Figure 1

Intraspecific aggression in Anthopleura elegantissima polyps. Acrorhagi (A) are visible on the polyp in the center and the polyp to the left. A highly extended acrorhagus of the central polyp (arrow) is being applied to the column of the polyp on the left. Unlike the filiform tentacles, acrorhagi are opaque and rounded at the tip, even in extension. The polyp on the right has contracted in response to its encounter with the polyp in the center; its column is covered with mucus and several acrorhagial peels (P) from the central polyp.