GUANOPHOROMA IN THE RED-SEA SILVERSIDE ATHERINOMORUS-LACUNOSUS (PERCIFORMES, ATHERINIDAE)

The occurrence of a spontaneous tumor affecting the guanophore iridocy tes of the Red Sea silverside Atherinomorus lacunosus is described. Th e tumoral mass consisted mainly of yellowish, light-reflecting guanine platelets. The tumor infiltrated the fibers of the underlying muscle tissue, growing in whorls around them. A delicate network of capillari es provided the tumor with a blood supply. No viral particles were obs erved. This rare form of tumor is the first of this kind reported in a feral fish from the Red Sea.