Acanthurus tractus Poey, 1860, a valid western Atlantic species of surgeonfish (Teleostei, Acanthuridae), distinct from Acanthurus bahianus Castelnau, 1855

Abstract

The ocean surgeonfish, Acanthurus bahianus, has been historically recorded from Bermuda and Massachusetts to southern Brazil and the islands of the central Atlantic. We have found that individuals in the southwestern and central Atlantic consistently have a posterior bright yellow margin on the caudal fin and an orange/red margin on the dorsal fin. This coloration is different from the characteristic white/blue fin margins on individuals from the northwestern Atlantic. In addition, there is a clear genetic distinction (d= 2.4% mtDNA, CytB) between these two lineages. With the corroborating coloration and genetic differences, we suggest that these two lineages represent distinct species. The South Atlantic species retains the name of A. bahianus and we propose to resurrect A. tractus (Poey 1860) as the valid name for the northwestern Atlantic species.