フサアンコウ科 Chaunacidae Coffinfishes, Frogmouths
11 フサアンコウ属の1種-1
Chaunax sp.
1
Specimens
examined: 5 (SNFR 19261–19265, 141–288 mm SL), 637–950 m depth (bottom trawl).
Counts:
D III-12; A 7; P1 14; GRi (1st arch) 11–13
(3–4+8–9); lateral-line neuromasts: supraorbital series AB 9–10, infraorbital
series CD 6, mandibular series EF 6, pectoral series
GH 12; lateral-line proper BI 31–32. Measurements
(all expressed as % SL): HL
41.4–43.5; head width 19.0–20.4; pre-dorsal length 49.9–53.3; pre-gill opening
length 59.9–63.5; upper-jaw length 20.6–22.1; illicial
length 3.6–5.5; illicial trough length 4.5–5.8; eye
diameter 6.4–7.2; post-dorsal fin length 16.5–18.3; post-anal fin length
14.1–15.3; caudal-peduncle depth 8.8–9.5; caudal-fin length 25.9–29.4.
計数形質：背鰭 3棘12軟条；臀鰭7軟条；胸鰭14軟条；鰓耙数（第1鰓弓）11–13
(3–4+8–9)；側線感丘数：眼上AB 9–10，眼下CD
6，下顎EF
6，胸部GH
12，側線後方BI
31–32. 計測形質：（全て%
SL） 頭長 41.4–43.5；頭幅 19.0–20.4；背鰭前長 49.9–53.3；鰓孔前長 59.9–63.5；上顎長 20.6–22.1；誘引突起長3.6–5.5；誘引突起溝長 4.5–5.8；眼径 6.4–7.2；背鰭後長 16.5–18.3；臀鰭後長 14.1–15.3；尾柄高 8.8–9.5；尾鰭長 25.9–29.4.
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．吻上の誘引突起は太短く，誘引突起溝は深く窪む．擬餌状体は多数の細長い毛状皮弁を備える．擬餌状体の上面が暗色（白色と灰色から暗色の皮弁が混在），下面が白色．皮膚は極めてゆるく，微小な棘状鱗で密に覆われる．糸状皮弁は誘引突起溝周辺でやや密に，体表で極めて疎らに分布する．側線系は溝状でよく発達する．生鮮時には，背面が一様に赤色，または橙色で不規則な黄色斑点や赤色斑紋を多数もち，腹面は白色．誘引突起と誘引突起溝は深紅から濃橙色（液漬標本では黒色）．
分 布 インド洋南西部（マダガスカル海嶺）．底生性で採集水深637–950
m．（本研究）．
備 考 現在知られるフサアンコウ属の22種は3種群に分類され(Ho
and Last, 2013; Ho et al., 2013,
2015)，本標本は誘引突起溝が暗色で深く窪むことからChaunax pictus種群（3種を含む）に属する．このうち，調査海域を含むインド・西太平洋に分布するChaunax penicillatus
McCulloch, 1915に誘引突起溝と擬餌状体の特徴が最も類似するが，胸鰭鰭条数14（vs.
11–13），第1鰓弓鰓耙数11–13（vs.
13–14），側線感丘数BI
31–32 (vs. 35–40)，誘引突起長3.6–5.5 % SL（vs.
1.5–2.2% SL）や擬餌状体の形態などで異なる（Ho et al., 2013; 本研究）．また，同種群のChaunax stigmaeus
Fowler, 1946とChaunax pictus
Lowe, 1846とは，擬餌状体と誘引突起の形状や色，体色などで異なる（Caruso,
1989）．本標本は未記載種の可能性があるが，さらなる検討を要する．
（遠藤）
Description
Head
and body globose, somewhat depressed, conical posteriorly. Mouth large, nearly vertical. Jaws, vomer, and palatine with tooth bands. Illicium
on snout short, stout, retractable in deeply concave illicial
trough. Esca with numerous long cirri, blackish above
(mixed with white, gray or dark cirri) and white below. Skin very loose,
densely covered with fine spinoid scales. Some
thread-like dermal flaps present on snout around illicial
trough, very sparse on body. Lateral-line system grooved, well developed. When
fresh, body uniformly reddish or orange with many irregular yellowish spots and
reddish markings dorsally, white ventrally. Illicium
and illicial trough deep red to deep orange (blackish
in preserved specimens).
Distribution Western
Remarks Chaunax
is composed of 22 species, subdivided into three species-groups (Ho et al., 2013, 2015). The present specimens
belong to the Chaunax pictus
species-group (3 species) by sharing a dark illicial
trough that is deeply concave. They are most similar to C. penicillatus McCulloch, 1915, which occurs
in the Indo-West Pacific (including the study area), in having the unique illicial trough and esca with
numerous cirri, but differ in the counts of pectoral-fin rays (14 vs. 11–13),
gill-rakers on the first arch (11–13 vs. 13–14), and
lateral-line neuromasts of BI (31–32 vs. 35–40), and
in illicial length (3.6–5.5 % SL vs. 1.5–2.2 % SL),
features of the illicium and esca,
and other characters (Ho et al.,
2013; this study). The present specimens are distinguished from Chaunax pictus Lowe,
1846 and Chaunax stigmaeus
Fowler, 1946 of the same species-group by a few of characters of the illicium and coloration (Caruso, 1989). The present
specimens may represent an undescribed species, but
further research is needed.
(H.
Endo)