カワビシャ科 Pentacerotidae
Armourheads
33 ケープツボダイ（新称）
Pentaceros capensis
Cuvier in Cuvier and
Specimens
examined: 5 (SNFR 19320–19323, 19338; 125–181 mm
SL), 572–988 m depth.
Counts:
D XII, 12; A V, 8–9; P1 16–17; P2
I, 5; GR 7–9+16–18=23–27; LLS 44–48; V 12+13=25. Measurements: head length 37.9–39.3% SL; body depth 45.3–50.6% SL;
eye diameter 33.7–38.0% HL; interorbital width 28.0–30.0%
HL; snout length 36.4–39.2% HL; upper-jaw length 29.1–31.1% HL; lower-jaw
length 37.3–39.3% HL; caudal-peduncle length 30.3–32.1% HL; caudal-peduncle
depth 30.1–32.1% HL; pectoral-fin length 85.9–94.1% HL; pelvic-fin length 69.7–77.4%
HL.
計数形質：背鰭12棘12軟条；臀鰭5棘8–9軟条；胸鰭16–17軟条；腹鰭1棘5軟条；鰓耙数7–9+16–18=23–27；側線鱗数44–48；脊椎骨数12+13=25．計測形質：頭長37.9–39.3%
SL；体高45.3–50.6% SL；眼径33.7–38.0% HL；両眼間隔28.0–30.0% HL；吻長36.4–39.2% HL；上顎長29.1–31.1% HL；下顎長37.3–39.3% HL；尾柄長30.3–32.1% SL；尾柄高30.1–32.1% HL；胸鰭長85.9–94.1% HL；腹鰭長69.7–77.4% HL.
特 徴 体は強く側偏する．体の背縁は背鰭軟条部で強く弧を描く．胸部腹面は平坦．頭部は多数の溝をもつ粗雑な骨で広く覆われる．吻は尖る．口は傾めで小さい．口唇および頤に微細なひげが密集する．両顎歯は小円錐歯で，歯帯をなす．眼は大きい．背鰭は連続し，基部は長い．背鰭棘条は強大で，基部は体背縁の溝に収まり，第3棘または第4棘が最長．臀鰭基底長は短い．臀鰭棘条は強大で，基部は体腹縁の溝に収まり，第2棘が最長．尾柄は短く，尾柄長は尾柄高とほぼ等しい．尾鰭は截形または僅かに凹む．胸鰭は長く，尖る．腹鰭は円く，倒すと後端は臀鰭始部を超える．腹鰭棘条は強大で長い．側線は強く湾曲し，尾柄部では直線状．鱗は櫛鱗．項部，頬部，胸部の鱗は厚く硬い．胸部の鱗は互いに密着する．側線上方鱗数は6–8，側線下方鱗数は28–31．峡部から腹鰭始部までの正中線上に20–22枚の鱗が並ぶ．体は全体に淡褐色で，体の下部が黄色みを帯びる個体もいる．背鰭鰭膜の縁辺は黒みがかる．腹鰭の鰭膜は黒い．
分 布 アフリカ南部沿岸の，ポートノラス（南アフリカ大西洋岸）から喜望峰，クワズール・ナタール州（南アフリカ連邦），モザンビークまで，水深73–183m (Hardy, 1983)．南西インド洋海嶺，マダガスカル海嶺（本研究）．
備 考 本種はキマダラツボダイPentaceros decacanthus
Günther,
1859 およびツボダイ Pentaceros japonicus
Döderlein,
1883 に似るが，側線上方鱗数が少ないこと (6–8 対 8–9)，峡部から腹鰭始部までの正中線上に並ぶ鱗が少ないこと (14–22
対 21–26)で区別できる (Hardy,
1983; 本研究)．ミナミクサカリツボダイPentaceros richardsoni
Smih,
1844とは，体高がより高いこと，背鰭棘条が少ないこと等で区別できる (Hardy, 1983)．本研究の採集水深(572–988
m ) は従来の記録 (70–300
m)よりはるかに深い．
(星野)
Description Body
strongly laterally compressed. Dorsal profile strongly rounded under soft-rayed
part of dorsal fin. Breast flat ventrally. Head predominantly covered with rugose, striated bones. Snout pointed. Mouth oblique,
small. Lips and chin finely villose. Teeth of both
jaws short, conical, forming a band. Eye large. Dorsal fin continuous, its base
long. Dorsal-fin spines robust, their bases embedded in a prominent groove;
third or fourth spine longest. Anal-fin base short. Anal-fin spines robust,
their bases embedded in a prominent groove, second spine longest. Caudal peduncle
short, as long as deep. Caudal fin margin truncate or slightly concave.
Pectoral fin elongate, pointed. Pelvic fin rounded, extending beyond anal-fin
origin when appressed. Pelvic-fin spine robust and
long. Lateral line strongly arched, straight at caudal peduncle. Scales ctenoid; those on nape, cheek, and breast thick and hard;
those on breast juxtaposed; 6–8 scales above lateral line, 28–31 below; 20–22
scales from isthmus to level of pelvic-fin origin along ventral midline. Entire
body light brown, frequently with yellowish tinge on ventral part of body below
pectoral-fin base. Dorsal fin membrane with dusky margin. Pelvic fin membrane
dark.
Distribution Southern
African waters, from Port Nolloth to
Remarks This
species resembles Pentaceros decacanthus Günther,
1859 and Pentaceros japonicus Steindachner, 1883, but can be distinguished in having fewer
scales above the lateral line (6–8 vs. 8–9) and along the ventral midline
between the throat and the level of the pelvic-fin base (14–22 vs. 21–26)
(Hardy, 1983; present study). It is easily distinguished from Pentaceros richardsoni
Smith, 1844 in having a deeper body and fewer dorsal-fin spines (Hardy, 1983).
The capture depth in the present study (572–988 m) is much deeper than previous
records (70–300 m).
(K.
Hoshino)