noun
Unio douglasiae (freshwater mussel)
A species of freshwater mussel native to East Asia. The name is usually written in katakana as イシガイ.
イシガイは日本の川や湖に生息する淡水二枚貝です。
The Unio douglasiae is a freshwater bivalve that inhabits rivers and lakes in Japan.
The name likely derives from 石 (ishi, 'stone') and 貝 (kai, 'shellfish'), referring to its hard, stone-like shell. The exact origin is uncertain.