EPIBIOTIC BACTERIA ON SEVERAL CILIATES FROM MARINE-SEDIMENTS

Bacterial epibionts were observed on the surface of the marine sedimen t ciliate Geleia fossata. Rod-shaped bacteria, from 2-10 x 10(3) per c iliate, were universally positioned in ciliated grooves, in apparent s patial association with dikinetids. SEM and TEM examination of the cil iates confirmed that a tight affiliation exists between the epibiotic bacteria and ciliate cortex ultrastructures. These observations, as we ll as the distinct bacterial distribution pattern over ciliate surface , suggest that there is a close epibiont/host physiological integratio n. Epibiotic bacteria were also observed on the surfaces of other sedi ment ciliates from the genera Loxophyllum, Tracheloraphis, Geleia, Par aspathidium, and Cyclidium. These findings indicate that the bacterial /protozoa associations are widespread in the marine benthic environmen t. The potential benefits for both epibionts and their hosts are discu ssed.