メバル科　Sebastidae                                Rockfishes

 

22 タイセイヨウユメカサゴ（新称）

Helicolenus dactylopterus (Delaroche, 1809)              Blackbelly Rosefish

 

Specimen examined: 10 (SNFR 19239, 19298–19302; 95.1–144 mm SL), 348–702 m depth.

Counts: D XII, 11–13; A III, 5; P₁ 19–20 (8–9 rays branched); P₂ I, 5; GR 8–9+19–20=27–29; PLS 27–29. Measurements: head length 39.2–42.3% SL; body depth 31.8–35.0% SL; orbit diameter 33.6–39.1% HL; interorbital width 10.4–12.2% HL; snout length 21.8–25.1% HL; upper-jaw length 52.1–55.6% HL; caudal-peduncle length 17.3–20.1% SL; caudal-peduncle depth 9.8–10.6% SL; longest dorsal-fin spine length 17.4–18.1% SL (third or fourth); 1st anal-fin spine length 5.8–7.0% SL; second anal-fin spine length 15.6–17.2% SL; 3rd anal-fin spine length 13.7–16.4% SL; pectoral-fin length 29.3–32.2% SL; pelvic-fin spine length 14.1–15.6% SL; longest pelvic-fin soft ray length 23.3–25.9% SL; caudal-fin length 26.6–28.2% SL.

 

計数形質：背鰭12棘，11–13軟条；臀鰭3棘，5軟条；胸鰭19–20軟条（8–9分枝軟条）；腹鰭1棘，5軟条；鰓耙数8–9+19–20=27–29；有孔側線鱗数27–29．計測形質：頭長39.2–42.3% SL；体高31.8–35.0% SL；眼窩径33.6–39.1% HL；両眼間隔10.4–12.2% HL；吻長21.8–25.1% HL；上顎長52.1–55.6% HL；尾柄長17.3–20.1% SL；尾柄高9.8–10.6% SL；最長背鰭棘長17.4–18.1% SL（第3または第4棘）；第1臀鰭棘長5.8–7.0% SL；第2臀鰭棘長15.6–17.2% SL；第3臀鰭棘長13.7–16.4% SL；胸鰭長29.3–32.2% SL；腹鰭棘長14.1–15.6% SL；腹鰭最長軟条長23.3–25.9% SL；尾鰭長26.6–28.2% SL．

特　徴　体はやや長く側扁する．頭は大きい．口は大きく，上顎後端は眼の後縁下にほぼ達する．鋤骨と口蓋骨に歯がある．鼻棘，眼前棘，眼上棘，眼後棘，耳棘，頭頂棘，頸棘がそれぞれ1本ずつある．主鰓蓋骨棘は2本．前鰓蓋骨棘は5本．涙骨および眼下隆起線に棘はない．後頭窩はない．体と頭は櫛鱗で被われる．胸部および腹部は円鱗で被われる．背鰭，臀鰭および腹鰭の棘は強く，毒腺が収まっていたと考えられる溝を有する．背鰭棘は比較的短い．胸鰭は大きく，後縁は丸い．尾柄は短くやや太い．尾鰭はわずかに湾入する．頭と体は一様に赤く，腹部は白みがかる．背鰭と体の背部に不規則な暗色斑がある．口腔と鰓腔は黒色．

分　布　地中海，大西洋およびインド洋南西部の通常，水深200–650 m（Eschmeyer, 1969；Poss and Eschmeyer, 2003）．

備　考　本海域に同属他種は分布しない（Eschmeyer, 1986）．本種は体側の模様と，口腔および鰓腔が黒色であることで本海域の他のメバル科および近縁のフサカサゴ科魚類と容易に識別される．本稿ではPoss and Eschmeyer (2003)やAboim et al. (2005)など近年の研究にしたがってH. dactylopterusと大西洋南西部から知られるラプラタユメカサゴHelicolenus lahillei Norman, 1937を独立種として認めたが，Eschmeyer (1969)やNakamura et al. (1986)など複数の研究では両名義種は亜種関係とされる．

（松沼）

 

Description  Body moderately elongate and compressed. Head large. Mouth large, posterior margin of maxilla almost reaching level of posterior margin of orbit. Vomer and palatine with tooth bands. One nasal spine, one preocular spine, one supraocular spine, one postocular spine, one tympanic spine, one parietal spine, and one nuchal spine. Two opercular spines. Four preopercular spines. Lacrimal bone and suborbital ridge without spines. Occipital pit absent. Body and head covered with ctenoid scales; thorax and abdomen with cycloid scales. Dorsal-, anal-, and pelvic-fin spines strong, with grooves (most likely associated with venom glands). Dorsal-fin spines relatively short Pectoral fin large, rounded. Caudal peduncle short, moderately deep. Caudal fin slightly emarginate. Head and body reddish, whitish ventrally. Irregular dark markings on dorsal-fin membrane and dorsal portion of body. Buccal and gill cavities black.

Distribution  Mediterranean, Atlantic and western South Indian oceans, including South Africa. Found primarily in depths of 200–650 m (Eschmeyer, 1969; Poss and Eschmeyer, 2003).

Remarks  No congeners are recorded from the Southwestern Indian Ocean (Eschmeyer, 1986). The species is readily distinguished from other sebastids and fishes of the related family, Scorpaenidae, by having dark markings on sides of the body and the black buccal and gill cavities. Following recent studies, e.g., Poss and Eschmeyer (2003) and Aboim et al. (2005), H. dactylopterus and its congener, Helicolenus lahillei Norman, 1937, known from the Southwestern Atlantic Ocean, are tentatively regarded here as distinct species rather than subspecies; however, several researchers, including Eschmeyer (1969) and Nakamura et al. (1986), have treated the latter as a subspecies of the former.

(M. Matsunuma)