The “Hirase’s Slit Shell” is a thick-shelled pleurotomariid with flamboyant flame-like patterns, native to the Western Pacific. It generally ranges from central Honshu, Japan to East China Sea and Taiwan, though very rare records exist from as far south as the Philippines.
A carnivorous grazer feeding on sponges and soft corals, it is found in rather deep water around -50~300m. As it is a relatively common species especially from Japan to East China Sea and frequently brought up as by-catch in this area, it is a famous species and perhaps the most easily obtained species of the slit shells, most species of which are very rare and difficult to obtain.
Quite variable in shell form especially the height/width ratio and the swollenness of whorls though rather consistent in sculpture and pattern, the name M. h. yamamotoi (Yamamoto, 1993) is a synonym given to a compressed form. An uncommon albinistic form is known across its range. Typical shell diameter is around 70mm, very large specimens may exceed 120mm. It is most similar to the much rarer Mikadotrochus beyrichii (Hilgendorf, 1877) endemic to Japan, but they are easily distinguished by boths sculpture and pattern. – From Chong Chen’s post
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