starfish; sea star
General term for any echinoderm of the class Asteroidea. In everyday Japanese, ヒトデ is the standard word.
I found a starfish on the beach.
Starfish are known for their high regenerative ability.
northern Pacific seastar
Specifically Asterias amurensis, a common species in northern Japan. Often used in biological or fishing contexts.
In Hokkaido, the northern Pacific seastar sometimes causes damage to fisheries.
I picked up a starfish on the beach.
In everyday speech, small sea creatures are often counted with 匹; some speakers may also use a more specialized counter depending on context.
Obscure kanji spelling; not recommended for learners.