Opercularia articulata has been recorded as both free-living as a symbiont. The aim of this contribution is to present some geographical distribution, cytological, ecological, and symbiotic data from this ciliate, as a symbiont of crayfish. Procambarus (Austrocambarus) sp. were collected from Lagos de Montebello, Chiapas during two climatic seasons through a year. Some physico chemical data were obtained in order to infer if any relationship of the ciliates presence with the properties of the water is present. We found 150 zooids (cells) as epibionts on 95% of the crayfish, finding a seasonal variation regarding the ciliate density. Ciliates belong to genus Opercularia that are characterized by inhabiting low-quality water environments, considering them as biological indicators. As for geographical distribution, the European continent showed the highest number of records, while for Australia and Africa there are no records. [ABSTRACT FROM AUTHOR]