フサアンコウ科 Chaunacidae
Coffinfishes, Frogmouths
12 フサアンコウ属の1種-2
Chaunax
sp. 2
Specimens
examined: 3 (SNFR 19326–19328, 122–232 mm SL),
643–702 m depth (bottom trawl).
Counts:
D III-12; A 7; P1 13; GRi 12 (3+9); lateral-line
neuromasts: AB 11, CD 6–7, EF 6, GH 12–13, BI 35–36. Measurements (all expressed as % SL): HL 39.3–41.4; Head width 16.4–18.6;
pre-dorsal length 46.7–50.4; pre-gill opening length 61.2–61.4; pre-preopercular length 26.5–27.1; upper-jaw length 19.6–20.7; illicial length 4.3–6.6; illicial
trough length 5.9–9.0; eye diameter 5.9–6.5; post-dorsal fin length 17.1–18.4;
post-anal fin length 15.6–19.2; caudal-peduncle depth 7.8–8.5; caudal-fin
length 27.7–31.2.
計数形質：背鰭 3棘12軟条；臀鰭7軟条；胸鰭13軟条；鰓耙数（第1鰓弓）12
(3+9)；側線上感丘数：AB
11；CD
6–7；EF
6；GH
12–13；BI 35–36．計測形質：（全て%
SL） 頭長39.3–41.4；頭幅16.4–18.6；背鰭前長 46.7–50.4；鰓孔前長 61.2–61.4；前鰓蓋骨前長 26.5–27.1；上顎長 19.6–20.7；誘引突起長4.3–6.6；誘引突起溝長 5.9–9.0；眼径 5.9–6.5；背鰭後長 17.1–18.4；臀鰭後長 15.6–19.2；尾柄高 7.8–8.5；尾鰭長 27.7–31.2．
特 徴 頭部と体は球形でやや縦扁し，尾部は円錐形．口は大きく上向き．両顎，鋤骨と口蓋骨に歯帯をもつ．誘引突起は細長く，誘引突起溝は極めて浅い．擬餌状体は小さく，微小な皮弁をもつ．皮膚はゆるく，体は微小な棘状鱗で密に覆われ，腹部の鱗は極めて小さい．側線系は溝状でよく発達し，各側線鱗では感丘を上下から被うように2–7対（多くは3−4対）の棘が延びる．頭部と体の下縁および尾部の側線付近には長い糸状皮弁をもつ．生鮮時の背面は赤みの橙色で，黄色斑点や楕円形の斑紋が散在する．腹面は白色．体の糸状皮弁は白色．誘引突起と誘引突起溝は赤橙色（液浸標本では黒褐色）．擬餌状体は白色から灰色．
分 布 インド洋南西部（南西インド洋海嶺）．（本研究）．
備 考 本標本はインド洋から記録のある本属9種とは，体色や斑紋，誘引突起や誘引突起溝，擬餌状体の形態，いくつかの計数形質や計測形質などの特徴でいずれとも異なる（Ho
and Last, 2013; Ho et al., 2013, 2015）．また，本標本は誘引突起溝がごく浅いこと，および側線鱗の感丘付近にある棘数からインド•太平洋に分布するC. fimbriatus種群に含まれ，この種群の6種とは体色と斑紋などで異なる(Ho
and Last, 2013; Ho et al., 2013)．よって本標本は未記載種の可能性があるが，更なる検討を要する．
（遠藤）
Description
Head
and body globose, somewhat depressed, caudal part
conical. Mouth large, nearly vertical. Jaws, vomer,
and palatines with tooth bands. Illicium long,
slender, located on flat illicial trough. Esca small with fine cirri. Skin very loose, body densely
covered with fine spinoid scales, those on belly
minute. Lateral-line system grooved, well developed, each lateral-line scale
bridging neuromast with 2–7 pairs of spinules (mostly 3–4). Many long dermal filaments present
along ventrolateral margins of head and body, and
around posterior lateral line. In fresh condition, whole body reddish orange
dorsally with many yellow spots and oval markings, white ventrally. Filaments
on body white. Illicium and ilicial
trough reddish orange (dark brown in preservative). Esca
white to gray.
Distribution Western
South Indian Ocean (South West Indian Ridge) (present study).
Remarks The present specimens differ from nine
known species of Chaunax
recorded from the Indian Ocean by features of coloration and markings, illicium and esca, illicial trough, and some counts and proportions (Ho and
Last, 2013; Ho et al., 2013, 2015).
They belong to the Chaunax fimbriatus
species-group in having the flat illicial trough, each
lateral-line scale bridging a neuromast with 2–7
pairs of the spinules (mostly 3–4), but can be
distinguished from the six species of the same species-group by body coloration
and markings, and other characters (Ho and Last, 2013; Ho et al., 2013). The present specimens probably represent an undescribed species, but further investigations are needed.
(H.
Endo)