noun
freshwater black snail; marsh snail
A small freshwater snail native to East Asia, often found in clean streams and rivers. Semisulcospira bensoni is a specific species, but the term may be used broadly for similar snails.
カワニナはきれいな川にすんでいる。
Freshwater black snails live in clean rivers.
ホタルの幼虫はカワニナを食べる。
Firefly larvae eat freshwater black snails.
Rare kanji form; 貝子 is an old term for shellfish.
The name likely derives from 川 (kawa, 'river') and 蜷 (nina, an old word for spiral-shelled snails). The exact origin is uncertain.