ヒウチダイ科 Trachichthyidae             Rouphies, Slimeheads

 





SNFR 19229, 203 mm SL.


13 シソヒウチ

Hoplostethus mediterraneus Cuvier, 1829     Silver Roughy, Mediterranean Slimehead

 

Specimens examined: 8 (SNFR 19229–19233, SNFR 199234 [n=3]; 144–203 mm SL), 618–792 m depth.

Counts: D V–VI, 13–14; A III, 9–10; P1 15; P2 I, 6; GR 7–8+16–17=24–25; LLS 27–28; V 11+15=26. Measurements: head length 36.8–39.5% SL; body depth 42.0–49.5% SL; eye diameter 29.1–34.6% HL; interorbital width 28.5–31.4% HL; snout length 20.1–23.0% HL; upper-jaw length 64.1–69.2% HL; lower-jaw length 65.8–71.9% HL; caudal-peduncle length 53.3–60.8% HL; caudal-peduncle depth 27.4–33.2% HL; pectoral-fin length 82.1–96.4% HL; pelvic-fin length 56.7–64.7% HL.

 

計数形質:背鰭5–6棘,13–14軟条;臀鰭3棘,9–10軟条;胸鰭15軟条;腹鰭1棘,6軟条;鰓耙数7–8+16–17=24–25;側線鱗数27–28;脊椎骨数11+15=26計測形質:頭長36.8–39.5% SL;体高42.0–49.5% SL;眼径29.1–34.6% HL;両眼間隔28.5–31.4% HL;吻長20.1–23.0% HL;上顎長64.1–69.2%HL;下顎長65.8–71.9% HL;尾柄長53.3–60.8% SL;尾柄高27.4–33.2% HL;胸鰭長82.1–96.4% HL;腹鰭長56.7–64.7% HL.

特 徴 体は卵形で側扁する.体の背部輪郭はゆるく湾曲する.頭部は体長の1/3より大.吻部は鈍く,円い.眼は大きく,眼径は頭長の約1/3.頭部,特に眼の周囲の骨には深い粘液溝が発達する.鰓蓋の上方(後側頭骨)および前鰓蓋骨の隅角部にそれぞれ後ろ向きの強い1棘がある.主鰓蓋骨に水平で顕著な稜状の突起がある.口は大きく,斜め.両顎の歯は微小で,広い歯帯をなし,外面に露出する.鋤骨歯はない.口蓋骨歯がある.鰓耙は長い.背鰭は1基.背鰭第1棘条はごく短く,最終棘条が最長.臀鰭第1棘条はごく短く,第3棘条が最長.尾鰭は二叉し,上葉および下葉は尖る.胸鰭は長く,臀鰭第3棘条に達する.腹鰭棘条は長い.腹部正中線上の稜鱗はよく発達し,9–15個.体側鱗は剥がれやすく,弱い櫛鱗または円鱗.側線鱗は体側鱗よりはるかに大きく,菱形.体および頭部は銀白色で,体背部は赤みを帯びた褐色.鰭は淡赤色.背鰭前部の縁辺および尾鰭後端は黒みがかる.口腔および鰓腔は暗色.

分 布 北大西洋西部(北米沿岸),大西洋東部(アイスランドからモロッコ,ナミビア),南アフリカ,オーストラリア南岸,ニュージーランド(Heemstra, 1986; Maul, 1986; Moore, 2002; Golani and Bogorodsky, 2010)

備 考 大きく菱形の側線鱗はヒウチダイ属Hoplostethusの特徴 (Moore and Paxon, 1999).南インド洋西部には,本種と同属のオレンジラフィー H. atlanticus Collett, 1896,クロヒウチH. melanopus (Weber, 1913)H. tenebricus Kotlyar, 1980およびH. mikhailini Kotlyar, 1986が出現するが,本種は銀白色の体と淡赤色の鰭を持つことでこれらと区別できる(Heemstra, 1986; Kotlyar, 1986; 清水, 1990).本種は,よく発達した腹部正中線上の稜鱗を持つことでオレンジラフィー,クロヒウチおよびH. tenebricus(稜鱗は小さいか,またはない)と区別できる(Kotlyar, 1986)

(星野)

 

Description  Body ovate, compressed. Dorsal profile of body gently arched. Head larger than 1/3 of SL. Snout blunt, rounded. Eye large, about 1/3 of head. Deep mucous cavities well developed in head bones, especially around eye. A strong, posteriorly directed spine present above gill opening (on post-temporal), and at corner of preopercle. A prominent horizontal ridge on opercle. Mouth large, oblique. Teeth in jaws minute, in broad band. Vomer toothless. Palatine with band of teeth. Gill rakers long. Dorsal fin single; 1st spine very short, last longest. First anal-fin spine very short, third longest. Caudal fin forked, lobes pointed. Pectoral fin long, reaching 3rd anal-fin spine. Pelvic-fin spine long. Abdominal scutes on ventral midline well developed, 9–15. Body scales deciduous, weakly ctenoid or cycloid. Lateral-line scales much larger than body scales, diamond-shaped. Body and head silvery, dorsal part of body reddish brown. Fin membranes light red, anterior dorsal-fin margin and tips of caudal lobes blackish. Buccal and gill cavities dark.

Distribution  Western North Atlantic (North American coast), eastern Atlantic (from Iceland to Morocco, Namibia), South Africa, off south coast of Australia and New Zealand (Heemstra, 1986; Maul, 1986; Moore, 2002; Golani and Bogorodsky, 2010).

Remarks  Enlarged and diamond-shaped lateral-line scales are characteristic of the genus Hoplostethus (Moore and Paxton, 1999). Five species of Hoplostethus have been reported from the South Indian Ocean: H. mediterraneus, H. atlanticus Collett, 1889 (= Orange Roughy), H. melanopus (Weber, 1913), H. tenebricus Kotlyar, 1980, and H. mikhailini Kotlyar, 1986. H. mediterraneus is distinguished from the other 4 species in having a silvery body and reddish fins (Heemstra, 1986; Kotlyar, 1986; Shimizu, 1990). This species also differs from H. atlanticus, H. melanopus and H. tenebricus in having well-developed abdominal scutes (small or absent in the other three species) (Kotlyar, 1986).

(K. Hoshino)

 



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