Cypselurus sp.

Shakhovskoy, Ilia B. & Parin, Nikolay V., 2022, A review of the flying fish genus Cypselurus (Beloniformes: Exocoetidae). Part 2. Revision of the subgenus Poecilocypselurus Bruun, 1935 with descriptions of three new species and five new subspecies and reinstatement of Exocoetus apus Valenciennes and E. neglectus Bleeker, Zootaxa 5117 (1), pp. 1-109 : 94-99

Cypselurus sp. ( poecilopterus ?)

Juveniles described below were previously identified as C. oligolepis . However, we reidentified them as probable juveniles of C. poecilopterus , having darker pigmentation of pectoral and pelvic fins with obscure (or even indiscernible) spots. One juvenile had one pectoral fin spotted and the opposite fin entirely dark. However, meristic and morphometric characters of these juveniles agree well with those of C. poecilopterus (see description of this species in Shakhovskoy & Parin 2010).

Synonymy and bibliography.

Cypselurus nigripennis (non Valenciennes).? Fowler, 1928: 84–85 (description of a juvenile; Shortland I. (Solomon Is.)).

Cypselurus oligolepis (non Bleeker).? Fedoryako 1982: 111 (juveniles listed as associated with drifting objects; Indian Ocean; in part: only fish from Station 4936).

Material examined. Forty-four specimens 23–77.5 mm SL.

Full morphological study. IORAS 04053 (7, 31– 53.5 mm SL), 13°37’N 86°53’E, 2- 3.02.1961 . IORAS 04054 (24, 35– 68.5 mm SL), 13°37’N 86°53’E, 2- 3.02.1961 . IORAS 04055 (1, 52.5 mm SL), 9°S 133°E, 18.07.1967 . IORAS 04056 (1, 77.5 mm SL), 8°18’N 120°25’E, 26.06.1971 . IORAS 04057 (1, 48 mm SL), 24°34’S 108°20’E, 27.07.1962 . IORAS 04058 (1, 64.5 mm SL), 8°18’N 120°25’E, 26.06.1971 . IORAS 04059 (1, 54.5 mm SL), ~ 3°47’S 144°45’E, 7.04.1966 . CAS 81855 (3, 50.5–58 mm SL), Apo Reef , South China Sea, 7.12.1949 .

Partial morphological study. IORAS 04053 (1, 28.5 mm SL), 13°37’N 86°53’E, 2- 3.02.1961 . IORAS 04060 (2, 41– 47 mm SL), 10°48’S 104°38’E, 2.03.1973 . IORAS 04061 (2, 23– 23.5 mm SL), 8°10’S 104°39’E, 22- 23.03.1961 .

Description. Meristic and morphometric characters are given in Tables 1–6 and 10. D 11–13, A 7–9 (usually 8), P I 14–16 (usually I 15), Spred 24–27 (usually 25–26), Str 8½–10 (usually 8½), Sp.br 21–26 (6–8 + 15–18), usually 22–25 (6–7 + 16–17), Vert 39–41 (24–26 + 14–17), usually 40–41 (26 + 14–15). Snout very short ( Fig. 37 ), lower jaw shorter than upper or of equal size; teeth small (not visible with the naked eye), conical (only largest specimen 77.5 mm SL has some teeth with additional cusps), arranged in 1–2 (very rarely three) rows. Palatine teeth always present, usually few in number.

Body deep and wide ( Fig. 37 ). Greatest body depth 3.95–5.0 in SL. Body width 1.01–1.24 and caudal peduncle depth 2.08–2.51 in greatest body depth. Head rather large and very deep ( Fig. 38a ), greatest head depth and head length 4.15–5.0 and 3.75–4.35 in SL, respectively. Head length 1.02–1.30 in dorso-caudal distance. Eyes large, eye diameter 7.45–10.9 in SL, 1.95-2.70 in head length, 1.0– 1.4 in interorbital width and 0.85–1.25 in postorbital distance; eye diameter decreasing strongly with growth.

Pectoral fins long, 1.4–1.65 in SL; their length increasing strongly with growth ( Fig. 38c ). Tip of pectoral fin reaching from middle to end of dorsal-fin base (rarely slightly beyond). First pectoral-fin ray unbranched, its length 2.35–2.9 in SL and 1.57–1.87 in lP. Pelvic-fin base closer to posterior edge of head than to origin of caudal-fin lower lobe (cV / pV = 0.69–0.88). Pelvic fin length 2.2–2.65 in SL and 1.44–1.69 in lP. Tip of pelvic fin reaching (nearly reaching) origin of caudal-fin lower lobe or slightly beyond.

Anal-fin origin far behind dorsal-fin origin, 1st anal-fin ray beneath 5 th –7 th dorsal-fin ray. Dorsal fin with 3–5 rays more than anal fin. Dorsal and anal fins very high, HD 5.15–6.35 and HA 7.55–10.4 in SL; height of both fins decreasing strongly with growth ( Fig. 38d–e ). Longest ray in dorsal fin—4 th –8 th (occasionally 2 nd or 3 rd), in anal fin—2 nd or 3 rd. Tip of last dorsal-fin ray protruding well beyond origin of caudal-fin upper lobe (only in the largest fish 77.5 mm SL slightly not reaching it). Middle and posterior dorsal-fin rays elongated, tip of penultimate ray (rays) protruding beyond tip of last ray (occasionally at the same level or slightly ahead).

Pigmentation. Body pale brown to dark brown ( Fig. 37 ), ventral side usually darker than dorsal one. Body bands usually absent, but some juveniles with 1–4 dark bands: above bases of pectoral and pelvic fins, between them, above anus and (or) above posterior part of anal-fin base. Lower surface of head brown to dark brown, usually with paler chin, “lips” and distal parts of branchiostegal rays; in a few fish pale with aggregations of melanophores under eyes (on bases of branchiostegal rays) and on chin.

Pectoral fin pigmentation highly variable ( Fig. 39 ): brown to dark brown usually with a transverse row of 2–11 large pale spots proximally (occasionally absent), pale fin tip and two small pale areas near tips of 2 nd and 3 rd rays; distal part of pectoral fin usually with rows of darker and paler spots, which in some fish quite evident ( Fig. 39a–b ), in others visible only under back lighting ( Fig. 39d–f ) and in still others (fish with darkest pigmentation) not visible at all ( Fig. 39c ).

Like pectoral fins, pelvic fins pigmentation also variable: from entirely brown or dark brown ( Fig. 40a ), sometimes with a row of faint pale spots basally, to vaguely spotted ( Fig. 40e–f ) and obviously spotted ( Fig. 40b–d ).

Dorsal fin more or less uniformly pigmented, dark gray to dark brown. Anal fin in juveniles 23–35 mm SL entirely brown to dark brown posteriorly and pale with pigmentation only along the fin base anteriorly. In juveniles 35–77.5 mm SL, anal fin brown to dark brown (sometimes paler basally) with pale anterior corner (between 2–4 anterior rays distally).

Caudal fin ( Fig. 37 ) pale with pale brown to dark brown base, dense brown melanophores along lower lobe rays (except uppermost rays) and sparse ones on upper lobe (occasionally absent). In fish 60–77.5 mm SL, caudal fin usually with 1–2 dark bands on lower lobe ( Fig. 37f ) and, sometimes, also with one band on upper lobe distally.

Coloration in life. No data.

Intraspecific variation. The juveniles may be sorted into three morphs: a pale morph (paired fins paler and distinctly spotted), a dark morph (paired fins uniformly dark and not spotted, but pectoral fins sometimes, like in C. oligolepis , with a transverse row of paler spots proximally), and an intermediate morph (paired fins dark, but vague spottiness discernible if fins viewed against the light). An intermediate morph juvenile has one pectoral fin spotted and the opposite fin entirely dark. The pale morph is clearly identifiable as C. poecilopterus . The dark morph is very similar to C. oligolepis and C. neglectus and may be misidentified as one of these species. But the intermediate morph, binding these two morph into a whole, suggests that all three morphs belong to a single species— C. poecilopterus . The variation in pigmentation intensity may be a result of intraspecific polymorphism or different physiological conditions of fish at the time of capture and fixation. This matter needs further research.

Comparative remarks. The juveniles of this species, and especially the dark morph, may be confused with juveniles of C. oligolepis and C. neglectus . However, they differ in higher dorsal and anal fins (HD> 15.5 vs. usually <15.5% SL, HA usually> 10.5 vs. usually <10.5% SL, see Fig. 38d–e ), deeper and wider body and head (H and HC> 20 vs. usually <20% SL, h> 8.5 vs. usually <8.5% SL ( Fig. 38a–b ), p usually> 18 vs. usually <18% SL, io usually> 12.5 vs. usually <12.5% SL), larger eyes and shorter snout (ao usually <3 vs. usually> 3, index o/ao usually> 3.5 vs. usually <3.5, see Fig. 38f ), longer pectoral fins (lP usually> 62 vs. usually <62% SL (see Fig. 38c ), lP 1 usually> 35 vs. usually <35% SL, index lP/lV usually> 1.5 vs. usually <1.5). Also, they differ from C. oligolepis and C. neglectus neglectus in elongated middle and posterior dorsal-fin rays (penultimate ray tip reaching further back than last ray tip).

Distribution. The juveniles described above were collected in the Bay of Bengal, off Christmas Island (Indian Ocean), off western Australia, in the Arafura Sea, off Cape York, in the Sulu Sea and near Apo Reef; thus, within the range of C. poecilopterus (see Shakhovskoy 2018).

Figures

FIGURE 37. Cypselurus sp. (poecilopterus?): (A)—31 mm SL, IORAS 04053, 13°37’N 86°53’E; (B)—37 mm SL, IORAS 04054, same place; (C)—48 mm SL, IORAS 04057, 24°34’S 108°20’E; (D)—54.5 mm SL, IORAS 04059, ~3°47’S 144°45’E; (E)—64.5 mm SL, IORAS 04058, 8°18’N 120°25’E; (F)—77.5 mm SL, IORAS 04056, 8°18’N 120°25’E.

FIGURE 38. Size variation of morphometric characters (in % SL) in Cypselurus sp. (poecilopterus?) (+), C. oligolepis (□), C. clariangulatus (♦), C. izumii (x), C. neglectus (○), C. starksi (◊) and C. nossibe (▲): (A)—least depth of caudal peduncle (h); (B)—greatest head depth (Hc); (C)—pectoral fin length (lP); (D)—dorsal fin height (HD); (E)—anal fin height (HA); (F)—eye length divided by snout length (index o/ao).

FIGURE 39. Pectoral fins of Cypselurus sp. (poecilopterus?): (A)—43 mm SL, IORAS 04054, 13°37’N 86°53’E; (B)—51 mm SL, IORAS 04054, same place; (C)—53 mm SL, IORAS 04053, 13°37’N 86°53’E; (D)—54 mm SL, IORAS 04054, 13°37’N 86°53’E; (E)—64.5 mm SL, IORAS 04058, 8°18’N 120°25’E; (F)—77.5 mm SL, IORAS 04056, 8°18’N 120°25’E.

FIGURE 40. Pelvic fins of Cypselurus sp. (poecilopterus?): (A)—37 mm SL, IORAS 04054, 13°37’N 86°53’E; (B)—48 mm SL, IORAS 04054, same place; (C)—54.5 mm SL, IORAS 04059, ~3°47’S 144°45’E; (D)—64 mm SL, IORAS 04054, 13°37’N 86°53’E; (E)—64.5 mm SL, IORAS 04058, 8°18’N 120°25’E; (F)—77.5 mm SL, IORAS 04056, 8°18’N 120°25’E.