Parascombrops pellucidus Alcock, 1889

Schwarzhans, Werner W. & Prokofiev, Artem M., 2017, Reappraisal of Synagrops Günther, 1887 with rehabilitation and revision of Parascombrops Alcock, 1889 including description of seven new species and two new genera (Perciformes: Acropomatidae), Zootaxa 4260 (1), pp. 1-74 : 45-48

Parascombrops pellucidus Alcock, 1889

Figs. 7I , 10A , 13I , 15A – F, 24, 25, 36, Tables 2–7

Parascombrops pellucidus Alcock, 1889: 296 , pl. 22, fig. 1 (syntypes: ZSI 11829, F12437; Bay of Bengal, 6 miles east of Mahanaddi Delta , 20°18’N, 90°50’E, 120 m).

Synagrops pellucidus: Prokofiev & Schwarzhans, 2015: 83 .

Synagrops adeni Kotthaus 1970: 74 , figs. 258–259 (holotype: ZMH 5055 ; Gulf of Aden, 12°25’N, 43°54.5’E to 12°26’N, 43°52’E, Meteor : stn 54, 60 m).

Synagrops adeni: Heemstra 1984 : ACRO Syn 1 (no pagination); Javadzadeh et al., 2012: 495; Prokofiev & Schwarzhans, 2015: 83.

Material examined (47 specimens). BMNH 1890.7.31.13-15, 3 specimens, 69–85 mm SL, 18°30'N, 84°36'E; BMNH 1903.7.8.12-13, 2 specimens, 69–71 mm SL, 24°59’N, 60°58’E; BMNH 1939.5.24.880-891, 9 specimens, 62.5–66.5 mm SL, Murray Expedition : stn 16, off Somalia, Gulf of Aden, 186 m ; BMNH 1939.5.24.892-894, 3 specimens, 77–87 mm SL, Murray Expedition : stn 75, off Oman, Gulf of Oman, 210 m ; USNM 229551, 91.5 mm SL, 29°04’N, 34°45’E, 1450 m; USNM 385248, 7 specimens, 46–59.5 mm SL, 17°43’N, 71°32’E, 90 m; USNM 392727, 10 specimens, 54.5–87 mm SL, 24°55’N, 61°10’E, 192 m; USNM 44428, 6 specimens, 61.5–67.5 mm SL, Bay of Bengal, 179–187 m ; ZMH 8717, paratype of Synagrops adeni , 65 mm SL, 09°40’N, 75°38’E. ZMH 5055, holotype of Synagrops adeni , 53 mm SL, 12°25’N, 54°05’E; ZMH 5056, 2 paratypes of S. adeni , 60–61 mm SL, 12°25’N, 54°05’E; ZMH 5057, 2 paratypes of S. adeni , 55–67 mm SL, 01°18’N, 41°56’E.

Diagnosis. Moderately slender-bodied species with slightly convex dorsal head profile. Anal fin II + 7. Pectoral fin with 14–16 rays, pectoral length 27.1–30.9% SL, reaching anterior edge of anal fin. Gill rakers 19–25. Pseudobranchial filaments 16–26. First anal-fin pterygiophore long, straight, slender, with rather sharp tip and not hollow. Palatines and ectopterygoids narrow, usually with 1, rarely 2 rows of denticles. Orbital diameter 10.1–12.2% SL. Posterior edge of maxillary plate straight. No longitudinal ridges on preopercular lobe. Otolith moderately elongate (OL:OH = 1.5–1.7).

Description. Counts and measurements are summarized in Tables 2–7. Snout bluntly pointed; interorbital space slightly convex. Posterior edge of maxillary straight with postero-dorsal and postero-ventral angles sharp and postero-ventral angle not extended; posterior rim of the maxillary vertical. Preopercular lobe with or without rudimentary longitudinal ridges; denticles of hind margin serration not extending into crests on preopercular lobe; inner edge of preopercle with 2–6 small denticles not extending along ventral branch. Two anal-fin spines. First anal fin pterygiophore slender, straight, pointed, but with narrow groove at anterior edge, reaching space between parapophyses of ninth and tenth abdominal vertebrae. First haemal spine with a narrow to moderate posterior expansion. Pelvic fin spine serrated along its outer edge; all other fin spines smooth.

Dentition. Premaxilla with a pair of canines near symphysis, followed posteriorly by a wide band of tiny conical teeth. Dentary with a pair of canines and a band of minute conical teeth near symphysis, followed posteriorly by a row of several small conical teeth and 2–3 enlarged canine-like teeth on each side. Vomer narrow V-shaped with few granular teeth anteriorly and 1–4 long teeth. Palatines narrow, with 1 row of granular teeth anteriorly and 1–2 rows posteriorly. Ectopterygoid narrow, with 1, rarely 2, rows of denticles. Tongue toothless.

Otolith morphology (n = 16). Otolith moderately slender, thin, up to about 6 mm length. OL:OH = 1.48–1.72; OL:OT about 7 to 8. Dorsal rim with broad, obtuse predorsal angle and distinct postdorsal angle very close to posterior rim. Ventral rim deepest slightly in front of its middle, below collum of sulcus. Rostrum well developed, moderately pointed; no or only weak excisura and antirostrum. Posterior rim blunt and nearly vertical. All rims smooth or slightly undulating. Inner face slightly convex with slightly supramedian-positioned sulcus. Sulcus shallow, with narrow, long, slightly deepened cauda and wide, shallow ostium. Ostium about twice as wide as cauda or less, with distinct colliculum. Cauda slightly widened posteriorly, with very slightly bent and rounded tip, terminating close to posterior tip of otolith. CaL:OsL = 1.25–1.35. Dorsal depression long, narrow. Ventral furrow distinct, close to ventral rim of otolith anteriorly and bending away from it backwards towards bent of cauda. Outer face slightly concave, rather smooth.

Size. Fishes reaching slightly over 90 mm SL.

Discussion. Parascombrops pellucidus is a small and gracile species which can be distinguished from most of its congeners except P. parvidens by the long pectoral fin (27.1–30.9% SL). For distinction from P. parvidens see above. Parascombrops pellucidus differs from P. philippinensis by the long pectoral fin, 27.1–30.9% SL (vs 21.5–27.2% SL), which reaches the anterior edge of the anal fin (vs not reaching the anterior edge of the anal fin), the higher number of gill rakers, 19–25 (vs 15–18), the slender tip of the first anal-fin pterygiophore (vs broad) and the rather long cauda of the otolith (CaL:OsL = 1.25–1.35 vs 1.05–1.25). After examinating representative material of P. pellucidus from the Bay of Bengal to the Gulf of Aqaba, (including specimens from the type-region), and the type specimens of P. adeni , we were unable to separate these two nominal species. There are possible subtle differences between the western and eastern Indian Ocean specimens in respect to the gill rakers ( Fig. 25 ). This difference, however, appears to be overlapping. On that basis we synonymise P. adeni into P. pellucidus , but are aware that we could be dealing with separate, cryptic species. Pairs of closely related species on the deep shelf in the western and eastern Indian Ocean have been recognized in other fishes, such as the macrourid Hymenocephalus (Schwarzhans 2014) and the ophidiid Spottobrotula ( Nielsen et al. 2014) . Molecular data might give further clarification, once more material becomes available.

Geographic and bathymetric distribution. Parascombrops pellucidus is widely distributed and common on the deep shelf from 179 to 210 m of the northern Indian Ocean from the Bay of Bengal, to the Red Sea and East Africa north of the equator in the West.

Figures

FIGURE 7 A – Q. Head profiles of Parascombrops, Caraibops, Kaperangus, Synagrops and Ƒerilus pseudomicrolepis. A, Parascombrops analis, MNHN 1998 - 1056, 82 mm SL; B, Parascombrops argyreus, ZMUC P 44272, 122 mm SL; C, Parascombrops glossodon n. sp., BMNH 1986.10. 9.79. 85, paratype, 4 mm SL; D, Parascombrops madagascariensis n. sp., MNHN 2008 - 1769, holotype, 68.5 mm SL; E, Parascombrops mochizukii n. sp., NMMBA-P 782, holotype, 166 mm SL; F, Parascombrops nakayamai n. sp., BSKU 102255, holotype, SL 97 mm; G, Parascombrops ohei n. sp., BSKU 72614, holotype, 75 mm SL; H, Parascombrops parvidens n. sp., BSKU 98886, holotype, 57.5 mm SL; I, Parascombrops pellucidus, USNM 44428, 64.5 mm SL; J, Parascombrops philippinensis, ZMA 112.453 (paralectotype of P. malyanus), 52 mm SL; K, Parascombrops serratospinosus, CAS 238016, 67.5 mm SL; L, Parascombrops spinosus, USNM 395230, 95.5 mm SL; M, Parascombrops yamanouei n. sp., NMMB-P 23097, paratype, 70 mm SL; N, Caraibops trispinosus, CAS 61040, 97.5 mm SL; O, Kaperangus microlepis, CAS 222834, 78.5 mm SL; P, Synagrops japonicus, ZMUC P 44324, 159 mm SL; 7 Q, Ƒerilus pseudomicrolpis, CAS 61164, 91 mm SL.

FIGURE 10 A – H. Dentition of vomer, palatines and ectopterygoids: A, Parascombrops pellucidus, USNM 392727, 84 mm SL; B, Parascombrops philippinensis, BMNH 2016.9. 14.1, paralectotype, 74 mm SL; C, Parascombrops serratospinosus, BSKU 16827, 67 mm SL; 10 D, Parascombrops spinosus, MNHN 1989 - 0411, 82 mm SL; E, Kaperangus microlepis, CAS 222834, 96.5 mm SL; F, Parascombrops yamanouei n. sp., NMMB-P 11343, paratype, 82 mm SL; G, Caraibops trispinosus, CAS 61040, 97.5 mm SL; H, Ƒerilus pseudomicrolepis, CAS 61164, 91 mm SL.

FIGURE 13 A – Q. Anal-fin pterygiophores and shape of large first anal-fin pterygiophore of genera Parascombrops, Caraibops, Kaperangus, Synagrops and of Ƒerilus pseudomicrolepis. A, Parascombrops analis, BSKU 94343, 74.5 mm SL; B, Parascombrops argyreus, AMS I. 42758 - 006, 120 mm SL; C, Parascombrops glossodon n. sp., USNM 436684, paratype, 73 mm SL; D, Parascombrops madagascariensis n. sp., MNHN 2008 - 1769, holotype, 68.5 mm SL; E, Parascombrops mochizukii n. sp., NMMBA-P 3887, paratype, 98 mm SL; F, Parascombrops nakayamai n. sp., BSKU 102255, holotype, 97 mm SL; G, Parascombrops ohei n. sp., BSKU 72614, holotype, 75 mm SL; H, Parascombrops parvidens n. sp., BSKU 15219, paratype, 70 mm SL; I, Parascombrops pellucidus, USNM 44428, 65.5 mm SL; J, Parascombrops philippinensis, BMNH 2016.9. 14.1, paralectotype, 64 mm SL; K, Parascombrops serratospinosus, CAS 238016, 67.5 mm SL; L, Parascombrops spinosus, MNHN 1989 - 0411, 82 mm SL; M, Parascombrops yamanouei n. sp., NMMB-P 15571, paratype, 102 mm SL; N, Caraibops trispinosus, CAS 61040, 97.5 mm SL; O, Kaperangus microlepis, CAS 222834, 78.5 mm SL; P, Synagrops japonicus, MNHN 1998 - 0993, 84 mm SL; Q, Ƒerilus pseudomicrolpis, CAS 61164, 91 mm SL.

FIGURE 15 A – AC. Otoliths (inner faces and representative ventral views): A – F, Parascombrops pellucidus (A – C = BMNH 1939.5.24.892 - 894, D – F = BMNH 1939.5.24.880 - 891); G – L, Parascombrops philippinensis (G – H = NSMT-P 59313, I = BSKU 116496, J = NSMT-P 57379, K – L = ZMA 112. 454, Synagrops malayanus paralectotype); M – O, Parascombrops spinosus (M – N = MCZ 169467, O = USNM 395230); P – R, Parascombrops serratospinosus (USNM 99324); S – U, Parascombrops yamanouei n. sp. (NMMB-P 23097); V – X, Caraibops trispinosus (15 V – W = USNM 407771, 15 X = USNM 407745); Y – AA, Kaperangus microlepis (CAS 222834); AB – AC, Ƒerilus pseudomicrolepis (USNM 407758).

FIGURE 25 A – B. Number of pseudobranchial filaments and gill rakers against specimen size in Parascombrops pellucidus, specifically for Eastern (type region of P. pellucidus) and Western Indian Ocean (type region of Synagrops adeni).