Ateleopus edentatus, Kaga, 2016

Kaga, Tatsuya, 2016, A new jellynose, Ateleopus edentatus, from the western Pacific Ocean (Teleostei: Ateleopodiformes: Ateleopodidae), Zootaxa 4083 (4) : -

Ateleopus edentatus sp. nov.

[Japanese name: Shiroguchi-shachiburi] ( Figs. 1–2 , 4; Tables 1–2)

Ateleopus sp. b: Mochizuki 1982: 117, pl. 76 (description, Japan)

Ateleopus sp.: Mochizuki 1984: 115, pl. 100 (description, Japan); Mochizuki 2001: 109, fig. 18 (description, Japan); Aizawa, 2002: 347 (key, Japan); Aizawa & Doiuchi 2013: 410 (key, Japan)

Holotype. FUMT 20696 (154 mm PAL; Fig. 1 ), Kyushu-Palau Ridge, 26º45’N, 135º23’E, 350 m depth, bottom trawler.

Paratypes (all from Kyushu-Palau Ridge). 11 specimens (94–269 mm PAL): BSKU 26150 (204 mm PAL), 26º45.6’N, 135º19.0’E, 344 m, bottom trawler; BSKU 31722–31723 (2 specimens, 126–144 mm PAL), 26º45.01’N, 135º19.0’E, 322–345 m, bottom trawler; FUMT 20694–20695, 20697 (3, 121– 248 mm PAL), 26º45’N, 135º23’E, 320 m, bottom trawler; HUMZ 80182–80184, 80343, 80444 ( Figs. 2 and 4) (5, 94– 269 mm PAL), 26º46.9’N, 135º20.4’E, 360 m, bottom trawler.

Diagnosis. A species of Ateleopus distinguished from all congeners by the absence of teeth in the upper jaws. It is also distinguished from A. indicus by having 94–130 anal+caudal-fin rays (vs. 76–82 in A. indicus ); 11–13 gill rakers (vs. 7–8); 26–28+81–107=109–135 vertebrae (vs. 22–24+75–80=97–103).

Description. Counts and measurements of the holotype and paratypes of Ateleopus edentatus are given in Table 1. In this description, data of paratypes are shown in parentheses when variation is recognized between holotype and paratypes.

Body elongate, compressed; body depth at dorsal-fin origin 3.3 (2.3–3.4) in PAL; tail long, length 2.1 (1.7–2.3) times PAL, tapering to caudal fin, completely enveloped in a soft gelatinous tissue; scales absent. Head large, length 2.0 (1.5–2.1) in PAL, slightly compressed, covered with thick gelatinous tissue forming gelatinous snout. Anterior nostril with a short tube; posterior nostril large without a tube, situated just in front of upper half of eye. Eye small, diameter 5.7 (5.2–9.8) in HL. Interorbital space wide, with a deep longitudinal groove. A large obtuse spine projecting laterally from posterior margin of eye. Two small obtuse spines between large obtuse spine and gill opening. Mouth inferior, protractile, rather small, upper jaw length 2.6 (2.5–3.3) times in HL. Posterior end of maxilla extending to posterior end of orbit. Both lips thick, rather thick in specimens <126 mm PAL, very thick in specimens> 248 mm PAL, with many wrinkles and tiny papillae. Both jaws, palatine, vomer, and tongue toothless. Symphysis of lower jaw convex in front. Preopercular margin adnate, not free; gill opening wide; gill membranes separate, free from isthmus. Upper margin of opercle usually acute, protruded posteriorly. Uppermost gill raker of first gill arch straddling angle of arch. Gill rakers on first gill arch flattened, except for several stumpy rakers on hypobranchial portion; gill rakers on other arches all stumpy. All tips of gill rakers bluntly pointed, the edge very weakly spinulose. No pseudobranchiae. Branchiostegal rays seven. Dorsal-fin origin slightly behind base of pectoral fin; dorsal-fin base short, length 3.8 (2.6–4.0) in HL. Dorsal fin long, the longest rays, approximately equal to pectoral-fin length. Pectoral fin long, length 2.0 (1.7–2.2) in PAL, the tip reaching anus (just anterior to anus, to beyond anal-fin origin). Pelvic fin jugular, long, the tip tapered (tapered or flattened) and extending to anterior onethird of pectoral fin (just beyond base of pectoral to midway along pectoral fin). Pelvic fin appearing like one long ray, but actually consisting of two minute rudimentary rays attached to front base of this long third ray; some vestigial rays in cutaneous membrane on the medial side of the base. Precise count of pelvic-fin rays difficult, especially large specimens> ca. 170 mm PAL, because of rudimentary anterior two rays and cutaneous membrane becoming very small. Anal-fin base long, continuous with caudal fin. Anus just in front of anal-fin origin.

Color in preserved specimens. Head and body brownish; both lips light brownish; dorsal and pectoral fins black; pelvic fin white, base of pelvic fin brownish; anal and caudal fins brownish.

Etymology. The species name “ edentatus ” is derived from the Latin meaning “no teeth”.

Distribution. Kyushu-Palau Ridge in the western Pacific Ocean. Depth range from 320 to 360 m, on sandymuddy bottoms ( Mochizuki 1982, 1984, 2001; Aizawa 2002; Aizawa & Doiuchi 2013; this study).

Comparisons. The ateleopodid fishes comprise four genera, Ateleopus Temminck & Schlegel 1846 , Guentherus Osório 1917 , Ijimaia Sauter 1905 , and Parateleopus Smith & Radcliffe in Radcliffe 1912 . The new species is classified in Ateleopus based on their having 10–12 dorsal-fin rays (vs. three in Parateleopus ), long pelvic-fin rays extending beyond origin of pectoral fin (vs. short pelvic-fin ray, scarcely reaching upper origin of pectoral fin in Ijimaia ), and pelvic-fin rays consisting of one elongated ray and two minute rudimentary rays attached to front base of long ray, and some vestigial rays in cutaneous membrane on the medial side of the base (vs. three free rays followed by normal rays in Guentherus ) ( Howell Rivero 1935; Smith 1986; Senou et al. 2008; Kaga et al. 2015).

Three species are known as valid in the genus Ateleopus ( Kaga et al. 2015) : A. japonicus Bleeker 1853 , A. indicus Alcock 1891 , and A. natalensis Regan 1921 . Ateleopus edentatus sp. nov. is easily distinguishable from A. indicus by the following features: anal+caudal-fin rays 94–130 (vs. 76–82 in A. indicus ); gill rakers 0+11–13=11– 13 (vs. 0+7–8=7–8); vertebrae 26–28+81–107=109–135 (vs. 22–24+75–80=97–103); upper-jaw teeth absent (vs. tooth band present). The new species is not easily distinguished from A. japonicus and A. natalensis by their counts and measurements, but is clearly distinguishable by the presence or absence of teeth on the upper jaw. Ateleopus edentatus sp. nov. has no teeth on the upper jaw ( Fig. 2 ), while A. japonicus , A. natalensis , and A. indicus have many teeth in a band. The upper-jaw teeth are very stable forming a tooth band ( Fig. 3 ) in all examined specimens of A. japonicus , A. natalensis , and A. indicus and this character is considered to be taxonomically reliable; in contrast, the lower-jaw teeth are very deciduous and unreliable as a specific diagnostic character in the genus Ateleopus ( Kaga et al. 2015) .

Diagnostic characters of Ateleopus edentatus sp. nov. and three other species of Ateleopus are summarized in Table 2.

Remarks. The tail lengths of three large specimens (216, 248, and 269 mm PAL) of Ateleopus edentatus were much shorter than those of other specimens of the species. The tail length of one of the three large paratypes, HUMZ 80444, 269 mm PAL (Fig. 4) is the shortest at 165.8 % PAL. In contrast, the holotype, FUMT 20696, 154 mm PAL, has a long tail at 207.5 % PAL ( Fig. 1 ), and other paratype, FUMT 20694, 150 mm PAL, has the longest tail at 228.3 % PAL ( Table 1). For the photographs of Ateleopus sp. in Mochizuki (1982: pl. 76, 1984: pl. 100, 2001: 109; fig. 18) and the illustration of the Ateleopus sp. in Aizawa (2002: 348) and Aizawa & Doiuchi (2013: 411), those authors used only the short-tailed specimen. Therefore, at first sight the short tail might be mistaken for a specific diagnostic character by the readers.

FIGURE 4. Paratype of Ateleopus edentatus sp. nov., HUMZ 80444, 269 mm PAL, 670+ mm SL, from Kyushu-Palau Ridge, Japan.

However, these large specimens also had smaller numbers of caudal vertebrae (81–89 vs. 102–107 in the longer-tailed specimens) and anal+caudal-fin rays (94–109 vs. 121–130). The caudal portion of the vertebrae (examined in radiographs) in the three specimens are not tapered (vs. tapered in the longer-tailed specimens). The hypurals could not be observed well in all specimens of A. edentatus , because they are for the most part cartilaginous in Ateleopus ( Fujita 1990: fig. 172). In the specimen 216 mm PAL, the last element of vertebrae is triangular, but it is thick and also articulates with a thick vertebra (vs. slender ural vertebrae articulate with tapered vertebrae in longer-tailed specimens; an indication that the element in the former is not the ural vertebra). In the specimens 248 and 269 mm PAL, several posteriormost caudal vertebrae were deformed, and their sizes were irregular, and the ural vertebra were not observed. Hence it is obvious that the shorter tails are a result of loss of the posterior part of the tail, and all three of these larger specimens of A. edentatus had damaged tails that had partially regrown.

The tip of the pelvic fin of A. edentatus is tapered or flattened (not swollen), although it was swollen and slightly flattened in A. japonicus ( Kaga et al. 2015: fig. 3B). However, the tip of the pelvic fin of A. edentatus might be damaged or shrunken by dehydration. The specimens of A. edentatus probably had been frozen for a while after capture by bottom trawler. The process of thawing the frozen specimens and soaking them in alcohol after fixation in formalin may have caused damage to the soft tissue of the pelvic-fin tip. Therefore, I considered that the shape of the pelvic-fin tip of A. edentatus should not be used as a specific diagnostic character in this study.

Figures

FIGURE 1. Holotype of Ateleopus edentatus sp. nov. (a, b), FUMT 20696, 154 mm PAL, 440 mm SL, from Kyushu-Palau Ridge, Japan. Bar 50 mm.

FIGURE 2. Upper jaw without teeth in paratype of Ateleopus edentatus sp. nov., HUMZ 80444, 269 mm PAL.

FIGURE 3. Upper-jaw tooth band in one of the syntypes of Ateleopus natalensis Regan 1921, BMNH 1921.3.1.7 – 8, 515 mm SL. Photographed by James Maclaine.