CYTOLOGICAL EXAMINATION OF SYMBIONT LOSS IN A BENTHIC FORAMINIFERA, AMPHISTEGINA-GIBBOSA

Since September 1991, A. gibbosa populations in the Florida Keys have been afflicted by an unidentified disease. Symptoms include symbiont-l oss (ranging from slight mottling to complete bleaching), shell breaka ge, shell-surface lesions that permit boring and epiphytic microorgani sms to invade living specimens, deformed tests, and reproductive dysfu nction. Cytological examination of mottled and bleached specimens reve aled membrane disintegration, symbiont digestion, lysosomes adjacent t o symbionts, enlarged vacuoles in the cytoplasm, few mitochondria or o ther organelles, and granulation of the cytoplasm. Normal-appearing sp ecimens from damaged populations also have granulated cytoplasm and ab normally abundant lysosomes in the vicinity of symbionts, indicating e arly stages of the disease.