アユカワウミコチョウ Siphopteron fuscum (Baba & Tokioka, 1965)

アユカワウミコチョウ Siphopteron fuscum
Photographed by
黒田貴司
Location
日本>房総半島>鋸南>明鐘
Date
2012/03/10
Size
10mm
Depth
7.0m
Water temperature
14.0℃
分布:西太平洋

日本からのみの観察になるが、本州産と琉球列島産では体色や体長に変異がある。
本州産は体色が暗褐色で、腹足や尾は半透明の白色。
頭楯、側足、内臓嚢に白色の斑紋が入る。尾の正中線上には白色の縦線が入る。
側足縁や腹足縁、内臓嚢後部の突起の先端は橙色から朱色になる。
体長は10mmに達する。
対して琉球列島産は体色が全体的に薄く淡くなり、体長は3mm程度と小型。

和名は、Baba K. & Tokioka, 1965 にて提唱された。

沖縄の個体が S. fuscum であると同定したのはClay CarlsonであるとBob Bolland の Okinawa Slug Site に書かれている。
Baba K. & Tokioka T. Two more new species of Gastropteron from Japan, with further notes on G. flavum T. & B. (Gastropoda: Opisthobranchia). Publications of the Seto Marine Biological Laboratory, 12(5 The coloration of the type in life is extremely complicated and graceful. The dorsal hump is deep chocolate brown spotted sparsely with white. The lower surface of each parapodium is also deep chocolate brown with a few, bold, irregular markings of white towards the free margin. The horn-like protuberance of the dorsal hump is tinted with vermilion distally. There is a narrow vermilion band along the entire length of the parapodial margin and on the border line between each paradium and foot. The tail is also edged with vermilion. On the cephalic shield, the presence of a transverse vermilion band running parallel to the anterior edge is the first to be noted. Then follow a pair of longitudinal bands of the same colour which extend from the level of the transverse colour band to near the tip of the funnel converging distally and holding a narrow streak of snow white in between. The lateral edges of the shield are stained with deep chocolate brown. The free margin of the funnel is vermilion. The dorso-median crest is vermilion-tinted at the distal and chocolate brown at the proximal. The rest of the body including the sole is translucent and whitish in ground colour. On the underside of the tail there is a snow white streak in the median line which indicates exactly the position of the pedal gland.
Baba K. & Tokioka T. Two more new species of Gastropteron from Japan, with further notes on G. flavum T. & B. (Gastropoda: Opisthobranchia). Publications of the Seto Marine Biological Laboratory, 12(5

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