Cypselurus naresii ( Günther, 1889 )

Shakhovskoy, Ilia B. & Parin, Nikolay V., 2024, A review of the flying fish genus Cypselurus (Beloniformes: Exocoetidae). Part 3. Revision of the subgenus Cypselurus sensu stricto with descriptions of one new species and four new subspecies and reinstatement of Cypselurus crockeri Seale and Exocoetus socotranus Steindachner, Zootaxa 5473 (1), pp. 1-125 : 46-60

Cypselurus naresii ( Günther, 1889)

Based mainly on chin barbel morphology we divide this highly polymorphic species into five subspecies.

Only publications in which synonymy with C. naresii is quite evident, but we are uncertain (because of insufficient morphological data provided by authors) about to which of the subspecies of C. naresii described fishes belong to, are listed here. See further bibliography below in the accounts for the subspecies of C. naresii .

Synonymy and bibliography.

Cypselurus naresii . Fowler 1934b: 394 (listed; Oceania). Munro 1958: 137 (listed; New Guinea). Parin 1961b: 118, 129, 137, 140, 165 (morphology, systematics). Parin & Besednov 1965: 111 (description of a specimen; Tonkin Bay). Munro 1967: 117 (listed; New Guinea). Parin 1967: 52, 55 (distribution). Chen 1978: 298–299 (distribution, identification key; Taiwan). Kovalevskaya 1980: 224 (listed). Kovalevskaya 1983d: 1–2 (early life history stages). Talwar & Kacker 1984: 298 (in key; India). Hutomo & Burhanuddin 1985: 28 (listed; Indonesia). Heemstra & Parin 1986: 393 (in key; referred as probable in South Africa). Fedoryako 1989b: 567 (listed). Gillett & Ianelli 1993: 178 (listed; Pacific Islands). Nguyen & Nguyen 1994: 151 ( Tonkin Bay). Parin 1996: 302, 306 [359, 363] (distribution; western Pacific; in part: except Marquesas Islands). Sommer et al. 1996: 164 (short description, figure; Somalia). Parin 1999: 2166, 2174 (distribution, diagnostic characters, figure; West-Central Pacific). Parin 2000: 600 (listed; South China Sea). Vinh 2001: 14 (listed; Vietnam). Paxton et al. 2006: 728 (distribution; Australia). Fricke et al. 2009: 30 (listed; Reunion, Mauritius, Rodrigues, Madagascar). Fricke et al. 2011: 370 (listed; New Caledonia).? Novikov et al. 2011: 205 (sighting observations; Arabian Sea). Chang et al. 2012: 543 (Taiwan). Nguyen et al. 2016: 387–391 (listed as a host of axinid parasite; Vietnam). Fricke et al. 2018: 103 (listed; Madagascar). Shakhovskoy & Collette 2022: 347–349, pl. 59 (short description, distribution; western Indian Ocean). Shakhovskoy & Parin 2022: 88–89 (comparison with C. nossibe ).

Cypsilurus naresii . Fowler 1949: 58 (listed; Oceania). Fowler 1959: 98, 99, fig. 47 (description [after Günther 1889]).

Cypselurus comatus naresii . Parin 1960b: 156 (distribution; western Pacific).

Cypselurus comatus (non Mitchell).? Sebastian & Vedavyasa Rao 1963: 322 (listed; eastern Arabian Sea)

Probable misidentifications. Tashiro (2017: 65) described C. naresii from Panay I. ( Philippines), but judging by photographs it is misidentification [probably of C. oligolepis (Bleeker) ].

Material examined. Two hundred and sixty six specimens 29–258 mm SL (see details below in the subspecies accounts).

Holotype. According to Günther (1889), the type of Exocoetus naresii , 7 inches long ( Fig. 17 ), came on board of ship on August 16, 1874 between Fiji and New Hebrides. The holotype of C. naresii was studied by the second author. Its characters are given below.

BMNH 1889.7.20.9, Fiji — Vanuatu 6. Length 137.5 mm SL. D 10, A 8, P I 13, Vert 43 (28 + 15). Measurements (in % SL): aV 61.1, cV 1 37.5, pV 36.9, c 23.5, Dc 26.1, lcir 48.0.

Diagnosis. A large, highly polymorphic species of Cypselurus having few dorsal-fin rays. Body rather deep, head and eyes large, pectoral and pelvic fins long, dorsal fin short. Jaw teeth mainly conical and with additional cusps, palatine teeth usually present. Juveniles with a long ribbon-like chin barbel and low dorsal fin, ventral side of body usually darker than dorsal one. In adults, pelvic fins usually with a large dark spot and anal fin usually with dotted pigmentation. D 9–13, Spred 26–37, Str 6½–10½, Vert 40–45 (25–30 + 13–16).

6 According to BMNH online database (www.nhm.ac.uk), the holotype was collected 6/9/1875 east of Christmas Island .

(Indian Ocean)

C. n. albitaenia (all regions) Measurements, % SL Subspecies,

SL, mm

region

io1 Hc H h Dc lP lP1 lV lD lA HD HA p lcir

182.3

79.7 18.1 18.3 7.8 24.3 70.9 43.7 39.8 17.8 10.9 9.8 14.5

- - 167.6–

68.0–91.5 (n=1) (n=1) (n=1) 24.0–24.7 70.1–71.7 42.6–44.8 38.2–41.4 (n=1) (n=1) (n=1) (n=1)

197.0 C. n. naresii

8.8 17.4 6.7 67.3 40.1 27.9 10.4 13.9

168.1 17.4 24.8 16.6 8.5 7.6 66.0 (n=2)

(n=2) (n=3) (n=3) (n=3) (n=3) (n=2) (n=3) (n=3)

120.0–212.0 (n=1) 23.5–26.1 (n=1) (n=1) (n=1) 48.0–84.1

8.6–9.1 17.2–17.7 6.4–6.8 66.8–68.1 39.3–41.3 27.8–28.0 8.9–11.9 13.2–14.6

15.9 16.4 7.7 24.6 63.2 40.2 39.0 16.8 10.1 11.5 9.3 14.2

61.1 54.6 (n=30)

- (n=18) (n=18) (n=19) (n=23) (n=25) (n=24) (n=26) (n=18) (n=18) (n=11) (n=15) (n=18)

34.5–94.0 27.7–119.0 C. n. ordinarius 14.8–17.5 14.8–19.1 7.2–8.5 23.1–26.1 58.6–68.2 36.0–43.0 37.0–42.6 15.7–17.9 8.6–11.4 10.4–12.2 8.3–10.2 13.3–15.3 (western Pacific) 8.6 17.0 18.5 7.6 24.7 67.6 42.3 31.6 16.6 9.5 10.8 7.4 14.4

160.9 25.2 (n=11)

(n=6) (n=23) (n=31) (n=26) (n=38) (n=26) (n=22) (n=27) (n=26) (n=26) (n=10) (n=15) (n=28)

102.0–218.0 7.9–89.8

7.6–9.6 15.8–18.5 17.0–21.8 6.8–8.1 22.7–26.0 62.9–70.7 37.4–48.9 26.7–36.2 14.5–19.0 6.8–11.5 10.1–12.0 6.6–8.5 12.9–15.9

16.2 16.3 7.8 25.1 64.8 41.3 39.8 17.2 10.3 12.5 9.5 15.1

59.0 65.3 (n=5)

- (n=3) (n=3) (n=3) (n=5) (n=5) (n=5) (n=5) (n=3) (n=3) (n=3) (n=4) (n=3) C. n. ordinarius 29.0–93.5 15.5–16.6 15.7–16.6 7.5–8.1 24.2–25.6 61.3–69.7 38.9–43.8 37.2–43.5 16.1–18.0 8.9–11.6 12.0–13.0 8.2–10.2 14.9–15.4 45.0–93.1 (eastern Indian Ocean) 156.1 17.0 18.0 7.4 24.2 67.7 42.6 33.6 16.3 9.6 10.9 7.6 13.8 36.1 (n=10)

- (n=15) (n=13) (n=15) (n=16) (n=10) (n=11) (n=13) (n=15) (n=15) (n=2) (n=9) (n=15)

103.5–240.0 8.8–113.7

16.3–18.6 16.7–22.0 6.7–8.2 22.0–26.3 63.3–70.4 39.1–49.0 28.6–39.6 15.0–18.4 7.8–11.0 10.4–11.5 6.7–8.5 12.5–15.3

15.9 16.2 7.5 25.0 63.8 40.4 40.3 17.5 10.7 11.7 9.4 14.3

61.4 61.9 (n=15) C. n. ordinarius 41.0–96.0 - (n=11) (n=11) (n=11) (n=14) (n=12) (n=13) (n=12) (n=11) (n=11) (n=2) (n=6) (n=11) 24.7–127.0 (Bay of Bengal 14.6–17.0 14.6–17.8 6.9–8.2 24.1–26.1 59.5–70.0 36.1–45.5 37.1–44.1 16.3–19.4 9.2–11.5 11.6–11.9 8.0–10.2 13.1–14.8 and Andaman 17.7 19.3 7.6 24.4 68.3 42.6 29.3 16.7 8.8 10.0 7.1 14.2

185.5 8.2 21.2 (n=6) Sea) (n=33) (n=27) (n=46) (n=41) (n=34) (n=36) (n=31) (n=35) (n=36) (n=15) (n=23) (n=35)

101.0–215.0 (n=1) 10.4–31.6

16.6–19.2 17.0–21.7 6.8–8.1 22.6–26.4 63.4–70.6 38.1–47.5 26.5–37.4 15.0–18.7 7.2–10.4 8.6–10.9 6.0–8.6 13.1–15.9

15.9 16.3 7.6 24.8 63.6 40.4 39.4 17.1 10.3 11.7 9.3 14.3

60.9 57.9 (n=50)

- (n=32) (n=32) (n=33) (n=42) (n=42) (n=42) (n=43) (n=32) (n=32) (n=16) (n=25) (n=32)

29.0–96.0 24.7–127.0 C. n. ordinarius 14.6–17.5 14.6–19.1 6.9–8.5 23.1–26.1 58.6–70.0 36.0–45.5 37.0–44.1 15.7–19.4 8.6–11.6 10.4–13.0 8.0–10.2 13.1–15.4 (all regions) 8.5 17.3 18.7 7.6 24.5 67.9 42.5 31.0 16.6 9.2 10.4 7.3 14.2

171.8 28.3 (n=27)

(n=7) (n=71) (n=71) (n=87) (n=95) (n=70) (n=69) (n=71) (n=76) (n=77) (n=27) (n=47) (n=78)

101.0–240.0 7.9–113.7

7.6–9.6 15.8–19.2 16.7–22.0 6.7–8.2 22.0–26.4 62.9–70.7 37.4–49.0 26.5–39.6 14.5–19.0 6.8–11.5 8.6–12.0 6.0–8.6 12.5–15.9

12.1

18.7 36.6 10.8 8.6 C. n. 45.2 17.9 7.7 26.2 57.6 18.9 (n=3) 15.3 11.8

- (n=3) - (n=3) (n=2) (n=2) septentrionalis a 33.0–55.1 (n=1) 7.4–8.4 24.2–27.5 50.5–63.1 17.9–20.0 10.9– 14.3–16.3 8.3–17.9

17.9–19.9 35.9–37.4 9.5–12.1 7.7–9.5

13.3

......continued on the next page

Measurements, % SL

Subspecies,

SL, mm

region

io1 Hc H h Dc lP lP1 lV lD lA HD HA p lcir 16.9 19.2 7.5 67.4 43.3 30.2 17.3 9.4 10.8 7.6 13.7

C. n. albitaenia 208.6 7.8 25.3 24.4 (n=2) (n=10) (n=12) (n=11) (n=13) (n=9) (n=14) (n=11) (n=11) (n=3) (n=5) (n=10)

(Arabian sea) 114.0–256.0 (n=1) 23.6–27.1 20.9–28.0 16.2–18.5 16.8–21.5 7.0–8.1 64.4–70.1 38.0–47.8 26.1–37.1 15.2–18.5 8.0–10.9 10.4–11.1 7.0–8.0 13.2–14.3

16.6 17.2 7.9 25.0 65.5 42.9 40.5 17.0 10.0 11.3 9.9 14.7

65.7 56.2 (n=9) - (n=8) (n=8) (n=8) (n=9) (n=8) (n=8) (n=8) (n=8) (n=8) (n=4) (n=8) (n=8)

50.0–92.0 22.8–76.6

C. n. albitaenia 16.0–17.7 16.2–18.4 7.2–8.4 24.3–25.9 62.3–68.8 38.8–45.4 38.9–41.5 16.3–17.6 8.9–10.9 10.8–11.7 8.5–11.2 14.4–15.8

(Indian Ocean) 16.6 17.9 7.3 24.5 68.4 42.6 31.0 16.3 8.9 10.1 7.0 13.6

191.4 26.3 (n=14) - (n=29) (n=27) (n=29) (n=42) (n=26) (n=29) (n=29) (n=30) (n=30) (n=11) (n=15) (n=27)

101.0–258.0 7.7–49.0 15.3–18.1 15.9–20.1 6.6–8.6 22.3–26.6 65.4–72.4 38.2–46.5 25.9–39.4 14.0–18.4 6.6–10.3 8.7–11.1 5.4–9.1 12.3–15.1

16.6 17.2 7.9 25.0 65.5 42.9 40.5 17.0 10.0 11.3 9.9 14.7

65.7 56.2 (n=9) - (n=8) (n=8) (n=8) (n=9) (n=8) (n=8) (n=8) (n=8) (n=8) (n=4) (n=8) (n=8)

50.0–92.0 22.8–76.6

C. n. albitaenia 16.0–17.7 16.2–18.4 7.2–8.4 24.3–25.9 62.3–68.8 38.8–45.4 38.9–41.5 16.3–17.6 8.9–10.9 10.8–11.7 8.5–11.2 14.4–15.8

(all regions) 16.7 18.3 7.3 24.7 68.1 42.8 30.7 16.6 9.0 10.2 7.1 13.6

195.8 7.8 26.1 (n=16) (n=39) (n=39) (n=40) (n=57) (n=39) (n=38) (n=43) (n=41) (n=41) (n=14) (n=20) (n=37)

101.0–258.0 (n=1) 7.7–49.0 15.3–18.5 15.9–21.5 6.6–8.6 22.3–27.1 64.4–72.4 38.0–47.8 25.9–39.4 14.0–18.5 6.6–10.9 8.7–11.1 5.4–9.1 12.3–15.1

51.0 - - - - - - - - - - - - - -

C. n. socotranus b 8.6 16.7 18.4 7.2 25.8 68.0 43.4 28.5 17.7 9.8 10.9 7.0 15.1

143.3

(n=5) (n=9) (n=14) (n=14) (n=14) (n=14) (n=9) (n=13) (n=14) (n=14) (n=10) (n=13) (n=13) 3.9 (n=1)

109.0–182.0

7.6–9.5 16.1–17.5 16.4–20.4 6.0–7.7 25.1–27.3 64.8–72.7 40.4–46.9 24.7–32.0 16.3–18.7 8.5–12.1 9.2–11.6 5.4–8.0 13.8–16.3

a Data of Chen (1987) are also included.

b Data of Kotthaus (1969) and Shakhovskoy & Bogorodsky (2021) are also included.

Description. Meristic and morphometric characters are given in Tables 1–7, 10 and 14. D 9–13 (usually 11–12), A 6–10 (usually 8–9), P I 12–15 (usually I 13–14), Spred 26–37 (usually 28–32), Str 6½–10½ (usually 7½–8½), Sp.br 19–28 (4–8 + 14–20), usually 21–25 (5–7 + 16–18), Vert 40–45 (25–30 + 13–16), usually 41–43 (27–29 + 14–15). Snout moderate ( Figs. 18–19 ), lower jaw usually shorter than upper jaw, sometimes jaws of equal size or lower jaw slightly longer (in juveniles <140 mm SL lower jaw usually a bit longer than upper one). Upper jaw not pointed anteriorly ( Figs. 18–19 ). Juveniles <110–170 mm SL (the smallest fish without a barbel is 109 mm SL and the largest fish with a barbel is 173 mm SL) with a long ribbon-like chin barbel ( Figs. 18a–b , 19a–d ), usually protruding beyond pectoral-fin base and in some fish nearly twice as long as the body length ( Figs. 4f , 20 ); in largest barbelled juveniles> 150 mm SL the barbel reaches from eye origin to head posterior margin (rarely slightly beyond). The chin barbel has a thick median keel along the full length and two triangular lobes basally (absent in C. n. septentrionalis), its end is usually expanded and slightly emarginated; in juveniles> 100 mm SL barbel usually tapered distally. However, there is a great deal of variation in the barbel size, shape and pigmentation, as well as in the size of body at which juveniles lose their barbel (see below in the subspecies accounts). Jaw teeth not numerous, small to medium-sized (not visible or barely visible to naked eyes), mainly conical and/or with additional cusps, few tricuspid teeth may also be present (in some fish tricuspid teeth prevail); juveniles <90 mm SL usually with conical teeth only. Teeth arranged in 1–2 (in adults rarely in 3) rows. Palatine teeth usually present (absent in 13 of 189 specimens studied), sparse.

Body elongate in juveniles, deeper in adults ( Fig. 20b ): in juveniles 40–140 mm SL body depth 5.0– 6.85 in SL; in fish 140–260 mm SL, 4.55–6.3 in SL. Body width 1.00–1.54 and caudal peduncle depth 1.93–3.02 in greatest body depth. Greatest head depth slightly increasing with growth: in juveniles 40–140 mm SL, 5.5–6.85 in SL and in fish 140–260 mm SL, 5.2–6.55 in SL. Head length not changing with growth, 3.7–4.4 in SL and 0.89–1.14 in dorso-caudal distance. Eyes large, eye diameter decreasing with growth: in juveniles 40–140 mm SL eye 10.3–14.7 in SL, 2.5–3.55 in head length, 0.9–1.45 in interorbital width and 1.05–1.75 in postorbital distance; in fish 140–260 mm SL, 11.6–16.4 in SL, 2.9–3.8 in c, 1.05–1.4 in io and 1.3–1.95 in po. Snout length barely increasing with growth.

Pectoral fins long, their length increasing with growth to about 100 mm SL, and afterwards nearly constant ( Fig. 4c ): in juveniles 40–140 mm SL pectoral fin 1.35–2.0 in SL and in fish 140–260 mm SL, 1.35–1.6 in SL. Tip of pectoral fin reaching from end of dorsal-fin base to origin of caudal-fin upper lobe; in juveniles 30–65 mm SL from middle to end of dorsal-fin base. First pectoral-fin ray unbranched, its length hardly changing with growth ( Fig. 4d ), 2.05–2.8 in SL and 1.44–1.75 in lP. Pelvic-fin base about midway ( Fig. 4a ) between posterior edge of head and origin of caudal-fin lower lobe or closer to the latter (cV / pV = 0.88–1.22); in C. n. septentrionalis closer to the head (cV / pV = 0.81–0.89). Pelvic-fin length decreasing strongly with growth ( Fig. 20c ): in juveniles 40–140 mm SL pelvic fin 2.25–3.3 in SL and 1.35–2.32 in lP; in fish 140–260 mm SL, 2.65–4.05 in SL and 1.82–2.62 in lP. However, there is some variation in pelvic-fin length among different subspecies ( Fig. 20c ). Tip of pelvic fin in juveniles 30–120 mm SL protruding beyond origin of caudal-fin lower lobe. In fish 120–160 mm SL from middle of caudal peduncle to origin of caudal-fin lower lobe (sometimes slightly beyond). In fish ≥ 160 mm SL from end of anal-fin base (or nearly so) to middle of caudal peduncle. However, in C. n. socotranus 109–162 mm SL pelvic fins reaching not further than slightly beyond end of anal-fin base.

Anal-fin origin far posterior to dorsal-fin origin (1st anal-fin ray under 4th–7th dorsal-fin ray, usually under 5th– 6th). Dorsal fin with 1–5 (usually 3–4) rays more than anal fin. Height of dorsal ( Fig. 4e ) and anal fins decreasing with growth: in juveniles 40–140 mm SL HD 7.7–9.67 in SL and HA 8.9–14.9 in SL; in fish 140–260 mm SL, HD 8.3–13.0 in SL and HA 11.75–18.5 in SL. Longest dorsal- and anal-fin ray—2nd or 3rd. In juveniles 30–80 mm SL tip of last dorsal-fin ray reaching (nearly reaching) origin of caudal-fin upper lobe or protruding slightly beyond; middle and posterior rays of dorsal fin not elongated, penultimate rays not extending or only slightly extending beyond tip of last ray ( Fig. 19 ). In fish> 80 mm SL tip of last dorsal-fin ray reaching from middle of caudal peduncle to origin of caudal-fin upper lobe, tips of penultimate rays ahead of it.

Pigmentation. Body of juveniles 40–85 mm SL pale brown to dark brown ( Fig. 19a–b ), ventral side usually darker than dorsal one, in some fish it has a golden or silvery shine. Body bands always absent. In juveniles> 85 mm SL body grow paler ventrally, and majority of fish> 120 mm SL with typical adult “pelagic” pigmentation. However, there is divergence from the above general pattern: juveniles of C. n. albitaenia 50–85 mm SL differ in having extensive pale patch on ventral side of body anteriorly ( Fig. 21 ), and juveniles of C. n. septentrionalis have “pelagic” pigmentation as early as 33–44 mm SL.

7 According to Chen (1987), in a specimen of C. naresii 48.9 mm SL, HD fits 10.5 times in SL.

In juveniles 30–90 mm SL, head with a wide dark brown longitudinal stripe through the eye ( Figs. 18a , 19a–b ). However, in juveniles of C. n. septentrionalis 33–44 mm SL the stripe is absent (head silvery), and according to Chen (1987) it appears at about 50 mm SL. The ventral surface of the head in juveniles 30–80 mm SL is generally more or less densely covered with melanophores (only distal parts of branchiostegal rays and margin of gill covers pale) with chin area especially densely pigmented ( Fig. 21a ). In juveniles of C. n. albitaenia ( Fig. 21b ) and C. n. septentrionalis the ventral surface of the head is much paler, with pigmentation mainly on the chin; the pattern of head pigmentation for juveniles of C. n. socotranus is unknown. In fish 80–120 mm SL pigmentation starts to disappear, persisting longest on chin, and in fish> 120 mm SL lower surface of head mostly pale. A few small dark specks may be present on gill cover and/or under eye, but the specks are probably covered with iridocytes in life.

Chin barbel pigmentation varies among subspecies of C. naresii ( Fig. 22 ). In juveniles of C. n. ordinarius barbel brown to dark brown (sometimes nearly black) with a pale median keel (in juveniles <110 mm SL the keel usually densely pigmented terminally, matching pigmentation of barbel’s broadened distal part) and, in some fish, a narrow pale terminal edging ( Fig. 18a ). Opposite (ventral) side of barbel similarly pigmented, but usually more intensely, with at most a trace of pale line along the keel (if any). Juveniles of C. n. albitaenia 50–90 mm SL have a pale longitudinal streak distally (in some juveniles the streak is so wide and long that barbel looks mainly pale); however, in larger juveniles the barbel is similar to C. n. ordinarius ( Fig. 22d–f ). In juveniles of C. n. naresii the pigmentation is similar to C. n. ordinarius, but the barbel is typically paler at its end. In C. n. septentrionalis chin barbel entirely brown or dark brown with paler base; the keel is concolor with barbel or only slightly paler. In two barbelled specimens of C. n. socotranus 51 and 121 mm SL barbel mainly pale with dark pigmentation only laterally, barbel’s tip entirely pale. Opposite (ventral) side of the barbel in a 121 mm SL specimen is brown proximally and pale with only few melanophores near lateral margins distally.

Pectoral fins in juveniles and adults ( Figs. 18a–c , 23a–d ) pale brown to dark brown (sometimes nearly black) to 7th–10th ray (pigmentation usually extending one ray lower distally than proximally, occasionally a subtle “mirror” present), usually with a pale tip and, in adults, pale posterior edging. In adults pectoral fins sometimes have a violet tinge, and in some fish pigmentation is faded proximally. There is some variation among subspecies in pectoral-fin pigmentation of juveniles 30–85 mm SL: in C. n. ordinarius pigmentation spreads to 7th–8th (occasionally to 9th) ray (in Pacific specimens usually to 7th ray and in Indian Ocean specimens usually to 8th ray), and in C. n. septentrionalis, C. n. naresii and C. n. albitaenia to 9th (occasionally to 10th) ray.

Pelvic fins of juveniles 30–65 mm SL entirely brown to dark brown (sometimes nearly black), usually with pale tips of outer and inner rays ( Fig. 18a ). In juveniles> 65 mm SL pigmentation starts to disappear between 5th–6th rays and along 1st ray ( Fig. 23e ), and in fish> 100 mm SL also near pelvic-fin base ( Fig. 23f–g ). In fish> 155 mm SL ( Fig. 23h ) pelvic fins pale with a large pale brown to dark brown spot between 2nd or 3rd and 4th or 5th rays distally (but in some fish pelvic fins remain mainly dark up to 170 mm SL). In few adults the dark spot degraded to merely aggregation of dots.

Dorsal fin of juveniles 30–100 mm SL more or less densely covered with brown melanophores (usually denser in the upper part and, in some fish, also near the fin base anteriorly) ( Fig. 18a ). In fish> 100 mm SL dorsal fin gray to pale-brownish (in some fish, especially 100–170 mm SL, with darker upper margin).

Anal fin of juveniles 30–115(130) mm SL pale with brown pigmentation near fin base anteriorly (absent in C. n. albitaenia) and in the posterior part (in some fish anal fin much darker—brown with paler base and anterior rays distally) ( Fig. 18a–b ). In fish> 115 mm SL usually only dotted pigmentation persists in the lower part of anal fin, which is usually retained as sparse dots even in largest adults (in few fish anal fin entirely devoid of pigmentation). However, in C. n. socotranus anal fin fully unpigmented starting with 123 mm SL.

Caudal fin of juveniles 30–40 mm SL pale with pale brown to brown base and brown dotted pigmentation along lower lobe rays and, in fish about 40 mm SL, also sparser pigmentation on upper lobe. Juveniles 40–110 mm SL usually with 1–2 dark bands on lower lobe and, starting with 60 mm SL, also with 1–2 dark bands on upper lobe ( Figs. 18a–b , 19b–c ). However, in C. n. albitaenia dark bands on caudal-fin lobes appear only in fish> 60 mm SL (as many as 3 dark bands on lower lobe may be present). In fish> 110 mm SL caudal fin pale brown to brown ( Fig. 19d–f ), sometimes with slightly darker fin base and tip of upper lobe and slightly paler fork. In some fish dark bands may be retained up to 155 mm SL.

Coloration in life. According to observations of the second author, a juvenile of C. n. ordinarius 41 mm SL (IORAS 04229) in life had goldish pigmentation on sides and belly, dorsal fin was reddish, other fins black and white; a juvenile 56 mm SL (IORAS 04139) was with orange bands on caudal-fin lower lobe. Imai (1959) reported that juveniles of C. naresii (septentrionalis) about 10 mm long, captured near Yaku Island, Japan among an aggregation of Trichodesmium sp. , had red coloration from back to body sides (except rear of caudal peduncle), with silverywhite pigmentation only on sides of belly.

Maximum size. The maximum length of C. naresii in the material examined was 258 mm SL ( ZMUC, uncat., 9°31’S 49°29’E, not dissected for sex). The largest female was 254 mm SL ( IORAS 04151 ) and the largest male 226 mm SL ( IORAS 04432 ) .

Intraspecific variation. Based mainly on chin barbel morphology and pigmentation we recognize five, allopatric (although a slight overlap of some areas exists), subspecies of C. naresii : C. n. naresii from waters of East Australia and western Polynesia, C. n. ordinarius from the eastern Indian and western Pacific oceans, C. n. septentrionalis from the north-western Pacific, C. n. albitaenia from the western and central Indian Ocean and C. n. socotranus from Gulf of Aden and adjacent waters of the Red Sea and Indian Ocean. Although C. n. ordinarius is the most common and widespread subspecies, the nominotypical taxon should be peripheral subspecies from the south-western Pacific, as the type of C. naresii was described by Günther (1889) from there. Two most aberrant subspecies, C. n. septentrionalis and C. n. socotranus , may deserve full species rank and further research is needed.

Comparative remarks. Cypselurus naresii differs from C. hiraii in fewer vertebrae, dorsal-fin rays, transverse scales and gill rakers (see Tables 1–2, 4–6), longer head (22.8–26.8, usually> 24.0 vs. 21.2–24.7, usually <24.0% SL), larger eye (in fish ≥ 150 mm SL eye diameter 6.1–8.6, usually> 7.0 vs. 6.0–6.9% SL), smaller dorso-caudal distance (22.0–27.5, usually <26.0 vs. 24.8–29.6, usually> 26.0% SL, see Fig. 4b ), deeper caudal peduncle (in fish ≥ 150 mm SL, h 6.0–8.6, usually ≥ 7.0 vs. 5.5–6.9% SL), longer chin barbel in juveniles ( Fig. 4f ) and in other characters (see Table 7). There are also differences in pigmentation: adults of C. naresii with pigmented pelvic and anal (except C. n. socotranus ) fins while in C. hiraii pelvic fins are pale in fish> 185 mm SL and anal fin devoid of pigmentation in fish> 160 mm SL.

Cypselurus naresii is very similar to C. opisthopus in adult stage (however, the former species has much larger maximal size—258 vs. 186 mm SL). Cypselurus naresii differs in a more anterior position of pelvic-fin base (index cV/pV 0.81–1.22, usually <1.10 vs. 1.04–1.46, usually> 1.10, see Fig. 4a ), longer pectoral ( Fig. 4c–d ) and pelvic fins (in fish 140–185 mm SL (except C. n. socotranus ), lV 27.4–37.5, usually> 30 vs. 26.0–36.8, usually <30% SL), and in denser pigmentation of pelvic and anal fins (except C. o. crockeri ) and fewer dark specks on head sides. Juveniles of C. naresii are easily distinguishable from C. opisthopus by a longer chin barbel (except C. n. septentrionalis) ( Fig. 4f ), lower dorsal fin ( Fig. 4e ), longer snout (in fish 30–110 mm SL, ao 3.4–5.7, usually> 4.0 vs. 2.6–4.3, usually <4.0% SL) and pigmentation of caudal, pectoral, pelvic, dorsal and anal fins (see descriptions above).

Cypselurus naresii differs from C. nossibe in slightly fewer pectoral-fin rays (13–16, usually ≤ 15 vs. 15–17, usually 16) and more predorsal scales (26–37, usually ≥ 28 vs. 26–30, usually ≤ 28), shorter dorsal fin originating more posteriorly (lD 14.0–20.0, usually <18.0 vs. 18.0–21.2% SL; aD 68.8–75.5, usually> 72.2 vs. 68.4–72.2% SL; Dc 22.0–27.5, usually <26.0 vs.26.0–28.4% SL) and smaller eye (6.1–9.7, usually <8.5 vs. 8.5–10.8% SL). Adults also differ in jaw teeth morphology (mainly conical and with additional cusps in C. naresii vs. mainly tricuspid teeth in C. nossibe ), and juveniles in chin barbel morphology (long with a median keel in C. naresii vs. diminutive without a keel in C. nossibe ), pectoral-fin pigmentation (without vs. with a row of pale spots), dorsal fin height (in fish <125 mm SL, HD 9.5–13.0% SL, middle and posterior rays not elongated vs. HD 12.7–15.5% SL, middle and posterior rays elongated), snout length (in fish ≤ 120 mm SL, ao 3.4–5.7, usually> 4.2% SL vs. 2.3–4.2% SL), interorbital width (in fish <125 mm SL, io 7.6–10.4% SL vs. 10.2–12.7% SL) and head depth (in fish <125 mm SL, Hc 14.6–18.1, usually <17.5% SL vs. 17.6–19.6% SL).

From all species of the subgenus Poecilocypselurus , C. naresii differs in the presence of chin barbel in juveniles, more posterior position of pelvic-fin base (index cV/pV 0.81–1.22, usually> 0.90 (except C. n. septentrionalis) vs. 0.48–1.05, usually <0.90 [except C. neglectus shcherbachevi and C. callopterus (Günther) ], pigmentation of pelvic fins in adults (usually with large spot distally vs. usually pale) and jaw teeth morphology (mainly conical and with additional cusps vs. mainly tricuspid [except C. bosha and C. olpar ]).

Biology. Females are mature starting with 191 mm SL in the Bay of Bengal and 211 mm SL in the waters of Vietnam. Females of C. n. albitaenia mature at a much larger size—starting with about 240 mm SL. Close to mature females were captured in the western Indian Ocean in December and January ( IORAS 04171 , IORAS 04197 ) , off eastern Sri Lanka in April ( IORAS 04277 ) and in the Bay of Bengal in June– July ( IORAS 04260 ) . Larvae and early juveniles 11–15 mm SL were captured in May ( MCZ 155992 , 16°00’N 62°01’E; MCZ 155982 , 22°17’N 60°44’E) ; small juveniles about 30 mm SL were captured south of Java in March ( IORAS 04234 ) , north of Taiwan in late May ( ZMUC P341435 – P341437 ) and south of Japan in July ( IORAS 04251 ) .

Imai (1955) reported that spawning takes place in June–July near the coast of Kyushu. According to Chen (1987), larvae of C. naresii appeared in the waters off South-West Taiwan in late March, off North Taiwan in mid May, in the East China Sea in June–July, and off Boso Peninsula, Japan in mid August. Sea surface temperature was 25.8–29.0°C (the majority of larvae were captured at 25.8–27.0°C). A juvenile 23.2 mm was caught in Tokyo Bay on 24.07.2017 ( Arao et al. 2020).

According to Lakshminaraina (1993), all adult C. naresii captured off Coramandel Coast of India in June and July were mature. Mean length and weight of females were higher than that of males— 216 mm FL and 144.9 g vs. 202 mm FL and 106.6 g, respectively. Females had larger maximal size than males—230 vs. 212 mm FL, respectively ( Andrianov & Lakshminaraina 1994). These authors suggested spawning of C. naresii in the waters of SE India at least in June–July. Thus, the spawning season of C. naresii seems to be protracted at least from December to July–August but probably has some variability in different subspecies and localities.

Distribution. Distribution of C. naresii and its subspecies is given in Fig. 24 . This polytypic species is distributed mainly in neritic waters (but C. n. albitaenia occurs mainly in oceanic waters) from east Africa, southern Red Sea and Gulf of Oman to waters of South-East Australia, western Polynesia and Japan. Additional records of C. naresii are listed in the Synonymy and bibliography sections (see above and below). Fricke et al. (2009) listed C. naresii for the waters of Reunion, Mauritius, Rodrigues and Madagascar.

Nguyen et al. 2016 reported C. naresii from Vietnam (21°26’N 107°59’E, 17°35’N 107°08’E, 16°42’N 108°19’E). However, this work, devoted to systematics of Monogenea parasites, contains no figures or measurements for the host species C. naresii . Parin (1996) reported C. naresii for Marquesas Islands, but we re-identified all specimens from these islands as C. angusticeps .

Figures

FIGURE 4. Size variation of morphometric characters (in % SL) in Cypselurus hiraii (◊), C. opisthopus (∆), C. naresii (○), C. persimilis (+), C. angusticeps (□) and C. comatus (x): (A)—cephalo-ventral distance divided by postventral distance (index cV/ pV); (B)—dorso-caudal distance (Dc); (C)—pectoral-fin length (lP); (D)—length of the first pectoral-fin ray (lP1); (E)—height of dorsal fin (HD); (F)—length of chin barbel (Lcir).

FIGURE 17. Holotype of Cypselurus naresii, 137.5 mm SL, BMNH 1889.7.20.9, Fiji—Vanuatu (after Günther 1889).

FIGURE 18. Cypselurus naresii ordinarius. (A)—42 mm SL, IORAS 04227, 5°00’N 90°52’E (drawing by G.N. Pokhilskaya); (B)—68 mm SL, IORAS 04232, 1°57’N 135°14’E (after Parin 1961a); (C)—196 mm SL, IORAS uncat., 3°06’N 128°09’E (after Parin 1961a).

FIGURE 19. Cypselurus naresii ordinarius. (A)—47.5 mm SL, IORAS 04209, 0°59’N 134°31’E; (B)—68 mm SL, IORAS 04255, 9°29’N 89°54’E; (C)—103.5 mm SL, IORAS 04241, 10°03’S 108°00’E; (D)—144 mm SL, IORAS 04245, 9°00’S 105°24’E; (E)—176 mm SL (flipped horizontally), ZMMU P-24607 (holotype), 9°20’S 111°53’E; (F)—207 mm SL, IORAS 04277, 6°33’N 82°18’E.

FIGURE 21. Ventral side of head in juveniles of Cypselurus naresii. (A)—C. n. ordinarius, 55 mm SL, IORAS 04228, 8°18’N 120°25’E; (B)—C. n. albitaenia, 56 mm SL, IORAS 04224, 4°30’S 75°00’E.

FIGURE 22. Chin barbel of Cypselurus naresii ordinarius (A–C) and C. n. albitaenia (D–F) (ventral view of head). (A)—51.5 mm SL, IORAS 04222, 10°48’S 104°38’E; (B)—78 mm SL, IORAS 04223, 6°20’N 122°36’E; (C)—121 mm SL, IORAS 04244, 5°38’S 147°04’E; (D)—53 mm SL, IORAS 04224, 4°30’S 75°00’E; (E)—86 mm SL, IORAS 04247, 7°10’S 67°39’E; (F)—168 mm SL, IORAS 04211, 6°44’S 59°16’E.

FIGURE 23. Pectoral (A–D) and pelvic (E–H) fins of Cypselurus naresii ordinarius. (A)—60 mm SL, IORAS 04244, 5°38’S 147°04’E; (B) & (E)—78 mm SL, IORAS 04223, 6°20’N 122°36’E; (C) & (F)—112 mm SL, IORAS 04216, 7°48’N 95°11’E; (D) & (H)—207 mm SL, IORAS 04277, 6°33’N 82°18’E; (G)—141 mm SL, IORAS 04244, 5°38’S 147°04’E.

FIGURE 24.Distribution of Cypselurus naresii (∆—C.n.naresii, —C.n. septentrionalis (our data), —C. n. septentrionalis (data of Imai 1959, Tsukahara 1959 and Chen 1987), ○—C. n. ordinarius, ◊—C. n. albitaenia, □—C. n. socotranus). Filled symbols indicate capture location for fishes ≤ 100 mm SL, open symbols indicate capture location for fishes> 100 mm SL; holotype position marked with asterisk.

FIGURE20.Sizevariationofmorphometriccharacters(in%SL)inCypselurusnaresii:x—C.n.naresii;◊—C.n.septentrionalis; □—C. n. socotranus; Δ—C. n. ordinarius (lilac—western Pacific Ocean, red—eastern Indian Ocean, orange—Bay of Bengal and Andaman Sea); ○—C. n. albitaenia (dark blue—Indian Ocean, light blue—Arabian Sea). (A)—preventral distance (aV); (B)—greatest body depth (H); (C)—pelvic-fin length (lV); (D)—length of chin barbel (Lcir).