ヤセムツ科　Epigonidae                         Deepwater Cardinalfishes

 

26 オオヤセムツ

Epigonus telescopus (Risso, 1810)  Black Cardinalfish

 

Specimens examined: 2 (SNFR 16711, 16712; 635–706 mm SL), 661–690 m depth.

Counts: D VII-I-I, 10; A II, 9; P₁ 18; P₂ I, 5; GR 6+17=23; LLS 46–48+2–4 (caudal fin); scales above lateral line 3; scales below lateral line 11–12; V 11+14=25. Measurements: head length 32.4–35.3% SL; body depth 25.1–25.5% SL; eye diameter 27.2–28.0% HL; interorbital width 31.0–34.6% HL; snout length 25.3–29.4% HL; upper-jaw length 42.4–43.6% HL; lower-jaw length 46.6–50.6% HL; caudal-peduncle length 21.7–22.6% SL; caudal-peduncle depth 7.6–7.8% SL; pectoral-fin length 16.6–16.8% SL; pelvic-fin length 13.3–14.4% SL; spine length of second dorsal-fin 4.6% SL; second anal-fin spine length 5.1–5.4% SL; pelvic-fin spine length 7.5–7.9% SL; first dorsal-fin base length 11.7–12.4% SL; second dorsal-fin base length 11.1–11.5% SL; anal-fin base length 8.3–9.2% SL.

 

計数形質：背鰭7棘-1棘-1棘，10軟条；臀鰭2棘，9軟条；胸鰭18；腹鰭1棘，5軟条；鰓耙数6+17=23；側線鱗数 46–48+2–4（尾鰭）；側線上方鱗数3；側線下方鱗数11–12；脊椎骨数11 + 14 = 25．計測形質：頭長32.4–35.3% SL；体高25.1–25.5% SL；眼径27.2–28.0% HL；両眼間隔31.0–34.6% HL；吻長25.3–29.4% HL；上顎長42.4–43.6% HL；下顎長46.6–50.6% HL；尾柄長21.7–22.6% SL；尾柄高7.6–7.8% SL；胸鰭長16.6–16.8% SL；腹鰭長13.3–14.4% SL；第2背鰭の棘長4.6% SL；第2臀鰭棘長5.1–5.4% SL；腹鰭棘長7.5–7.9% SL；第1背鰭基底長11.7–12.4% SL；第2背鰭基底長11.1–11.5% SL；臀鰭基底長8.3–9.2% SL．

特　徴　体は側扁し，体高は体長の約1/4．頭部は大きく幅広く，頭長は体長の約1/3．吻は丸く短い．眼は円形で大きく，両眼間隔は眼径より広い．主鰓蓋骨に棘はない．口は大きい．絨毛状歯帯が両顎，鋤骨および口蓋骨にあるが，舌上に歯はない．背鰭は2基で離れ，その間に独立した短い1棘がある（大型個体では退縮してやや不明瞭）．臀鰭始部は第2背鰭始部よりも後方にある．胸鰭および腹鰭は短く，肛門に達しない．肛門は第2背鰭始部の直下にある．尾鰭の後縁は深く湾入する．鱗は弱い櫛鱗で剥がれやすい．側線は1本で明瞭．体と各鰭は黒茶色．頭部も黒茶色で青紫に反射し，口内は黒色．

分　布　大西洋東部，地中海，大西洋北西部，インド洋，オーストラリア，ニュージーランド（Mayer, 1974; Abramov, 1992）．

備　考　本種は，コハクヤセムツE. angustifrons Abramov and Manilo, 1987に似るが，鰓耙数が23–26（vs. コハクヤセムツ33–36），体高が高く体長の約1/4（vs. 約1/5），また体長は70 cmに達する（vs. コハクヤセムツは40 cm以下）ことで異なる．本海域に出現する他の同属種からは，鰓耙数（23–26 vs. ハゲヤセムツE. denticulatus Dieuzeide, 1950は28–34），側線鱗数（46–50 vs. E. exodon Okamoto and Motomura. 2012は35–37），および鰓蓋骨棘をもたない［vs. マルヤセムツE. robustus (Barnard, 1927)はもつ］ことで異なる（Okamoto 2012; Okamoto and Motomura 2012, 2013）．背鰭の独立棘は成長に伴い小さくなり，大型個体では痕跡的になる．本種は，ヤセムツ属では最大の種（最大全長85 cm）で，食用に利用される．

（岡本）

 

Description  Body laterally compressed, body depth about 1/4 of SL. Head large and rather wide, its length about 1/3 of SL. Snout round, short. Eye large and circular, interorbital width wider than eye diameter. Opercular spine absent. Mouth large. Villiform teeth in bands present on both jaws, vomer, and palatine, but tongue toothless. Two separate dorsal fins, an isolated spine present between first and second dorsal fins (reduced in large specimens). Anal-fin origin posterior to second dorsal-fin origin. Pectoral and pelvic fins short, not reaching anus. Anus located below second dorsal-fin origin. Caudal fin deeply forked. Scales weakly ctenoid, deciduous. Lateral line single, conspicuous. Body and all fins dark brown. Head dark brown with blue purplish reflection, oral cavity black.

Distribution  Eastern Atlantic including Mediterranean, northwestern Atlantic, Indian Ocean, Australia, New Zealand (Mayer, 1974; Abramov, 1992).

Remarks  This species is similar to E. angustifrons Abramov and Manilo, 1987, but differs in having 23–26 gill rakers (vs. 33–36 in E. angustifrons), deeper body depth (ca. 1/4 of SL vs. ca. 1/5 of SL), and larger size (reaching at least 70 cm SL vs. smaller than 40 cm SL). Furthermore, E. telescopus differs from other congeners in the area in the counts of gill rakers (23–26 vs. 28–34 in E. denticulatus Dieuzeide, 1950) and lateral-line scales (46–50 vs. 35–37 in E. exodon Okamoto and Motomura, 2012), and the absence of an opercular spine [vs. present in E. robustus (Barnard, 1927)] （Okamoto 2012; Okamoto and Motomura 2012, 2013）. The isolated dorsal-fin spine reduces in size with growth, becoming difficult to discern in large specimens. Epigonus telescopus is the largest species of the genus (85 cm in total length) and is utilised commercially in some areas.

(M. Okamoto)