Stolephorus celsior, Hata & Motomura, 2021

Hata, Harutaka & Motomura, Hiroyuki, 2021, Two new species of Stolephorus (Teleostei: Clupeiformes: Engraulidae) from the western Pacific, Raffles Bulletin of Zoology 69, pp. 109-117 : 109-114

Stolephorus celsior , new species

[New English name: Rosario Anchovy] ( Fig. 1 ; Tables 1, 2)

Holotype. BMNH 1966.1 .17.93, 60.0 mm SL, Rosario (formerly Salinas), Cavite, Manila Bay, Luzon, Philippines.

Paratypes. 15 specimens, 48.2–64.2 mm SL. BMNH 1966.1.17.94–97, 4 specimens, 56.1–60.4 mm SL, KAUM –I. 146837, 55.8 mm SL, KAUM – I. 146838, 61.0 mm SL, NSMT-P 139183 , 64.2 mm SL, NSMT-P 139184 , 57.4 mm SL, collected with holotype; BMNH 1966.1.17.135–142, 8 specimens, 48.2–57.5 mm SL, same locality as holotype .

Diagnosis. A species of Stolephorus with the following combination of characters: long maxilla, 22.1–23.2% SL (mean 22.6%), its posterior tip slightly short of or just reaching posterior margin of opercle; no predorsal scute; Abbreviations: D–P1 (distance from dorsal-fin origin to pectoral-fin insertion); D–P2 (distance from dorsal-fin origin to pelvic-fin insertion); D–A (distance between origins of dorsal- and anal fins); P1–P2 (distance between insertions of pectoral- and pelvic fins); P2–A (distance between pelvic-fin insertion to anal-fin origin).

pelvic scute without spine; gill rakers 17–19 (modally 18) in upper series on first gill arch, 23–25 (23) in lower series, 40–44 (42) in total; gill rakers 11–13 (12) in upper series on second gill arch, 20–22 (21) in lower series, 32–35 (32) in total; gill rakers 9–11 (10) in upper series on third gill arch, 12 or 13 (12) in lower series, 21–23 (22) in total; gill rakers 8–10 (8) in upper series on fourth gill arch, 10 or 11 (10) in lower, 18–21 (18) in total; gill rakers 5–7 (6) on hind face of third gill arch; prepelvic scutes 4–6 (6); transverse scales 8; pseudobranchial filaments 17–20 (19); paired dark patches on parietal and occipital regions without a following pair of dark lines; numerous black spots on snout and lower-jaw tip, rarely on suborbital area; depressed pelvic fin not reaching to vertical through dorsal-fin origin; snout rather long, 4.0–4.5% SL (mean 4.3%); pectoral fin rather long, 16.6–17.9% SL (17.2%); pelvic fin long, 9.5–10.4% SL (9.8%); head large, 26.0–27.5% SL (26.6%); orbit large, 8.7–9.3% SL (9.0%); lower jaw rather short, 17.9–18.5% SL (18.1%).

Description. Data for holotype presented first, followed by paratype data in parentheses (if different). Counts and measurements, expressed as percentages of SL or HL, given in Tables 1 and 2.

Body laterally compressed, elongate, deepest at dorsal-fin origin. Dorsal profile of head and body gently elevated from snout tip to dorsal-fin origin, thereafter gradually 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 nearly straight and parallel to body axis and ventral profile of body from anal-fin origin to caudalfin base slowly rising. Abdomen rounded, covered with six (four to six) spine-like scutes. Postpelvic and predorsal 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 backward beyond posterior margin of eye. Maxilla long, its posterior tip pointed, just short of or reaching posterior border of opercle. Lower jaw slender. Single row of conical teeth on each jaw and palatines. Small conical teeth patch on pterygoids. Several small conical teeth on vomer. No teeth on dorsal surface of hyoid. 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 margins of preopercle and opercle rounded, smooth. Subopercle with rounded posterior margin. Posterior margin of preopercle slightly concave (moderately concave in some paratypes), indented. Gill membrane without serrations. Interorbital space flat, width less than eye diameter. Pseudobranchial filaments present, longest filament shorter than eye diameter. Gill rakers long, slender, rough, visible from side of head when mouth opened. Isthmus muscle long, reaching anteriorly to posterior margin of gill membranes. Urohyal hidden by isthmus muscle (visible only following dissection). Gill membrane on each side joined distally, most of isthmus muscle exposed (not covered by gill membrane). Head scales and lateral line absent. Fins scaleless, except for broad triangular sheath of scales on central part of both lobes of caudal fin. Dorsal-fin origin posterior to vertical through base of last pelvic-fin ray, slightly posterior to midpoint of body. Dorsal and anal fins with three anteriormost rays unbranched and closely spaced, first ray of both fins minute. Anal-fin origin just below base of eighth (seventh to ninth) dorsal-fin ray. Posterior tip of depressed anal fin not reaching caudal-fin base. Uppermost pectoral-fin ray unbranched, inserted below midline of body. Posterior tip of pectoral fin not reaching vertical through pelvic-fin insertion; pelvic fin shorter than pectoral fin; pelvic-fin insertion anterior to vertical through dorsal-fin base. Posterior tip of depressed pelvic fin not reaching to vertical through dorsal-fin origin.

Colour of preserved specimens. Body uniformly pale ivory with whitish longitudinal band, width slightly less than pupil diameter, from just behind upper opercular margin to caudal-fin base. Pairs of dark patches on parietal and occipital regions. No dark lines on dorsum. Numerous black spots on snout and lower-jaw tip (sometimes on suborbital area). Melanophores scattered on posterior margin of dorsal scale pockets. All fins whitish, semi-transparent. Melanophores scattered along fin rays of dorsal and caudal fins. Live and fresh colouration unknown.

Distribution. Currently known only from the southern part of Manila Bay, Luzon, Philippines (Rosario, Cavite).

Etymology. The specific name celsior , a Latin adjective, refers to the higher gill raker counts in the new species compared to similar species.

Comparisons. The new species is assignable to the genus Stolephorus , as defined by Whitehead et al. (1988) and Wongratana et al. (1999), having a long isthmus muscle reaching anteriorly to the posterior margin of the gill membrane, the urohyal covered by muscle, and prepelvic scutes, in addition to the absence of postpelvic scutes. Stolephorus celsior , new species, differs from all other congeners, except for S. babarani , S. baweanensis , S. bataviensis , and S. concursus , new species (described herein) in having a long upper jaw, its posterior tip beyond the preopercle posterior margin (slightly short of or extending beyond the opercle posterior margin) and numerous dusky spots on the snout and lower-jaw tip ( Whitehead et al., 1988; Wongratana et al., 1999; Kimura et al., 2009; Hata & Motomura, 2018a –d; Hata et al., 2019, 2020a, b, 2021; Gangan et al., 2020; this study). However, S. celsior has a greater number of total gill rakers on each gill arch (e.g., 40–44 on first gill arch in S. celsior vs. 41 or fewer in the other four species; Table 1; Fig. 2A ) and a generally deeper caudal peduncle (10.1–11.1% of SL vs. <10.3%; Table 1; Fig. 3A ). Moreover, the new species differs distinctly from S. bataviensis and S. concursus in having the posterior tip of the depressed pelvic fin not reaching to below the dorsal-fin origin (vs. beyond vertical through dorsal-fin origin). Stolephorus celsior further differs from S. bataviensis in having a longer pectoral fin (16.6–17.9% SL vs. 14.7–16.4%; Table 2; Fig. 3B ) and mandible (17.9–18.5% SL vs. 18.0–20.2%; Table 2; Fig. 3C ), and lower vertebral number (total vertebrae 18–20 + 19 or 20 = 37–39 vs. 20 or 21 + 19–21 = 39 or 40; Tables 1, 3). Detailed comparisons between S. celsior and S. concursus are given under Comparisons of the latter.

Although S. celsior , S. babarani , and S. baweanensis all have the pelvic fin extending to below the dorsal-fin origin, the pectoral fin (16.6–17.9% SL) is longer in S. celsior (vs. <16.8% in the other species; Table 2; Fig. 3B ). Additionally, the pelvic fin (9.5–10.4% SL) is longer (vs. <9.4%; Table 2; Fig. 3D ), and the dorsal-fin origin to pelvic-fin insertion distance (23.5–25.3% SL vs. <24.0%; Table 2; Fig. 3E ) generally greater in S. celsior . The latter also differs from S. babarani in its larger head (26.0–27.5% SL in S. celsior vs. 23.9–25.5% in S. babarani ; Table 2; Fig. 3F ) and orbit (8.7–9.3% SL vs. 7.6–8.4%; Table 2; Fig. 3G ), and longer snout (4.0–4.4% SL vs. 3.6–3.9%; Table 2; Fig. 3H ) and maxilla (22.1–23.2% SL vs. 20.8–22.3%; Table 2; Fig. 3I ). Moreover, the vertebral number in S. celsior tends to be lower than in S. baweanensis (18–20 + 19 or 20 = 37–39 in S. celsior vs. 19 or 20 + 19 or 20 = 39 or 40 in S. baweanensis ; Tables 1, 3).

Figures

Fig. 1. (A) Lateral view of body and (B) dorsal and (C) ventral view of head of holotype of Stolephorus celsior, new species, BMNH 1966.1.17.93, 60.0 mm SL, Rosario, Cavite, Manila Bay, Luzon, Philippines.

Fig. 2. Relationships of total gill-raker numbers (TGR) on (A) first gill arch (1GA), (B) second gill arch (2GA), (C) third gill arch, and (D) fourth gill arch relative to standard length in Stolephorus celsior, new species (triangles), S. concursus, new species (circles), S. babarani (inverted triangles), S. bataviensis (squares), and S. baweanensis (diamonds).

Fig. 3. Morphometrics and meristic of Stolephorus celsior, new species (triangles), S. concursus, new species (circles), S. babarani (inverted triangles), S. bataviensis (squares), and S. baweanensis (diamonds) (all vs. standard length; SL). A, ratio of caudal-peduncle depth to SL; B, pectoral-fin length to SL; C, mandibular length to SL; D, pelvic-fin length to SL; E, distance from dorsal-fin origin to pelvic-fin insertion to SL; F, head length to SL; G, orbit diameter to SL; H, snout length to SL; I, maxilla length to SL.