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Amphibalanus
acorn barnacle
Amphibalanus is a genus of acorn barnacles in the family Balanidae, established by Pitombo in 2004 to accommodate species formerly assigned to Balanus. The genus contains multiple species including the widespread and economically significant Amphibalanus amphitrite and A. improvisus. These barnacles are characterized by their conical calcareous shells, cemented base, and planktonic larval stages culminating in a settlement-competent cyprid stage. Several species have become established outside their native ranges as invasive biofouling organisms in ports and harbors worldwide.