シマガツオ科 Bramidae Pomfrets
30 ニシヒレジロマンザイウオ（新称）
Taractichthys longipinnis
(Lowe, 1843) Big
Scale Pomfret
Specimen
examined: 3 (SNFR 16442, 16600, 17023; 535–586 mm
SL, 581–643 mm FL, 358–580 m depth.
Counts:
D 36–37; A 27–28; P1 19–20; P2 I, 5; GR 4–6+12–14=16–19;
PDS 33–35; LS 41–45; V 20–21+24–26=45–46. Measurements:
head length 30.0–32.4% SL, 27.4–29.8% FL; body depth 49.7–53.1% SL, 45.3–48.4% FL;
eye diameter 24.7–25.4% HL; interorbital width 35.9–38.6%
HL; snout length 29.8–30.6% HL; upper jaw length 51.0–53.2% HL; lower jaw
length 53.0–58.1% HL; caudal peduncle length 44.2–53.1% HL; caudal peduncle depth
21.3–23.3% HL; pectoral-fin length 35.4–40.3% SL, 32.2–37.1% FL; pelvic fin
length 26.3–32.4% HL.
計数形質：36–37軟条；臀鰭27–28軟条；胸鰭19–20軟条；腹鰭1棘，5軟条；鰓耙数4–6 + 12–14=16–19；背鰭前方鱗数 33–35；縦列鱗数41–45；脊椎骨数20–21+24–26=45–46．計測形質：頭長30.0–32.4%
SL, 27.4–29.8% FL；体高49.7–53.1%
SL, 45.3–48.4% FL；眼径24.7–25.4%
HL；両眼間隔35.9–38.6% HL；吻長29.8–30.6% HL；上顎長51.0–53.2%HL；下顎長53.0–58.1% HL；尾柄長44.2–53.1% SL；尾柄高21.3–23.3% HL；胸鰭長35.4–40.3% SL,
32.2–37.1% FL；腹鰭長26.3–32.4%
HL.
特 徴 頭部および体は側扁する．体は卵円形．頭部の背縁は強く弧を描く．吻は丸い．眼は楕円形で，上下に長い（成魚）．両顎の歯は円錐歯で内側に曲がり，歯帯をなす．鋤骨歯はない．口蓋骨歯は狭い歯帯をなす．尾柄背面および腹面の尾鰭基部直前に，左右に走る溝がある．背鰭始部は胸鰭基部の上方または僅かに後方．背鰭および臀鰭の前部は顕著に伸長して鎌形になる．背鰭および臀鰭は鱗に覆われ，倒せない．尾鰭は深く湾入する．胸鰭は頭長より長く，臀鰭伸長部の上方に達する．腹鰭は短く頭長の1/3以下で，胸鰭基部の直下にある．腹鰭液部に突起が発達する．鱗に棘がない（成魚）．体側中央部の鱗は上下に長い．尾鰭上の鱗は尾柄部の鱗より著しく小さい．鰓耙は長く，扁平．側線は不明瞭．体は灰褐色で，背部は暗色．鰭は暗褐色．尾鰭後縁は白い．
分 布 大西洋の熱帯から温帯域 (González-Lorenzo
et al., 2013)；ニュージーランド (Paulin, 1981)；南西インド洋海嶺（本研究）．
備 考 本種は，インド・太平洋に分布するヒレジロマンザイウオTaractichthys steindachneri
(Döderlein, 1883) によく似るが，縦列鱗数が多いこと (40より多vs.
34–40)，背鰭前方鱗数が多いこと
(33–37 vs. 21–29)で区別できる (Last
and Moteki, 2001)．体長300–400
mm では，本種の眼は円形に近いがヒレジロマンザイウオの眼は明瞭な楕円形である (Mead,
1972)．Smith
(1986) は，「インド・太平洋からの本種の記録はヒレジロマンザイウオの誤同定と考えられる」と述べたが，本種はインド洋に出現することが本標本の記録により確認された．小型の個体（体長400
mm 以下）では，体の鱗に棘がある (Mead,
1972)．
(星野)
Description
Head
and body compressed. Body oval. Dorsal profile of head strongly convex. Snout
rounded. Eye elliptical, vertically higher in adults. Teeth of both jaws
conical and curved medially, in a band. Vomerine
teeth absent; palatine teeth in a narrow band. A transverse groove present on
dorsal and ventral surfaces of caudal peduncle just anterior to caudal-fin
base. Dorsal-fin origin above pectoral fin or slightly posterior. Anterior part
of dorsal and anal fin elongated to form a falcate lobe. Dorsal and anal fins
covered with scales, not depressible. Caudal fin deeply emarginate.
Pectoral fin longer than head length, extending to above anal-fin lobe. Pelvic
fin short, 1/3 of head length or shorter, located just below pectoral-fin base.
Axillary process prominent. Scales without spines (in
adults), vertically elongated on mid-lateral part of body. Scales on caudal fin
much smaller than those on caudal peduncle. Gill rakers
on first arch elongate, flattened. Lateral line obscure. Body brownish gray;
darker dorsally; fins dark brown; posterior margin of caudal fin white.
Distribution
Tropical
and temperate Atlantic (González-Lorenzo et al., 2013);
Remarks This species closely resembles Taractichthys steindachneri (Döderlein, 1883), which occurs in the Indo-Pacific, but can
be distinguished by having more longitudinal scales (more than 40 vs. 34–40)
and more predorsal scales (33–37 vs. 21–29) (Last and
Moteki, 2001). At 300–400 mm SL, the eye is nearly
circular in T. longipinnis,
but strongly elliptical in T. steindachneri (see Mead, 1972). Smith (1986) stated
that “references to T. longipinnis in the Indo-Pacific are considered
misidentification of T. steindachneri,” but T.
longipinnis is confirmed to occur in the
(K. Hoshino)