ソコダラ科　Macrouridae                                                    Grenadiers, Rattails

 

8 クロボウズダラ

Odontomacrurus murrayi Norman, 1939                   Largefang Whiptail, Roundhead Grenadier

 

Specimens examined: 2 (SNFR 16598, 16599; 79.4–80.7 mm HL, 580–620+ mm TL), 298–430 m depth (mid-water trawl).

Counts: D I–II, 7–8; P₁ 10; P₂ 7–8; first GR (outer/inner) 0+8/1–2+9; 2nd GR (outer/inner) 0+10/1+8; scale rows below first dorsal-fin origin 11; scale rows below midpoint of interdorsal space 9 branchiostegal rays 6. Measurements (all expressed as % HL): body depth at anal-fin origin 117.1; snout length 31.7–33.1; orbit diameter 17.0–17.1; interorbital width 38.4–40.5; suborbital length 24.1–25.4; postorbital length 53.7–54.9; upper-jaw length 70.9–72.3; pectoral-fin length 37.4; pelvic-fin length 35.6; 1st dorsal-fin base length 26.2–30.1; predorsal-fin length 97.9; pre-anus length 113.9; preanal-fin length 131.0. interdorsal distance 74.6–100.8.

 

計数形質：背鰭1–2擬棘，7–8軟条；胸鰭10軟条；腹鰭7–8軟条；第1鰓弓の鰓耙数（外側/内側）0+8/1–2+9；第2鰓弓の鰓耙数（外側/内側）0+10/1+8；横列鱗数（第1背鰭起部下）11；横列鱗数（両背鰭間隔の中間点下）9；鰓条骨数 6．計測形質（全て% HL）：体高（臀鰭始部上）117.1; 吻長 31.7–33.1；眼窩径 17.0–17.1; 両眼間隔幅 38.4–40.5; 眼下長24.1–25.4; 眼後長53.7–54.9；上顎長 70.9–72.3; 胸鰭長37.4; 腹鰭長 35.6; 第１背鰭基底長 26.2–30.1; 背鰭前長 97.9; 肛門前長 113.9; 臀鰭前長 131.0.

特　徴　頭部，体幹部および尾部前方では高く，卵形でよく側扁する．尾部は後部で細長く，ヒモ状．吻は短く丸い．眼は小さい．口は大きい．下顎は短く，閉口時に上顎内に収まる．両顎に1列の犬歯状歯が並び，下顎歯は上顎歯より大きく，後部で疎ら．鋤骨と口蓋骨に歯がない．下顎先端にヒゲがない．鰓耙は針状．背鰭は2基．第1背鰭始部は前鰓蓋骨後端の直上で，両背鰭間隔は広い．背鰭第1棘は痕跡的または消失．背鰭第2棘は伸長し，前縁は円滑．臀鰭始部は腹鰭に接近する．腹鰭基底間に発光器を備える無鱗域を１個もつ．肛門は腹鰭始部間と臀鰭始部の中間に位置する．体は一様に棘状鱗で覆われるが，発光器と肛門周辺は無鱗．鱗は小さく，10本前後の長く，直立した棘を備える．側線は短く，体の前部背縁近くにあり，溝状．体は黒色から暗褐色で，皮膚はやや青味を帯びる．最大で約全長62cm ．

分　布　三大洋の熱帯から温帯水域．既知の採集水深は 0–900 m（海底水深は2000 m以深）（Iwamoto and Graham, 2001; Nakayama et al., 2015）.

備　考　本種は，鰓条骨数が6，口が頭部前端に開くこと，下顎先端にヒゲがないことで， 南大洋産のキバソコダラCynomacrurus pirieri Dollo, 1909を除くすべてのソコダラ亜科魚類と明瞭に異なる(Iwamoto, 1990)．キバソコダラとは次の形質により識別できる：肛門が臀鰭起部から離れる（vs. 臀鰭起部直前），上顎に犬歯がない（vs. ある），発光器がある（vs. ない），胸鰭鰭条数が8–11（vs. 15–17）(Iwamoto, 1990; Iwamoto and Graham, 2001)．日本の東北太平洋岸沖で本種の1標本が採集され，属と種の標準和名が提唱された（Nakayama et al., 2015）．

（遠藤）

 

Description  Head, trunk, and anterior caudal area deep, oval, and compressed. Tail tapering posteriorly, becoming slender and long. Snout short, rounded. Eye small. Mouth large; lower jaw short, settled in upper jaw when closed. Single row of canine-like teeth on both jaws; teeth larger on lower jaw; sparsely arranged posteriorly. No teeth on vomer and palatine. No chin barbel. Gill rakers needle-like. Two dorsal fins; first dorsal-fin origin located above posterior margin of preopercle; interdorsal space wide. First dorsal spine vestigial or absent; second long with smooth leading edge. Anal-fin origin very close to pelvic-fin base. Light organ with a dermal window present between pelvic-fin bases. Anus midway between pelvic-fin insertion and anal-fin origin. Body fully covered with spinoid scales except light organ and periproct. Scales small, with ca. 10 erected spines. Lateral line short, located at antero-dorsal part of body, grooved. Scaled body black to blackish brown with bluish skin. Reaches about 62 cm TL.

Distribution  Atlantic, Indian, and Pacific oceans from tropical to temperate waters. Capture depths were 0–900 m (over bottom depths of more than 2000 m) (Iwamoto and Graham, 2001; Nakayama et al., 2015).

Remarks  This monotypic genus clearly differs from all other macrourine genera except the monotypic Cynomacrurus from the Southern Ocean by having 6 branchiostegal rays, terminal mouth, and no chin barbel (Iwamoto, 1990). This species can be distinguished from Cynomacrurus piriei Dollo, 1909 in having the anus well anterior to the anal fin (vs. just before anal fin), no fangs on the upper jaw (vs. present), a light organ present (vs. absent), and 8–11 pectoral-fin rays (vs. 15–17) (Iwamoto, 1990; Iwamoto and Graham, 2001).

 (H. Endo)