Stolephorus grandis Hata & Motomura, 2021b

Hata, Harutaka, Wibowo, Kunto, Lavoué, Sébastien, Pogonoski, John J., Appleyard, Sharon A. & Motomura, Hiroyuki, 2024, Enhanced data on Stolephorus grandis and Stolephorus waitei (Teleostei: Clupeiformes: Engraulidae), two species endemic to the Sahul Shelf, western Pacific Ocean, Zootaxa 5538 (1), pp. 1-22 : 5-11

Stolephorus grandis Hata & Motomura, 2021b

[English name: Papuan Double-lined Anchovy]

Figure 2 ; Tables 1 , 2

Stolephorus grandis Hata & Motomura, 2021b: 481 , fig. 1 [type locality: Merauke, Papua, Indonesia; paratype localities: Cairns, Queensland and Van Diemen Gulf, Northern Territory, Australia]

Materials examined. 18 specimens, 59.2–116.1 mm SL.

Holotype. RMNH.PISC. 24670, 102.9 mm SL, Merauke , Papua, Indonesia, 5 Apr. 1955.

Paratypes. 9 specimens, 59.2–116.1 mm SL: AMS-I. 22777-006, 59.2 mm SL, south end of Ellis Beach , north of Queensland, Cairns, Australia (16°43′48″S, 145°39′00″E); RMNH.PISC. 84311, 116.1 mm SL, collected with the holotype; KAUM–I. 156158, 82.6 mm SL, NSMT-P 140585, 80.5 mm SL, NTM S. 10071-001 , 5 specimens, 77.7–88.0 mm SL, Van Diemen Gulf , Northern Territory, Australia .

Nontype specimens. INDONESIA: NCIP 3751 , 107.0 mm SL, eastern Indonesia ; TU 170854 , 2 specimens, 77.4–89.3 mm SL, 4 km off estuary of Ajikwa River , Mimika Regency, Central Papua ; TU 178597 , 84.1 mm SL, estuary of Minajerwi River , Mimika Regency, Central Papua . PAPUA NEW GUINEA: CSIRO H 8834-01 (tissue code: BW-A16956, BOLD accession number: FOAQ794-22 ), 106.1 mm SL, Gulf of Papua, east of Fly River mouth (08°34′S, 144°10′E), 12–17 m depth ; CSIRO H 8838-01 , 113.5 mm SL, off Purari, Gulf of Papua (07°54′S, 145°00′E), 13–14 m depth . AUSTRALIA: QM I.16538, 1 of 2 specimens, 95.5 mm SL, beach at Squatters Hut, Murray River , Queensland (18°05′S, 146°00′E) ; QM I.27596, 1 of 10 specimens, 93.0 mm SL, Karumba Point Beach, near Norman River mouth, Queensland (17°27′S, 140°50′E), 0–1.5 m depth .

Materials for distributional records (morphometric and meristic data not collected; 3 specimens: 58–60 mm SL). CSIRO A 1207, 60 mm SL, CSIRO A 1234, 58 mm SL, CSIRO A 1235, 59 mm SL, Repulse Bay, mouth of Proserpine River , Queensland, Australia (20°28′S, 148°42′E) .

Diagnosis. A species of Stolephorus with the following combination of characters: 1UGR 14–17 (modally 16), 1LGR 21–23 (22), 1TGR 35–39 (39); 2UGR 10–12 (11), 2LGR 18–21 (20), 2TGR 28–33 (31); 3UGR 8–10 (9), 3LGR 10–12 (11), 3TGR 18–22 (20); 4UGR 7–9 (8), 4LGR 9–10 (9), 4TGR 16–19 (17); prepelvic scutes 3–6 (4, 5); scale rows in longitudinal series 35–38 (36); transverse scales 8; pseudobranchial filaments 20–27 (24); vertebrae 42–43 (42); paired dark patches on parietal and occipital regions; paired dark lines on left and right on dorsum from occipital region to dorsal-fin origin but absent behind dorsal-fin base; no black spots on suborbital area and tip of lower jaw; predorsal scute absent; no spine on pelvic scute; posterior margin of preopercle rounded, not indented; maxilla comparatively short, 16.7–18.3% of SL (mean 17.7%), its posterior tip slightly short of or slightly beyond posterior margin of preopercle; lower jaw comparatively short, 14.3–15.3% of SL (14.8%); head comparatively short, 22.0–24.0% of SL (23.1%); postorbital length comparatively short, 11.5–12.4% of SL (12.0%); short dorsal-fin base, 12.6–14.8% of SL (14.0%); short anal-fin base, 16.0–17.8% of SL (16.9%); caudal peduncle long, 21.9– 23.7% of SL (22.8%); pelvic fin short, 8.3–9.0% of SL (8.6%), posteriorly not reaching to vertical through dorsal-fin origin when depressed; anal-fin origin located below ninth to twelfth dorsal-fin ray origin; no melanophores on pectoral fin.

Description. Body elongated, subcylindrical, deepest at dorsal-fin origin. Dorsal profile gently elevated from snout tip to dorsal-fin origin, thereafter, gradually decreasing to dorsal contour of central part of caudal peduncle. Ventral profile gently descending from tip of lower jaw to insertion of pelvic fin, thereafter nearly straight (parallel to body axis) to origin of anal fin, subsequently ascending along anal-fin base. Ventral contour of caudal peduncle nearly straight and parallel to body axis. Abdomen rounded, covered with three to six prepelvic scutes. Prepelvic scutes spine-like, retrorse, hard. No scutes on abdomen posterior to pelvic scute. No spine on pelvic scute. Predorsal scute absent. Snout projecting, rounded, positioned lower than upper margin of eye. Orbit elliptical, entirely covered with eyelid. Eye longer than snout, positioned above pectoral-fin insertion. Iris round. Interorbital space flat, narrower than eye diameter. Nostrils paired, positioned close to each other, just anterior to orbit. Mouth large, inferior, almost parallel to body axis, extending backward to posterior margin of orbit. Maxilla rather long, extending posteriorly almost to or slightly beyond posterior margin of preopercle. Lower jaw slender. Mandibular joint located posterior to posterior margin of eye. Uniserial small conical teeth on both jaws. Single (partly biserial) rows of conical teeth on palatines. Several conical teeth present on vomer. Teeth patch formed by fine, densely packed teeth present on pterygoids. Several rows of conical teeth on upper edges of basihyal. Dorsal surface of hyoid arch entirely smooth, but small rough teeth present in parts. Posterior margins of preopercle, subopercle, and opercle rounded (not indented), smooth, without serrations. Pseudobranchial filaments present on inner side of opercle and exposed, not covered with skin (visible without dissection); length of longest filament less than eye diameter. Gill arch four pairs, gill rakers present on anterior surfaces of all gill arches and posterior surface of third gill arch. Gill rakers slender, rough, visible from side of head when mouth open. Gill filaments present on all gill arches. Isthmus muscle long, anteriorly reaching to posterior margin of gill membranes. Urohyal embedded in isthmus muscle, not visible without dissection. Gill membranes on both sides joined distally, most of isthmus muscle exposed (not covered by gill membrane). Branchiostegal rays elongated, entirely covered with gill membrane. Anus situated just before anal-fin origin. Pectoral fin triangular, posterior tip pointed, dorsal, posterior, and ventral margins almost straight; fin insertion slightly posterior to posterior margin of opercle, lower than snout tip; posterior tip not reaching to pelvic-fin insertion; uppermost ray unbranched, others branched. Pelvic fin almost triangular, outer contours almost straight; posterior tip of depressed fin not reaching to vertical through dorsal-fin origin; anteriormost fin ray unbranched, others branched. Dorsal fin nearly triangular, anterior and dorsal profile nearly straight; fin origin located slightly anterior to middle of body; anterior three fin rays unbranched, others branched; first ray tiny. Anal-fin origin located just below 9th to 12th dorsal-fin ray origin; anterior three fin rays unbranched, others branched; first ray tiny; posterior tip of depressed fin not reaching to caudal-fin base. Caudal fin forked, posterior tips of both lobes pointed; anterior and posterior margins of both lobes nearly straight. Head without scales. Fins scaleless, except for broad triangular sheath of scales on caudal fin and elongated sheath of scales on bases of dorsal and anal fins. Body scales completely lost, except for prepelvic scutes.

Coloration of fresh specimens. Based on CSIRO H 8834-01 and CSIRO H 8838-01 frozen for six years before photography ( Fig. 2A, B ). Body milky-white, silver longitudinal band (width subequal or narrower than eye diameter) running through middle part of body from cleithrum to caudal-fin base. Silver band with narrow black margin dorsally. Cheek, opercle, and pectoral-fin axillary scale silver. Snout, maxilla, and pelvic-fin axillary scale transparent. Melanophores densely scattered on snout tip, dorsal margin of gill opening, anal-fin base, middle of caudal-fin base, and dorsal surface of caudal peduncle. Pairs of dark patches on parietal and occipital regions. Paired dark lines on dorsum anterior to dorsal fin, but not posterior to dorsal fin. Posterior margins of scale pockets above silver longitudinal line black. Melanophores scattered along fin rays of dorsal and caudal fins. No melanophores on anterior part of lower margin of caudal fin. Pectoral, pelvic, and anal fins translucent, without melanophores. Iris silver, pupil black.

Coloration of preserved specimens. Body uniformly pale, longitudinal band brownish (sometimes remaining silver) and dorsal margin black. Melanophores scattered on lateral surface of head (upper margin of gill opening and snout tip). Pairs of dark patches on parietal and occipital regions. Paired dark lines on dorsum anterior to dorsal fin, but not posterior to dorsal fin. No melanophores on suborbital area. Melanophores scattered along fin rays of dorsal and caudal fins. No melanophores on pectoral, pelvic, and anal fins, and anterior part of lower margin of caudal fin. Scale pockets on dorsum with black margins.

Distribution. Stolephorus grandis is distributed along the south coast of New Guinea and north coast of Australia (from Van Diemen Gulf, Northern Territory to Repulse Bay, Queensland) ( Hata & Motomura 2021b; this study: Fig. 3 ).

Remarks. Stolephorus grandis was described by Hata & Motomura (2021b) based on ten specimens collected from only three localities, Merauke (New Guinea), Cairns (Queensland), and Van Diemen Gulf (Northern Territory). Eleven additional specimens confirmed in this study suggest that the species may be distributed along the entire southern coast of New Guinea and northern coast of Australia ( Fig. 3 ). Hata & Motomura (2021b) compared S. grandis with three species with double black lines on dorsum, long maxilla with posterior tip just reaching or reaching slightly beyond the posterior margin of the preopercle, and lacking predorsal scute ( Stolephorus mercurius Hata, Lavoué & Motomura, 2021 , Stolephorus multibranchus Wongratana, 1987 , and Stolephorus rex Jordan & Seale, 1926), showing that S. grandis can be distinguished from the other three by having fewer gill rakers (1TGR ≤ 39 in S. grandis vs. 1TGR ≥ 39 in the other three), more vertebrae (42 or 43 vs. 40 or less), longer caudal peduncle (longer than 21.9% of SL vs. shorter than 20.8%), and posterior tip of depressed pelvic fin not reaching to vertical through dorsal-fin origin (vs. beyond vertical through dorsal-fin origin). In this study, these characters showed very similar values to those in Hata & Motomura (2021b) and remain diagnostic. Furthermore, Hata & Motomura (2021b) showed several characters such as lengths of head, postorbital length, maxilla, mandible, pelvic fin, dorsal-fin base, and anal-fin base also can separate S. grandis and at least one of the other three species; the diagnostic value of these characters was also confirmed in this study.

Stolephorus grandis and S. waitei (see below) are divergent from each other by an uncorrected genetic distance of 10.3%. These two species differ from the other 22 species of Stolephorus examined in this study by genetic distances> 10.6%. These COI-based genetic distances, significantly above the commonly accepted intra- versus interspecific threshold of 2–3% ( Hebert et al. 2003), support the respective validity of S. grandi s and S. waitei .

The ML phylogenetic tree ( Fig. 4 ) presents the relationships among 24 species of Stolephorus , including for the first time S. grandis and S. waitei . Overall, the topology of this tree is similar to the most comprehensive phylogenetic tree published so far in Hata et al. (2022c) with incongruences limited to a few deep relationships, such as the relative positions of Stolephorus holodon or Stolephorus continentalis ( Stolephorus oceanicus and Stolephorus brachycephalus examined in Hata et al. [2022c] are not included in our analysis because there are no COI sequences available for these two species). The topological differences between our tree and the tree of Hata et al. (2022c) are the consequence of the use of only the “barcode” fragment of the COI gene to reconstruct our phylogenetic tree whereas Hata et al. (2022c) combined this fragment and the cytochrome b gene to infer their tree. Using only the COI gene is informative to test the taxonomic validity of S. waitei and S. grandis but it provides insufficient signal to reliably resolve relationships among the main lineages of Stolephorus . However, we note that despite the few topological differences observed, the overall hypothesis of Hata et al. (2022c) regarding the evolution of the number of prepelvic scutes in Stolephorus is not modified: the ancestral condition in Stolephorus is six prepelvic scutes with later two reductions, from 6 to 5 prepelvic scutes then from 5 to 4. The number of prepelvic scutes in S. grandis (4) and S. waitei (6) appear to represent two cases of homoplastic changes in Stolephorus : independent reduction from 5 to 4 in S. grandis and secondary reversion from 5 to 6 in S. waitei . Overall, there is an evolutionary trend towards reduction in the number of prepelvic scutes in Stolephorus , although variation among closely related species occurs, such as among the three Australian-New Guinean species ( S. grandis , S. nelsoni , and S. waitei ).

In the phylogeny shown in Fig. 4 , S. grandi s is more closely related to two Australian-New Guinean species, S. nelsoni and S. waitei , than to S. mercurius and S. rex , two species that are more similar in morphology and color ( Hata & Motomura 2021b). These three species ( S. grandis , S. nelsoni , and S. waitei ) are morphologically diverse in features such as maxilla length, coloration, vertebral count, and the condition of teeth on the hyoid arch. Morphological differences between S. grandis and S. waitei are discussed under the Remarks section for S. waitei .

Because fresh coloration of S. grandis was previously unknown ( Hata & Motomura 2021b), this study is the first to report on the fresh coloration. Dark paired lines on dorsum, shown as diagnostic characters of the species by Hata & Motomura (2021b), are clearly distinct in the fresh specimens ( Fig. 2B, 2D ).

No information on biology and habitat of S. grandis has previously been reported. Based on available data, specimens examined were collected from waters shallower than 17 m depth, and some specimens were collected from the estuaries of rivers flowing into the Gulf of Papua or the Queensland coast. Furthermore, specimens of QM I.27596 were caught using a seine net when they were schooling in murky shallow waters at a depth of approx. 0–1.5 m in an inner bay where a river flows (J. Johnson, pers. comm.).

Figures

FIGURE 2. Fresh specimens (frozen for 6 years before imaging) of Stolephorus grandis from Gulf of Papua, Papua New Guinea [(A) lateral and (B) dorsal views of CSIRO H 8834-01, 106.1 mm SL; (C) lateral and (D) dorsal views of CSIRO H 8838-01, 113.5 mm SL] and preserved specimens (E: lateral view of NCIP 3751, 107.0 mm SL, eastern Indonesia; F: dorsal view of head of KAUM–I. 156158, paratype, 82.6 mm SL, Van Diemen Gulf, Northern Territory, Australia).

FIGURE 3. Distributional records of Stolephorus grandis (red circles) and S. waitei (blue triangles), based on specimens examined in this study.

FIGURE 4. Fresh specimen (frozen for 19 years before imaging) of Stolephorus nelsoni from Queensland, Australia (CSIRO H 6548-11, 72.7 mm SL).