Redescription of Apocorophium acutum (Crustacea, Amphipoda, Corophiidae) with material from type locality and key of world Apocorophium species

Apocorophium acutum (Chevreux, 1908), the type species of the genus, was originally but only partially described by Chevreux with female specimens from Bônes (Algeria); male specimens were later described from Brittany (France). Since then, the species has been recorded in different places of the world, some of them questionable. Herein, the species is entirely redescribed with material from the type locality and Brittany, and additional material from Arcachon Bay is studied to provide biological data. The known geographical distribution of this species is summarized, and a world identification key of Apocorophium species is also given.