Cheilopogon (Ptenichthys), 1843

Shakhovskoy, Ilia B. & Parin, Nikolay V., 2019, A review of the flying fish genus Cypselurus (Beloniformes: Exocoetidae). Part 1. Revision of the subgenus Zonocypselurus Parin and Bogorodsky, 2011 with descriptions of one new subgenus, four new species and two new subspecies and reinstatement of one species as valid, Zootaxa 4589 (1), pp. 1-71 : 37-43

Cheilopogon (Ptenichthys) sp.1

( Figs. 3 , 15a , 16 , 17 a–b, 18; Tables 1–8)

Cypselurus hexazona (non Bleeker). Parin & Bogorodsky 2011: 683–686 [658–660 in English translation] (in part; description, distribution (Western Australia )).

Juveniles of this species (or these species?) were identified in many collections as C. hexazona . However, their belonging to the subgenus Ptenichthys of the genus Cheilopogon does not give us any doubt, because some specimens have tiny chin barbels of a form characteristic for the subgenus, which, being usually tightly pressed to the lower jaw, may be overlooked if a fish is not carefully studied. These barbels are probably either easily broken off in life or are absent in some fish (there is dimorphism).

Material examined. Sixteen specimens 33–103 mm SL.

Full morphological study. WAM P.52-001 (1, 33 mm SL), 32°03’S 115°44’E . WAM P.6208-001 (1, 48 mm SL), 28°45’S 113°50’E, March 1964 . WAM P.16518 (1, 59 mm SL), Shark Bay , June 1963 . FRSKU 113559 (1, 82.5 mm SL), 20°00’S 116°59’E, 9.01.1989 . FRSKU 114540 (8, 43– 65 mm SL), 20°00’S 117°04’E .

Partial morphological study. CSIRO C.1705 (1, 99 mm SL), 12°02’S, 128°51’E, 12.10.1949 . CSIRO C.3097* (1, 103 mm SL), 12°02’S 128°51’E, 12.10.1949 . AMS I.21634-003* (2, 54– 59 mm SL), 11°42’S 127°29’E, 2.07.1979 .

Description. Meristic and morphometric characters are given in Tables 1–8. D 12–13, A 9–10, P I 13–15 (usually I 14–15), Spred 27–32, Str 8½–10 (usually 9–9½), Sp.br 21–24 (6–7 + 15–17), Vert 45 (29 + 16). Palatine teeth absent in all examined specimens. Snout relatively short, upper jaw usually slightly pointed at tip. Lower jaw slightly longer than upper jaw or, less frequently, equal to it. Juveniles to 52.5 mm SL with pair of tiny, thin barbels on chin (posterior to the symphysis, see Fig. 15a ), which are slightly enlarged and rounded at the end. Length of barbels only 2.0–4.4% of SL. Apparently these barbels are easily lost, because 3 of 9 specimens of this size had no barbels. There are no barbels in juveniles 54 mm SL and longer. Jaw teeth few, small and conical, arranged in 1–2 rows. Only one specimen with a single tooth with additional cusps.

The body is elongate in fish 33–103 mm SL. The greatest body depth 5.35–6.7 in SL. Body width 1.13–1.33 and depth of caudal peduncle 2.10–2.73 in greatest body depth. Greatest head depth and head length 5.9–6.7 and 4.0– 4.6 in SL, respectively. Head length 1.12–1.41 in dorso-caudal distance. Eyes large, their diameter 9.45–12.5 in SL, 2.28–2.84 in c and 0.85–1.17 in io.

Pectoral fins relatively short, their length 1.4–1.6 in SL. Tip of fin usually nearly reaches end of dorsal-fin base or (usually in fish from higher latitude waters) protrudes only slightly beyond it, not reaching middle of caudal peduncle. First pectoral-fin ray unbranched, its length 2.4–3.0 in SL and 1.7–1.9 in lP.

Pelvic fin base much closer to posterior edge of head than to origin of caudal fin lower lobe (cV/pV = 0.59– 0.76). Pelvic fin length decreases quite markedly as fish grows, 2.05–2.6 in SL and 1.3–1.75 in lP. Tip of pelvic fin always extends beyond origin of lower lobe of caudal fin.

Anal-fin origin far behind dorsal-fin origin (the 1st anal-fin ray below 4th–6th dorsal-fin ray). Dorsal fin with 2–4 rays more than anal fin; height of dorsal and anal fins 6.5–8.2 and 8.05–9.8 in SL, respectively. Longest dorsalfin ray usually the 2nd (occasionally the 3rd); the 3rd or, rarely, the 2nd anal-fin ray longest. Tip of last dorsal-fin ray reaches (or almost reaches) middle of caudal peduncle or slightly beyond. Middle and posterior dorsal-fin rays not elongate.

Pigmentation. Fish 33–82.5 mm SL with 5 bands on the body ( Figs. 15a , 16 ): near pectoral-fin base, between pectoral and pelvic fins, near pelvic-fin base, near anus, and above middle of anal-fin base (last 2 bands are often barely visible). Aggregations of melanophores on gill covers and near base of caudal fin, when dense, can also be interpreted as bands. Dark band under eye is usually not present or very weak. Posterior part of body along midline with streak formed by aggregation of melanophores. Underside of head pale, sometimes with solitary dots on branchiostegal rays. Fish 96 mm SL and longer without body bands.

Note to Table 8: Nos. 1-4, 5-7 and 10—FRSKU 114540, Nos. 8–9—AMS I.21634-003, No. 11—FRSKU 113559, No. 12 —AMS C.1705, No. 13—CSIRO C.3097, No. 14—WAM P.52-001, No. 15—WAM P.6208-001, No. 16—AMS P.16518. Sign «+» means that barbel was damaged. Nos. 14–16 are fishes from higher latitudes.

Pectoral fins ( Figs. 17 a–b) of juveniles 33–82.5 mm SL mottled, with alternating pale and dark areas: large dark brown spot distally along lower edge of fin, and dark transverse band near base; somewhat more posteriorly a second transverse band (sometimes interrupted in middle) formed by a large dark spot above (which can merge with the first band) and a smaller spot below, with less pigmentation between these spots. Also, below tip of first pectoral-fin ray there is dark oblong spot between 1st and 3rd–5th rays. Remainder of fin is almost unpigmented,with only rare dots. First two bands on folded pectoral fin align with bands on body. In fish 96–103 mm SL pigmented areas on the proximal part of fin merged and fin dark with wide, oblique, pale band reaching upper margin of fin.

Pelvic fins ( Figs. 17a, b ) of juveniles 33–65 mm SL brown to dark brown with row of 2–4 paler spots between inner rays near the fin base, and large paler area distally on fin (this pale area absent in the juvenile 82.5 mm SL). In juveniles 96–103 mm SL pelvic fins dark in distal half and near fin base, with pigmentation weaker near base; remainder of fin pale, sometimes with a few dots.

Dorsal fin of juveniles 33–82.5 mm SL pale with dark patch near base of first few rays and a dark spot on upper part. Posterior edge of fin pale. In a juvenile 103 mm SL, the fin pale with dark upper edge.

Anal fin of juveniles 33–82.5 mm SL transparent with small aggregation of dots or with spot on posterior part near ends of rays. In fish 96–103 mm SL fin transparent.

Caudal fin in fish 33–82.5 mm SL pale with pigmented base and brown pigmentation along rays of lower lobe (except for the uppermost rays), usually forming two bands here. Upper lobe with only solitary dots centrally, and only largest fish with pigment on lobe tip. Fish 96–103 mm SL without bands on caudal fin.

Chin barbels of juveniles 43–52.5 mm, if present, are pale proximally and covered with melanophores of varying density in their distal (wider) part.

Intraspecific variation. Cheilopogon (Ptenichthys) sp.1 may be a mixture of two species, because specimens captured from Shark Bay to 32°S differ somewhat from fish captured in more northern waters in having a more elongate body with a shorter head, as well as differing in values of lA, Dc/c, lP, lP 1, Str (see Table 8). It is not known if these differences are the result of intraspecific variation or if we are dealing with two different species, and a taxonomic revision of the subgenus Ptenichthys is required.

Comparative remarks. Cheilopogon (Ptenichthys) sp.1 (like Cheilopogon sp.2, see below) differs from all other species previously misidentified as C. hexazona in having longer pelvic fins ( Fig. 18 ) situated closer to the head (aV less than 55% SL) and a higher number of vertebrae (45 or more), as well as in pigmentation of pectoral and pelvic fins.

Cheilopogon (Ptenichthys) sp.1 is probably a juvenile stage of a species (or species) of the subgenus Ptenichthys , which occurs in the waters off Western Australia. Its similarity to Cheilopogon olgae Parin in meristic characters and distribution (see Parin, 2009) suggests that it may be a juvenile stage of this species, or a closelyrelated, undescribed species. However the juveniles described by Parin (2009, fig. 2) as Ch. olgae differ from juveniles of Cheilopogon sp. 1 in the structure of chin barbels.

Distribution. Cheilopogon (Ptenichthys) sp.1 is distributed in neritic waters of the western and north-western coasts of Australia ( Fig. 3 ).

Figures

FIGURE 3. Distribution of flying fishes Cheilopogon formosus formosus (□), Ch. formosus pseudospilopterus (Δ), Ch. formosus andamanicus (◊), Ch. marisrubri (○), Cheilopogon (Ptenichthys) sp.1 (x) and Cheilopogon (Ptenichthys) sp. 2 (+). Filled symbols indicate capture location for fishes ≤100 mm SL, open symbols indicate capture location for fishes>100 mm SL.

FIGURE 15. Flying fishes Cheilopogon (Ptenichthys) sp.1 and sp.2. (A)—Cheilopogon sp.1, 48 mm SL, WAM P.6208-001, 28°45’S 113°50’E (drawing by T.N. Belyanina); (B)—Cheilopogon sp.2, 24.7 mm SL, ~19°S ~147°E (after Belyanina, 1993).

FIGURE 16. Flying fish Cheilopogon (Ptenichthys) sp.1. (A)—43 mm SL, FRSKU 114540, 20°00’S 117°04’E; (B)—48.5 mm SL, FRSKU 114540, same place; (C)—65 mm SL, FRSKU 114540, same place; (D)—82.5 mm SL, FRSKU 113559, 20°00’S 116°59’E.

FIGURE 17. Pectoral (left) and pelvic (right) fins in flying fishes Cheilopogon (Ptenichthys) sp.1 (A–B) and Cheilopogon (Ptenichthys) sp.2 (C–D). (A)—48.5 mm SL, FRSKU 114540, 20°00’S 117°04’E; (B)—65 mm SL, FRSKU 114540, same place; (C)—48 mm SL, AMS I.19461-060, 14°40’S 145°28’E; (D)—67 mm SL, AMS I.23902-001, 32°28’S 152°05’E.

FIGURE 18. Size variation of morphometric characters in flying fishes Cypselurus bosha (□), C. olpar (○), Cheilopogon formosus (x), Ch. marisrubri (+), Ch. katherinae (◊), Cheilopogon sp. 1 (∆) and Cheilopogon sp. 2 (▲). (A)—length of pectoral fin divided by length of pelvic fin (index lP/lV), (B)—length of pelvic fin (lV), (C)—greatest head depth (Hc).