Isozoanthus primnoidus, a new species of zoanthid (Cnidaria: Zoantharia) associated with the gorgonian Callogorgia verticillata (Cnidaria: Alcyonacea)

Abstract Carreiro-Silva, M., Braga-Henriques, A., Sampaio, I., de Matos, V., Porteiro, F. M., and Ocaña, O. 2011. Isozoanthus primnoidus, a new species of zoanthid (Cnidaria: Zoantharia) associated with the gorgonian Callogorgia verticillata (Cnidaria: Alcyonacea). – ICES Journal of Marine Science, 68: 408–415. In the Azores, Northeast Atlantic, an undescribed epizoan zoanthid is often found in association with the cold-water gorgonian Callogorgia verticillata at 110–800 m depth. This zoanthid was identified as a new species, Isozoanthus primnoidus sp. nov., based on morphological and anatomical characters of the polyps and type of cnidae. The distinguishing features of I. primnoidus are coenenchyme, column, and oral disc light brown, with short, translucent tentacles. Contracted polyps have column diameter up to 3 mm and height up to 2 mm. Ectoderm and outer mesogloea are densely encrusted with mineral particles and gorgonian sclerites. Capitulum bears a maximum of 14 distinctive ridges. Isozoanthus primnoidus was associated with 17% of C. verticillata colonies studied, and covered 14 ± 5% of the gorgonian colony. There was strong evidence of a parasitic relationship whereby I. primoidus progressively eliminates gorgonian tissue and uses the gorgonian axis for structure and support, and sclerites for protection.