Cypselurus oligolepis apus ( Valenciennes, 1847 )

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 : 38-45

Cypselurus oligolepis apus ( Valenciennes, 1847)

Synonymy and bibliography.

Exocoetus apus Valenciennes in Cuvier & Valenciennes, 1847: 107–108 (original description; near Macao, China). Bruun 1937: 183 (description of type). Collette et al. 1997: 10 (description of type; synonym of C. oligolepis ).

Exocoetus brachysoma Bleeker, 1865: 107 , 111–112 (original description; Indonesia; in part?). Günther 1866: 295–296 (description; Indo-Pacific; in part). Bleeker 1866 –1872: 68, 70–71, Tab. CCXLVII, Pl. Scombres I, fig. 3 (description; Indonesia; in part?). Weber 1913: 125 (Laiwui, Obi major). Weber & de Beaufort 1922: 189–190 (synonym of C. oligolepis ). Parin 1960a: 254 (listed as synonym of C. oligolepis ).

Exocoetus nigripennis (non Valenciennes). Bleeker 1865: 108, 120–121 (description; Amboina (Ambon), New Guinea; in part). Bleeker 1866 –1872: 67, 70 (description; Amboina (Ambon), New Guinea; in part).

Cypselurus oligolepis .? Seale 1906: 15 (listed; Shortland I.).? Seale 1935: 348 (short description; Bellona I.).? Munro 1958: 137 (New Guinea; listed). Parin 1960a: 222, 254, 255, 279 (description (after Weber & de Beaufort 1922 and Woods & Schultz 1953); western Pacific; in part). Munro 1967: 117, 121, Pl. 13 fig. 193 (New Guinea; short description; in part).? Gillett & Ianelli 1991: 3 (listed; New Guinea).? Belyanina 1993: 118–120, fig. 4 (early life history stages; Eastern Australia (Lizard I.); in part?).

Cypsilurus oligolepis .? Jordan & Seale 1906: 211 (listed; Shortland I., Solomon Is.). Weber & de Beaufort 1922: 180, 189–190 (description; Indo-Australian Archipelago; in part).

Material examined. Sixty-nine specimens 20–155 mm SL

Philippines. Full morphological study. ZMUC uncat (2, 127– 131 mm SL), 9°36’N 125°46’E, 30- 31.07.1951 .

Partial morphological study. USNM 135803 * # (5, 119– 139.5 mm SL), Catbalogan, Samar I., 15.04.1908 . USNM 135805 * # (2, 125.5– 128 mm SL), Catanduanes I., Agoho Pt., 10.06.1909 . USNM 135806 * # (1, 129 mm SL), San Miguel Bay, Luzon I., 5.07.1909 . ZMH 12773* (1, 120.5 mm SL), Cebu I., 16.06.1913 .

Indonesia. Full morphological study. SOSC Acc. No. 56 (1, 94.5 mm SL), 1°53’N 127°39’E, 25.09.1963. SOSC uncat (2, 85– 92 mm SL), 1°53’N 127°39’E, 25.09.1963. SOSC uncat (1, 92.5 mm SL), 1°00’N 127°56’E, 21.09.1978. SOSC uncat (5, 116.5– 145 mm SL), 1°20’N 128°01–06’E, 24- 25.09.1963. ZIN 4781 * (1, 137 mm SL), Amboina, 1858 .

Partial morphological study. CAS 129104 ( SU 29104 )* (4, adults), Maluku Prov., Ternate, 11.06.1929 . RMNH 9950 * (1, 148 mm SL), Laiwui , Obi, 27.07.1917 . SIO 73-178 * (1, 142 mm SL), 1°31’S 130°34’E, 17.12.1972 . USNM prereg. No. 5210* (1, 137 mm SL), ~ Indonesia – Oceania .

Melanesia. Full morphological study. IORAS 04005 (1, 113 mm SL), Rabaul, 11- 12.05.1971 . IORAS 04006 (8, 110– 144 mm SL), Rabaul, 11- 12.05.1971 . AMS uncat. (1, 127.5 mm SL), Kimbe, 4.11.1971 . ZMUC uncat. (8, 113– 131 mm SL), 4°25’S 160°00’E, 6- 7.10.1951 .

Partial morphological study. CSIRO C.1481* (1, 122 mm SL), Möwe Harbour , New Britain, 2.01.1949 . USNM 312909 * # (1, 124.5 mm SL), 1°39’S 150°38’E, 21.01.1990 . USNM 312910 * (1, 118 mm SL), Fullerborn Harbour, New Britain, 20.02.1990 . USNM 312911 * (2, 119 mm SL), Matupit Bay, Simpson Hr., Rabaul, 23.02.1990 .

New Guinea. Full morphological study. AMS uncat. (1, 32 mm SL), Sek Harbour, 21.09.1971 . AMS uncat. (1, 42 mm SL), Madang, 12.08.1971 . CAS 128237 ( SU 28237 ) (3, 38– 43 mm SL), Madang, 6.05.1929 . SOSC uncat (1, 39 mm SL), 08°03’S 148°07’E, 17.06.1979 . SOSC uncat (1, 41 mm SL), 00°51S 135°35’E, 30.06.1979 .

Partial morphological study. AMS IB.1439* (1, 136 mm SL), off Japen Is., Schouten Is , NE of Geelvink Bay . AMS IB.1440* (1, 135 mm SL), off Japen I. (Schouten Is.), NE of Geelvink Bay . AMS uncat. (3, 20– 34 mm SL), Sek Harbour, 21.09.1971 . USNM 294789 * (2, 80– 90 mm SL), Trobriand Is., Off NW corner of Kiriwina I., 8- 9.06.1970 .

Type material. BMNH 1866.5.2.33* (1, 155 mm SL), no data. MNHN B834* (1, 122 mm SL), Macao ( China). RMNH 6972* (2, 102– 140 mm SL), no data.

Exocoetus apus is a senior synonym of C. oligolepis , but as the name has not been used as valid since the original description while C. oligolepis was widely used ( Collette et al. 1997), the former should be regarded as nomen oblitum and the latter as nomen protectum. However, splitting Cypselurus oligolepis into several subspecies permit us to use apus as valid name for a subspecies.

Types. Type of Exocoetus apus ( Fig. 15 ) and syntypes of Exocoetus brachysoma Bleeker were examined by the second author. Their characters are given below.

MNHN B834 , Macao (Chine), Eydox et Souleyet. Length 122 mm SL. D 11, A 9, P I 14, Spred 24, Str 7½, Sp.br 23 (7 + 16), Vert 39 (24 + 15). Measurements (in % SL): aA 78.6, aD 67.2, aV 55.7, cV 1 32.3, pV 42.7, c 25.3, o 8.9, ao 1 6.3, io 1 10.0, H ~20.7, h 7.9, Dc 28.7, lP 59.8+, lP 1 38.9, lV 29.3, p 15.2. Pectoral fins black to 10 th ray with pale tip. Pelvic fins pale (one of the fins with dark pigmentation near outer margin distally), their tip reaching middle of anal-fin base. First anal-fin ray beneath 6 th dorsal-fin ray. Jaw teeth numerous, tricuspid, arranged in many rows. Palatine teeth present. Description of the type of E. apus by Bruun (1937) differs somewhat from our one in: aV 58.4, lP 66.0, and palatine teeth absent .

Syntype of E. brachysoma ( BMNH 1866.5.2.33, no label data). Length 155 mm SL (female). D 104, A 8, P I 15, Spred 27, Str 9, Sp.br 18 (3 + 15), Vert 41 (26 + 15). Measurements (in % SL): aA 80.8, aD 72.7, aV 58.0, cV 1 34.5, pV 41.1, c 25.0, o 8.3, ao 1 6.7, io 1 8.2, H 22.1, Dc 25.7, lP 63.0, lV 29.6, lD 17.1, lA 9.8, HD -, HA -. Pectoral fins gray to 9 th ray with pale tip. First anal-fin ray beneath 4 th dorsal-fin ray. Lower jaw shorter than upper jaw. Jaw teeth with additional cusps (but true tricuspid teeth absent). Palatine teeth present.

Two presumed syntypes of E. brachysoma ( RMNH 6972, no label data) probably belong to C. o. apus ; however, we are not entirely certain, as the larger specimen (140 mm SL) might be C. neglectus and the smaller (102 mm SL) C. oligolepis oligolepis .

Length 140 mm SL. D 12, A 8, P I 13, Spred 25, Str 8, Sp.br 22 (5 + 17). Measurements (in % SL): cV 1 34.6, pV 40.7, c 24.4, o 9.2, io 1 8.9, H 18.8, h 7.9, Dc 28.7, lP -, lV -, p 14.0. Pigmentation vanished. First anal-fin ray beneath 6 th dorsal-fin ray. Jaw teeth pulled out. Palatine teeth present, arranged in 3 rows.

Length 102 mm SL. D 12, A 8, P I 13, Spred 26, Str 8½. Measurements (in % SL): cV 1 33.7, pV 42.7, c 23.8, o 9.2, io 1 8.3, H 17.9, Dc 25.9, lP -, lV -, p 14.1. First anal-fin ray beneath 6 th dorsal-fin ray.

4 Specimen might have 11 rays as there are signs of one ray having been torn away in the x-ray and there are 11 interneural bones.

Description. Meristic and morphometric characters are given in Tables 1–5 , 8 and 10. D 11–13 (usually 12–13), A 7–9 (usually 8–9), P I 12–15 (usually I 14), Spred 21–28 (usually 23–26), Str 6½–8½ (usually 8–8½), Sp.br 20–26 (4–8 + 15–19), usually 21–24 (5–7 + 16–18), Vert 38–41 (24–26 + 13–16), usually 40 (25–26 + 14–15). Snout short ( Fig. 16 ), jaws usually of equal size or upper jaw longer, but 17% of fish with lower jaw longer. Jaw teeth small to medium-sized (not visible or barely visible to the naked eye), tricuspid, conical and with additional cusps. In larger fish teeth with additional cusps and tricuspid teeth prevailing, and in smaller fish conical teeth prevailing. Juveniles <85 mm SL with conical teeth only. Teeth arranged in 2–4 rows, in juveniles <50 mm SL in 1–2 rows. Palatine teeth always present, usually numerous.

Body rather deep. Greatest body depth changing slightly with growth: in juveniles 30–95 mm SL it fits 4.5–5.4 in SL, in fish 110–150 mm SL 4.3–5.1 in SL. Body width 1.05–1.5 and caudal peduncle depth 2.1–2.9 in greatest body depth. Greatest head depth and head length hardly changing with growth, 4.85–5.80 and 3.5–4.2 in SL, respectively. Head length 0.92–1.21 in dorso-caudal distance. Eyes very large, eye diameter decreasing markedly with growth ( Fig. 6a ): in juveniles 30–95 mm SL eye diameter 8.7–9.9 in SL, 2.1–2.8 in head length, 0.97–1.16 in interorbital width and 0.85–1.16 in postorbital distance ( Fig. 6e ); in fish 110–150 mm SL 9.3–12.3 in SL, 2.58–3.06 in с, 0.97–1.19 in io and 1.03–1.28 in po.

Pectoral fins relatively long, their length increasing with growth up to about 100 mm SL, and afterwards nearly constant ( Fig. 6c ): in juveniles 30–95 mm SL pectoral fin 1.55–1.85 in SL and in fish 110–150 mm SL, 1.48–1.65 in SL. Tip of pectoral fin reaching the posterior half of dorsal-fin base or slightly beyond, never protruding past middle of caudal peduncle; in juveniles under 45 mm SL to about middle of dorsal-fin base. First pectoral-fin ray unbranched, its length hardly increasing with growth, 2.43–2.94 in SL and 1.56–1.87 in lP. Pelvic-fin base much closer to posterior edge of head than to origin of caudal-fin lower lobe (cV / pV = 0.67–0.85); pelvic fins not changing position as fish grows. Pelvic-fin length decreasing strongly from juveniles to adults ( Fig. 6d ): in juveniles 30–95 mm SL pelvic fin 2.3–3.5 in SL and 1.29–2.13 in lP ( Fig. 6f ); in fish 110–150 mm SL, 3.2–3.9 in SL and 2.02–2.44 in lP. Tip of pelvic fin in small juveniles <45 mm SL reaching origin of caudal-fin lower lobe or protruding beyond; in juveniles 80–120 mm SL reaching from end of anal-fin base (sometimes not quite reaching) to middle of caudal peduncle; in fish 115–145 mm SL reaching from middle to end of anal-fin base, never protruding beyond it.

Anal-fin origin far behind dorsal-fin origin (1st anal-fin ray beneath 4 th –7 th dorsal-fin ray, usually beneath 5th– 6 th ray). Dorsal fin with 2–5 rays more than anal fin. Height of dorsal and, especially, anal fins decreasing markedly with growth. In juveniles 30–95 mm SL, HD 6.6–8.0 and HA 8.5–11.9 in SL; in fish 110–150 mm SL, HD 7.6–10.1 and HA 11.35–14.9 in SL. Longest ray in dorsal and anal fins—2 nd or 3 rd. Tip of last dorsal-fin ray reaching from middle of caudal peduncle to the origin of caudal-fin upper lobe (rarely slightly beyond in juveniles <45 mm SL). Middle and posterior rays of dorsal fin not elongate, penultimate rays not protruding beyond tip of last ray (slightly beyond in some juveniles <45 mm SL).

Pigmentation. Body of juveniles ( Fig. 16a–b ) pale brown to dark brown, ventral side usually darker than dorsal. Body bands absent (except a juvenile 34 mm SL with a faint dark band between pectoral and pelvic fins).

The head usually darker than body, its lower surface in juveniles 30–80 mm SL brown with chin and distal parts of branchiostegal rays paler, or in some fish rather pale with pigmentation mainly under the eye. Later the pigment on the lower surface of head begins to disappear, and in fish> 110 mm SL lower surface of head pale, sometimes with few dots near the lower jaw symphysis and under the eye. Adults with a few small dark specks on gill covers and under eyes.

Pectoral fins in juveniles 20–45 mm SL brown or dark brown with pale ray tips (especially conspicuous in rays 1 st –3 rd); pale transverse band or a row of spots always absent ( Fig. 17a ). In fish> 80 mm SL pectoral fin pale brown to dark brown to 7 th –9 th (to 10 th in the holotype) ray distally (to 6 th –8 th ray proximally, sometimes a small flat “mirror” present), with a broad pale tip and, sometimes, with a very narrow pale posterior edging ( Fig. 17b–c ).

Pelvic fins in juveniles 20–90 mm SL ( Fig. 17d–e ) entirely brown or dark brown (sometimes slightly paler proximally). In fish 85–95 mm SL pelvic fins pale with vestigial pigmentation as faint dots or streaks along some rays. In fish ≥ 95 mm SL, pelvic fins pale ( Fig. 17f ).

Dorsal fin in juveniles 20–45 mm SL sparsely covered with melanophores (more densely in upper and posterior parts). In fish 85–95 mm SL dorsal fin gray or pale brown, sometimes with blackish upper margin. In fish ≥ 110 mm SL, dorsal fin gray, usually with pale brownish or yellowish tinge basally.

Anal fin in a 20 mm SL juvenile pale with few brown dots near fin base. In juveniles 30–80 mm SL, anal fin pale with brown dots near fin base anteriorly and in the posterior part distally (usually aggregated in a brown spot between 4–5 posterior rays). In fish ≥ 85 mm SL anal fin pale.

Caudal fin in fish 20–45 mm SL pale with pale brown base and brown pigmentation between lower lobe rays (except uppermost ones); dark bands absent ( Fig. 16a–b ). In fish ≥ 85 mm SL, caudal fin pale brown or brown, usually with darker upper lobe and fork distally ( Fig. 16c–e ). Some fish from Melanesia also with darker caudal-fin base.

Coloration in life. No data.

Maximum size. The maximum length of C. o. apus in our material was 155 mm SL (syntype of E. brachysoma, BMNH 1866.5.2.33). The largest female and male were 144 and 131 mm SL, respectively.

Common names. The name “chunky largescale flying fish” (Russian: “короткотелый малочеШуйный стрижехвост”) is proposed here for the subspecies C. o. apus .

Comparative remarks. Cypselurus o. apus differs from C. o. oligolepis and C. o. persicus in shorter pelvic fins (in adults usually <30% SL vs. usually> 30% SL, see Fig. 6c, f ), fewer vertebrae and fewer rays in dorsal and anal fins (see Tables 1–5 ); it also differs from C. o. oligolepis in the pigmentation of pectoral and pelvic fins in juveniles, from C. o. persicus in shorter pectoral fins (usually <66% SL vs.> 66% SL, see Fig. 6c ) and fewer predorsal and transverse scales ( Tables 2–3). From C. o. georgii in larger eye ( Fig. 6a ) and smaller postorbital distance (index po/o in adults 1.03–1.28 vs. 1.36–1.61, see Fig. 6e ), deeper body and head of adults (H usually> 20 vs. usually <20% SL, Hc usually> 19 vs. usually <19% SL), fewer pectoral-fin rays (usually ≤ 15 vs. usually 16), and in the pigmentation of head and pectoral, pelvic and caudal fins in juveniles.

Cypselurus o. apus probably can hybridize with C. neglectus (see below for description of C. neglectus ). Thus, we were not able to ascribe a specimen (ZMUC uncat. 4°25’S 160°00’E, 6–7 October 1951) to either of these taxa with certainty. The specimen has a deep body and short pelvic fins like C.o. apus , but the pelvic-fin origin is shifted posteriorly as in C. neglectus . Its characters are: 143 mm SL (mature female), D 12, A 8, P I14, Spred 25, Str 8½, Sp.br 20? (5? + 15). Measurements (in % SL): aA 79.7, aD 71.3, aV 59.4, cV 34.1, pV 37.6, c 25.2, po 10.5, o 8.6, ao 4.8, io 10.4, Hc 19.5, H 22.3, h 7.8, Dc 27.2, lP 64.2, lP 1 40.6, lV 28.6, lD 19.5, lA 9.8, HD 11.2, HA 7.3, p 15.3. Pectoral fins dark brown to 8 th ray with pale tip. One of pectoral fins is devoid of pigmentation in its proximal half. Pelvic fins pale. Dorsal fin gray, anal fin pale. Caudal fin pale brown, its base dark brown. Lower jaw slightly longer than upper jaw. Jaw teeth numerous, mainly conical, some with additional cusps and only a few tricuspid; arranged in 3–4 rows. Palatine teeth present, numerous. The 3 rd dorsal-fin ray and 2 nd anal-fin ray longest. First anal-fin ray beneath 7 th dorsal-fin ray. Tip of last dorsal-fin ray nearly reaching origin of caudal-fin upper lobe.

This presumed hybrid, capable of reaching sexual maturity, might indicate that subspecies of C. oligolepis and C. neglectus are (or have formerly been) components of a single, highly polymorphic species. However, this should be a matter of further research. Interspecific and even intergeneric natural hybrids are common in different fish groups (e.g. sturgeons, cichlids, chaetodontids, and many others), and in some cases reach maturity (e.g. Oxyporhamphus convexus x O. micropterus , see Parin et al. 1980: 153).

Intrasubspecies variation. There are minor variations in frequencies of some counts and in values of some measurements between specimens of Cypselurus o. apus from different regions (see Tables 1–5 , 8, 10 ). For example, fish from Melanesia have fewer dorsal-fin rays and Indonesian fish have fewer vertebrae and transverse scales. Fish from Melanesia have, on average, a larger eye and longer head, and fish from Indonesia a shallower head (in adults) and a shorter postventral distance. However, we consider these differences to have no taxonomical significance.

Biology. Males mature at 120 mm SL, females at 128 mm SL. Close to mature or mature fishes were captured at Rabaul, Papua New Guinea, in May ( IORAS 04006 ), at Samar I. in April ( USNM 135803 ), near Halmahera I. in September ( SOSC uncat.). Small juveniles 20–34 mm SL were captured at Sek Harbour in September ( AMS uncat.), juveniles 38–43 mm SL were captured at Madang in May ( CAS 128237 ) and August ( AMS uncat.), and juveniles 39–41 mm SL were captured in June at 08°03’S 148°07’E and 00°51S 135°35’E (both SOSC uncat.). These data suggest C. o. apus spawns at least from April to September .

Distribution. Cypselurus o. apus is distributed ( Fig. 18 ) in neritic waters from Macao, China (MNHN B834, type of E. apus ) through eastern Philippines, Moluccas, northern New Guinea to Melanesia with the easternmost occurrence at 4°25’S 160°00’E (ZMUC uncat.). Belyanina (1993) reported presumably this subspecies from Lizard I., Eastern Australia.

Cypselurus o. apus has a nearly allopatric distribution with C. o. oligolepis , and the border between their ranges coincides roughly with Wallace’s Line—the border for many sibling taxa of marine inshore fishes and invertebrates (e.g. Fleminger 1986, Woodland 1986).

Figures

FIGURE 6. Size variation of morphometric characters (in % SL) in Cypselurus oligolepis (□— C. o. oligolepis, ○— C. o. apus, ∆— C. o. persicus, +—C. o. georgii), C. clariangulatus (◊) and C. izumii (x): (A)—diameter of eye (o); (B)—width of interorbital space (io); (C)—length of pectoral fin (lP); (D)—length of pelvic fin (lV); (E)—postorbital distance divided by diameter of eye (index po/o); (F)—pectoral fin length divided by pelvic fin length (index lP/lV).

FIGURE 15. Type of Exocoetus apus (122 mm SL, MNHN B834, Macao): (A)—side view; (B)—view from above. Photos provided by Jonathan Pfliger and Zouhaira Gabsi (MNHN).

FIGURE 16. Cypselurus oligolepis apus: (A)—32 mm SL, AMS uncat., Sek Harbour; (B)—41 mm SL, SOSC uncat., 00°51’S 135°35’E; (C)—94.5 mm SL, SOSC uncat., 01°53’N 127°39’E; (D)—116.5 mm SL, SOSC uncat., 01°20’N 128°01’E; (E)— 134 mm SL, IORAS 04006, Rabaul.

FIGURE 17. Pectoral (A–C) and pelvic (D–F) fins in Cypselurus oligolepis apus: (A)—41 mm SL, SOSC uncat., 00°51’S 135°35’E; (B)—92.5 mm SL, SOSC uncat., 1°00’N 127°56’E; (C)—144 mm SL, IORAS 04006, Rabaul; (D)—32 mm SL, AMS uncat., Sek Harbour; (E)—43 mm SL, CAS 128237 (SU 28237), Madang; (F)—110 mm SL, IORAS 04006, Rabaul.

FIGURE 18. Distribution of Cypselurus oligolepis apus (○) and C. clariangulatus (◊). Filled symbols indicate capture loca- tion for fish ≤ 100 mm SL, open symbols indicate capture location for fish> 100 mm SL. Positions of holotypes marked with asterisk.