Acartia clausi is a species of marine copepod belonging to the family Acartiidae. This species was previously thought to have a worldwide distribution but recent research ^[1] has restricted its range to coastal regions of the north-eastern Atlantic Ocean as far north as Iceland, the Mediterranean Sea and the Black Sea, with specimens from other regions assigned to different species.

Acartia clausi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Copepoda
Order:	Calanoida
Family:	Acartiidae
Genus:	Acartia
Species:	A. clausi
Binomial name
Acartia clausi Giesbrecht, 1889
Synonyms
Acartia clausii Giesbrecht, 1889

At just over 1 mm in length, this is a generally larger animal than its closest congeners. It can also be distinguished by the row of large spines at the rear margin of the body segment known as the metasome.