Algal tumors in the Caribbean octocorallian Gorgonia ventalina

Tumor-like growths associated with necrosis in the Caribbean octocorallian, Gorgonia ventalina, contain an infesting filamentous green alga which is not detectable in normal, non-tumorous colonies. The infesting alga is identified here by the chromatographic resolution and spectrophometric characterization of pigments unique to the algal Order Siphonales. Similar algae commonly are found as endolithic, non-pathogenic and non-tumorigenic associates of many scleractinian species. The tumorigenic response in G. ventalina includes hyperplasia of the coral mesenchyme; this tissue secretes abnormal elements of endoskeletal collagen-like gorgonin, elaborated as a dense network of fine tubules which encapsulate but do not kill the infesting algal filaments.The infesting alga and host response described for G. ventalina differ from those we have observed in other Caribbean gorgonian species. The incidence of tumorigenic algal infestation in G. ventalina, in contrast to that seen in other species, is non-uniform. The incidence of these tumors may prove useful as an indicator of environmental stress, damage by predation, or other as yet unidentified ecological factors controlling growth, parasitic infestation and mortality in reef communities.