Cypselurus izumii, Shakhovskoy & Parin, 2022

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 : 45-47

Cypselurus izumii sp. nov.

Synonymy and bibliography. No data.

Material examined. Twelve specimens 156.5–188 mm SL.

Full morphological study. IORAS 03994 (8, 156.5– 187 mm SL), 20°01’S 115°00’E, 12.01.1988 . IORAS 03995 (holotype) (1, 187 mm SL), 20°01’S 115°00’E, 12.01.1988 . IORAS 03996 (paratype) (1, 188 mm SL), 20°01’S 115°00’E, 12.01.1988 . IORAS 03997 (ex FRSKU 112220 ) (paratype) (1, 174 mm SL), 26°27’S 112°44’E, 8.01.1988 . IORAS 03998 (ex FRSKU 112303 ) (paratype), (1, 171 mm SL), 24°00’S 112°45’E, 16.12.1987 .

Holotype ( Fig. 19a ). IORAS 03995 , R / V Shoyo Maru Sta. 16, 20°01’S 115°00’E, 12 January 1988, water temperature 27°С. Length 187 mm SL (female). D 12, A 9, P I 15, Spred 25, Str 8½?, Sp.br 23 (6 + 17), Vert 43 (27 + 16). Measurements (in % SL): aA 80.7, aD 69.2, aV 56.7, cV 35.9, pV 41.7, c 22.3, po 10.1, o 6.8, ao 4.8, io 10.1, Hc 18.0, H 18.7?, h 7.9, Dc 27.7, lP 70.9, lP 1 41.4, lV 37.1, lD 18.8, lA 10.2, HD -, HA 7.5 , p 13.8. Body dark dorsally, silvery ventrally. Pectoral fins brown to 9 th ray with pale tip. Tip of pectoral fin reaching middle of caudal peduncle. Pelvic fins pale, their tip protrudes beyond end of anal-fin base. Dorsal fin gray, tip of its last ray slightly protruding beyond middle of caudal peduncle. Anal fin pale, its first ray beneath 6 th dorsal-fin ray. The 2 nd anal-fin ray longest. Caudal fin pale brown, slightly darker near fork. Lower and upper jaws about equal. Jaw teeth are rather large (clearly visible with the naked eye), numerous, tricuspid (a few conical teeth also present), and arranged in 3 rows. Palatine teeth numerous.

Paratypes. IORAS 03996 , 188 mm SL , R / V Shoyo Maru Sta. 16, 20°01’S 115°00’E, 12 January 1988 . IORAS 03997 (ex FRSKU 112220 ), 174 mm SL , R / V Shoyo Maru, 26°27’S 112°44’E, 8 January 1988 . IORAS 03998 (ex FRSKU 112303 ), 171 mm SL , R / V Shoyo Maru, 24°00’S 112°45’E, 16 December 1987 .

Description. Meristic and morphometric characters are given in Tables 1–6 and 10. D 11–14 (usually 12–13), A 8–10, P I 14–16, Spred 25–30 (usually 25–28), Str 8½–10 (usually 8½), Sp.br 22–24 (6–7 + 16–17), Vert 42–44 (26–28 + 15–16). Snout short and deep, upper jaw rounded at tip. Lower jaw usually shorter than upper or of equal size, rarely slightly longer. Jaw teeth numerous, rather large (usually clearly visible with the naked eye) and tricuspid, some fish also with few conical teeth; arranged in 3–4 rows. Palatine teeth always present, numerous.

In fish 155–190 mm SL, body from elongate to quite deep; greatest body depth 4.5–5.45 in SL. Body width 1.31–1.56 in SL and depth of caudal peduncle 2.35–2.73 in SL. Greatest head depth 5.3–5.65 in SL. Head length 4.1–4.5 in SL and 1.06–1.30 in dorso-caudal distance. Eyes relatively small ( Fig. 6a ), eye diameter 12.8–14.7 in SL, 3.1–3.3 in с, 1.2–1.5 in io and 1.29–1.48 in po ( Fig. 6e ).

Pectoral fins very long ( Fig. 6c ), their length 1.4–1.5 in SL. Tip of pectoral fin always protruding beyond end of dorsal-fin base, usually reaching middle of caudal peduncle or slightly further. First pectoral-fin ray unbranched, its length 2.25–2.5 in SL and 1.6–1.7 in lP. Pelvic-fin origin closer to posterior margin of head than to origin of caudal-fin lower lobe (cV/pV = 0.72–0.87). Pelvic fins extremely large ( Fig. 6d ), their length 2.7–3.05 in SL and 1.91–2.05 in lP ( Fig. 6f ). Tip of pelvic fin usually protruding beyond end of anal-fin base (occasionally reaching only penultimate or last anal-fin ray).

Anal-fin origin far behind dorsal-fin origin (1 st anal-fin ray beneath 6 th –7 th dorsal-fin ray). Dorsal fin with 2–5 rays more than anal fin. Height of dorsal and anal fins 7.75–9.4 and 11.75–13.7 in SL, respectively. The 2 nd ray in dorsal and anal fins longest. Tip of last dorsal-fin ray reaching middle of caudal peduncle or further, but never reaching origin of caudal-fin upper lobe. Middle and posterior rays of dorsal fin not elongated (tips of penultimate rays not extending beyond tip of last ray).

Pigmentation. Body of fish 155–190 mm SL with typical flying fish “pelagic” pigmentation. Dark specks on gill covers and under eyes absent or very sparse. Pectoral fins ( Fig. 19b ) pale brown to dark brown (sometimes with violet tinge) to 9 th –10 th (rarely to 8 th) ray, with very small, flat “mirror” in some fish. Proximal part of pectoral fin sometimes slightly paler than distal one. Pectoral fins always with clear-cut broad pale tip, posterior pale edging usually absent. Pelvic fins pale, but occasionally with vestigial pigmentation distally. Dorsal fin gray or, rarely, pale brown. Anal fin pale. Caudal fin pale brown, tip of upper lobe and fork margin usually slightly darker.

Coloration in life. No data.

Maximum size. The largest specimen of C. izumii in our material was 188 mm SL ( IORAS 03996 , paratype) .

Intraspecific variation. No data.

Comparative remarks. Cypselurus izumii differs from C. oligolepis (and from all species of the genus Cypselurus ) in considerably longer pelvic fins in fish> 155 mm SL (lV usually> 33 vs. usually <33% SL) and in lower value of index lP/lV ( Fig. 6d, f ); it also differs from all subspecies of C. oligolepis , except C. o. persicus, in higher number of vertebrae (42–44 vs. 38–43, usually 40–42). Besides pelvic-fin length, C. izumi differs from C. poecilopterus , C. simus and C. callopterus in absence of spots on pectoral fins. Cypselurus izumii is very similar to C. starksi , but differs from this species in longer pelvic fins (see above), lower index lP/lV (1.91–2.05 vs. 2.07–2.21), higher dorsal fin (10.6–12.9 vs. 9.4–11.6% SL), fewer Str (usually 8½–9 vs. usually 9–9½), and in pectoral fin pigmentation (pigmented to (8 th)9 th –10 th vs. to (9 th)10 th –13 th ray).

Etymology. The species is named after famous Japanese ichthyologist—Izumi Nakamura, who, while participating in cruises of R/V Shoyo Maru, collected all specimens of this species examined in this work.

Common names. The name “Nakamura’s flying fish” (Russian: “стрижехвост Накамуры”) is proposed here for C. izumii .

Biology. The small collection studied does not allow us to infer anything about biology of this species with any certainty. Females of C. izumii 179–188 mm SL, captured on 12 January 1988 at 20°01’S 115°00’E were close to maturity. Juveniles of C. izumii are unknown.

Distribution. Cypselurus izumii is endemic to neritic waters of South-West Australia, where it is found from 20°S to 27°S ( Fig. 3 ).

Figures

FIGURE 3. Distribution of Cypselurus starksi (□), C. oligolepis oligolepis (○), C. o. persicus (◊), C. o. georgii ( ) and C . izumii (Δ). Filled symbols indicate capture location for fishes ≤ 100 mm SL, open symbols indicate capture location for fishes> 100 mm SL. Positions of holotypes marked with asterisk.

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 19. Cypselurus izumii: (A)—187 mm SL (holotype), IORAS 03995, 20°01’S 115°00’E; (B)—pectoral fin of specimen 174 mm SL (paratype), IORAS 03997, 26°27’S 112°44’E.