotype of S. eclipsis sp. nov., MZB 26452, 40.3 mm SL, Bintan Island, Riau Archipelago, Indonesia. Scale bars indicate 2 mm.

Figure 10. Relationships of A pre-dorsal-fin length (as % of standard length; SL) B dorsal-fin base length (as % of SL), and C postorbital length (as % of SL) in Stolephorus diabolus sp. nov. (yellow squares) and S. eclipsis sp. nov. (green diamonds).