Ventrifossa macroptera Okamura, 1982

Nakayama, Naohide, 2020, Grenadiers (Teleostei: Gadiformes: Macrouridae) of Japan and adjacent waters, a taxonomic monograph, Megataxa 3 (1), pp. 1-383 : 298-301

Ventrifossa macroptera Okamura, 1982

[Japanese name: Parao-sokodara]

( Figs. 206–207 ; Appendix 3-12F)

Ventrifossa macroptera Okamura, 1982:149 , fig. 92, table 15 (original description; holotype: BSKU 32185, from Kyushu-Palau Ridge, 27º55.1ʹN, 134º44.8ʹE, in 685–710 m; 52 paratypes collected with holotype; new Japanese name: “Parao-sokodara”); Okamura 1984b:93, pl. 81, fig. A (compiled); Okamura 1988:93, pl. 81, fig. A (compiled); Iwamoto 1990:303, fig. 682 (synopsis); Nakabo 1993:358 (in key; Japan); Okamura 1997:128, fig. 12 (compiled); Nakabo 2000:422 (in key; Japan); Nakabo 2002:422 (in key; Japan); Chiou et al. 2004a:48, fig. 21, table 1 (brief description; 2 spec. from Dong-gang; first record from Taiwan); Shao et al. 2008b: table 2 (89 spec. listed from northeastern and southwestern Taiwan, and South China Sea); Nakabo & Kai 2013:498 (in key; Japan); Iwamoto et al. 2015:111 (brief description; 122 spec. from northeastern and southwestern Taiwan, South China Sea, and Kyushu-Palau Ridge); Motomura 2020:39 (listed; Japan).

Ventrifossa atherodon (not Gilbert & Cramer 1897): Chiou et al. 2004a:46, fig. 18, table 1 (brief description; 1 spec. from Daxi; first record from Taiwan) [fide Iwamoto et al. (2015)].

Diagnosis. Second spinous ray of first dorsal fin smooth along its leading edge; first dorsal fin blackish; anal fin darker anteriorly; prominent black spot present on front of premaxillary ascending process; oral cavity pale; median rostral ridge lacking narrow blackish streak; leading edges of snout and suborbital shelves prominently marked with black; body dusky brown, with much darker abdomen; scale pockets narrowly outlined in dark; snout low, slightly protruding beyond upper jaw, preoral length 13–17% HL; no scute-like scale at snout tip; body scales covered with short, moderately erect, needle-like spinules in quincunx order; spinules on scales along second dorsal-fin base not enlarged; body scales moderately small, transverse scale rows below midbase of first dorsal fin 5.5–8.5, below second dorsal-fin origin 7–10; longitudinal scales 50–58; area of spinuleless scales posterior to first dorsal-fin base moderately developed; outer series of premaxillary teeth distinctly enlarged; mandibular teeth arranged in 2 irregular rows, with inner row slightly enlarged; suborbital shelf constricted anteriorly; inner gill rakers on first arch 17–19, outer gill rakers on second arch 16–18; orbit in moderate size, greatest diameter 28–33% HL; upper-jaw length 47–51% HL; interorbital space broad, width 29– 33% HL; chin barbel moderately long, length 14–26% HL; pectoral fin well developed, length 69–81% HL.

Material examined. 54 specimens. Holotype of Ventrifossa macroptera: BSKU 32185 (65.8 mm HL, 338+ mm TL), Kyushu-Palau Ridge , Japan, 27.9178ºN, 134.7460ºE, 685–710 m, F/ V Yuryo-maru, No. 8, tr. T8, bottom trawl, coll. O. Okamura et al., 19 Dec. 1979 . Paratypes of V. macroptera : * BSKU 29429 (1, 68.3 mm HL, 353+ mm TL) , BSKU 32153 (1, 67.5 mm HL, 360 mm TL) , * BSKU 32154 (1, 65.9 mm HL, 353+ mm TL) , * BSKU 32155 (1, 67.2 mm HL, 349+ mm TL) , * BSKU 32156 (1, 67.1 mm HL, 279+ mm TL) , * BSKU 32157 (1, 69.9 mm HL, 307+ mm TL) , * BSKU 32158 (1, 67.2 mm HL, 348+ mm TL) , * BSKU 32159 (1, 68.9 mm HL, 394+ mm TL) , BSKU 32160 (1, 70.2 mm HL, 328 mm TL) , BSKU 32161 (1, 66.0 mm HL, 341 mm TL) , BSKU 32162 (1, 61.7 mm HL, 322 mm TL) , * BSKU 32163 (1, 65.2 mm HL, 257+ mm TL) , BSKU 32164 (1, 59.9 mm HL, 316 mm TL) , * BSKU 32165 (1, 32.2 mm HL, 348+ mm TL) , * BSKU 32166 (1, 69.4 mm HL, 378+ mm TL) , BSKU 32167 (1, 73.5 mm HL, 401+ mm TL) , * BSKU 32168 (1, 71.0 mm HL, 391+ mm TL) , BSKU 32169 (1, 68.9 mm HL, 367 mm TL) , * BSKU 32170 (1, 71.8 mm HL, 331+ mm TL) , * BSKU 32171 (1, 71.0 mm HL, 405+ mm TL) , BSKU 32172 (1, 70.0 mm HL, 362 mm TL), BSKU 32173 (1, 70.7 mm HL, 403 mm TL) , * BSKU 32174 (1, 67.4 mm HL, 361+ mm TL) , BSKU 32175 (1, 64.5 mm HL, 326 mm TL) , * BSKU 32176 (1, 60.7 mm HL, 284+ mm TL) , * BSKU 32177 (1, 66.1 mm HL, 370+ mm TL) , * BSKU 32178 (1, 71.0 mm HL, 367+ mm TL) , BSKU 32179 (1, 66.4 mm HL, 330 mm TL) , BSKU 32180 (1, 61.1 mm HL, 323 mm TL) , BSKU 32181 (1, 63.6 mm HL, 327 mm TL) , BSKU 32182 (1, 57.4 mm HL, 308 mm TL) , * BSKU 32183 (1, 66.5 mm HL, 368+ mm TL) , * BSKU 32184 (1, 67.7 mm HL, 362+ mm TL) , * BSKU 32186 (1, 70.4 mm HL, 373+ mm TL) , BSKU 32187 (1, 63.7 mm HL, 326 mm TL) , BSKU 32188 (1, 59.7 mm HL, 270 mm TL) , * BSKU 32189 (1, 62.0 mm HL, 369+ mm TL) , BSKU 32192 (1, 56.9 mm HL, 290 mm TL) , * BSKU 32193 (1, 58.2 mm HL, 316+ mm TL) , BSKU 32194 (1, 51.4 mm HL, 262 mm TL) , BSKU 32195 (1, 48.4 mm HL, 276 mm TL) , BSKU 32196 (1, 50.8 mm HL, 266 mm TL) , * BSKU 32197 (1, 47.9 mm HL, 256+ mm TL) , BSKU 32198 (1, 47.6 mm HL, 263 mm TL) , * BSKU 32199 (1, 46.1 mm HL, 249+ mm TL) , BSKU 32200 (1, 54.4 mm HL, 271 mm TL), collected with holotype ; BSKU 30467 (1, 61.9 mm HL, 336 mm TL) , * BSKU 30468 (1, 63.5 mm HL, 345+ mm TL) , * BSKU 30469 (1, 62.4 mm HL, 335+ mm TL), Kyushu-Palau Ridge , 27.9000ºN, 134.6667ºE, 697–700 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, sta. T11, bottom trawl, coll. Y. Kobayashi et al., 18 Dec. 1979 ; * BSKU 30432 (1, 64.7 mm HL, 303+ mm TL) , * BSKU 30435 (1, 69.2 mm HL, 362+ mm TL) , BSKU 30436 (1, 69.8 mm HL, 372 mm TL), Kyushu-Palau Ridge , 26.7500ºN, 135.3167ºE, 336 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, sta. T8, bottom trawl, coll. Y. Kobayashi et al., 17 Dec. 1979 . Non-types : Japan : BSKU 30470 (1, 73.2 mm HL, 383+ mm TL), Kyushu-Palau Ridge , 27.9000ºN, 134.6667ºE, 697–700 m, F/ Vs Shinsei-maru, No. 53 and Kyoyo-maru, No. 2, sta. T11, bottom trawl, coll. Y. Kobayashi et al., 18 Dec. 1979 .

Counts and measurements. Based on 26 specimens (47.6–73.7 mm HL, 262+–403+ mm TL). Counts: first dorsal-fin rays II,9–11; pectoral-fin rays i20–i25; pelvicfin rays 9–10; gill rakers on first arch (outer/inner) 11– 16/17–19, on second arch 16–18/16–19; longitudinal scales 50–58; transverse scale rows below first dorsal-fin origin 8.5–10.5, below first dorsal-fin midbase 5.5–8.5, below second dorsal-fin origin 7–10, above anal-fin origin 32–39.5.

The following measurements are in % of HL, followed by those in % of PRL in parentheses: snout length 27–31 (36–43); orbit diameter 28–33 (37–44); postorbital length 44–49 (59–65); postrostral length 72–77; orbit–preopercle distance 46–50 (59–67); suborbital width 13–16 (18–21); upper-jaw length 47–51 (62–68); length of rictus 40–44 (53–58); length of premaxillary tooth band 36–42 (48– 54); preoral length 13–17 (17–22); distance between tip and lateral angle of snout 19–22 (24–29); snout width 29– 33 (37–44); internasal width 23–28 (31–37); interorbital width 29–33 (38–46); occipital width 15–18 (20–23); body width over pectoral-fin bases 45–59 (61–77); body depth at first dorsal-fin origin 80–99 (105–132); body depth at anal-fin origin 76–91 (99–121); prepelvic length 105–117 (140–156); preanus length 113–126 (147–168); preanal length 130–150 (172–200); isthmus–pelvic distance 40–51 (54–69); isthmus–anus distance 51–62 (69–82); isthmusanal distance 67–88 (90–117); pelvic–anal distance 27–41 (36–54); anus–anal distance 15–29 (21–38); pelvic-fin length 41–54 (57–72); pectoral-fin length 69–81 (92– 107); predorsal length 104–112 (138–152); height of first dorsal fin 67–78 (88–104); length of first dorsal-fin base 24–32 (32–43); interdorsal length 42–71 (57–94); length of gill slit 28–32 (38–42); length of posterior nostril 3–6 (4–8); barbel length 14–26 (18–34).

Size. To about 40 cm TL ( BSKU 32173 , paratype, 403+ mm TL, Kyushu-Palau Ridge , Japan) .

Distribution. So far known from the Kyushu-Palau Ridge and the East and South China Seas off Taiwan at depths of 227–1320 m ( Chiou et al. 2004a, Shao et al. 2008a, 2008b; Iwamoto et al. 2015; this study; Appendix 3-12F). Common in the Kyushu-Palau Ridge.

Remarks. For a full description see Okamura (1982). Ventrifossa macroptera was originally described from 53 specimens collected from the Kyushu-Palau Ridge ( Figs. 206–207 ). In addition to the type locality, it is also known from Taiwan ( Chiou et al. 2004a; Shao et al. 2008a, 2008b; Iwamoto et al. 2015). Chiou et al. (2004a) included Hawaii in the distribution of V. macroptera , but no specimens of this species have been collected from that area. A previous record of V. atherodon ( Gilbert & Cramer, 1897) from Taiwan ( Chiou et al. 2004a) represents a misidentification of V. macroptera (see Iwamoto et al. 2015:112).

Relationships and comparisons. Ventrifossa macroptera is the only species of the subgenus Atherodus Gilbert & Hubbs, 1920 known from Japan. It readily differs from other Japanese congeners in having the second spinous ray of the first dorsal fin smooth along its leading edge (vs. finely serrated), the outer series of the premaxillary tooth band is distinctly enlarged (vs. only slightly enlarged), and the mandibular teeth arranged in 2 irregular rows (vs. tapered band).

In addition to V. macroptera , Atherodus includes the following three species: V. atherodon distributed in the Hawaiian Archipelago and New Caledonian region; V. macrodon Sazonov & Iwamoto, 1992 confined to the Sala y Gomez Ridge in the southeastern Pacific; and V. sazonovi Iwamoto&Williams, 1999 known from Australia to Taiwan. Ventrifossa macroptera is readily separated from the other species of Atherodus by having a longer pectoral fin (69–81% HL vs. 51–68% in V. atherodon , 49–61% in V. macrodon , and 42–65% in V. sazonovi ). This species is further distinguished from V. macrodon and V. sazonovi by having a wider interorbital space (29– 33% HL vs. 20–24% and 22–28% in V. macrodon and V. sazonovi respectively) and a longer preoral (13–17% HL vs. 7–11% and 6–12% respectively). In addition, it differs notably from V. sazonovi in lacking enlarged spinules on the scales below the anterior portion of the second dorsal-fin base. Ventrifossa macroptera also differs from the two V. atherodon specimens examined (FMNH 2552 and FMNH 55979, 40.3–63.7 mm HL, 171+–307+ mm TL, from Hawaii) in having lower counts of outer gill rakers on the second arch (16–18 vs. 19) and many morphometric characters, including the snout length (27– 31% HL vs. 25–26%), orbit diameter (28–33% HL vs. 34–35%), orbit–preopercle distance (46–50% HL vs. 42– 43%), suborbital width (13–16% HL vs. 10–11%), preoral length (13–17% HL vs. 7–10%), snout width (29–33% HL vs. 24–26%), internasal width (23–28% HL vs. 19– 20%), and interorbital width (29–33% HL vs. 22–23%). The body color of V. macroptera is uniformly dark ( Figs. 206–207 ), whereas the V. atherodon specimens examined have prominent silvery reflections on the sides of the body. [Data for V. atherodon , V. macrodon , and V. sazonovi are based on Sazonov & Iwamoto (1992), Iwamoto & Merrett (1997), Iwamoto & Williams (1999), and this study.]

Figures

FIGURE 206. Fresh specimen of Ventrifossa macroptera. BSKU 29429, paratype, 68.3 mm HL, 353+ mm TL, Kyushu-Palau Ridge, Pacific, 685–710 m depth. Lateral view. [Photo: BSKU]

FIGURE 207. Holotype of Ventrifossa macroptera. BSKU 32185, 65.8 mm HL, 338+ mm TL, Kyushu-Palau Ridge, Pacific, 685–710 m depth. (A) Lateral view; (B) dorsal and (C) ventral views of the head and trunk. Preserved condition. [Photos: N. Nakayama]