opercularia (ciliate) opercularia (ciliate) opercularia is a genus of freshwater, colonial, sessiline peritrich ciliates. as consumers of free bacteria in the water, several species of opercularia serve as important indicator organisms in the study of wastewater treatment. operculariids can be distinguished from other sessile peritrichs (many of which share very similar body plans) by their prominent, non-contractile stalk; peristome without lip; and elongate, horseshoe-shaped macronucleus. opercularia scientific classification domain: eukaryota clade: diaphoretickes clade: sar clade: alveolata phylum: ciliophora class: oligohymenophorea order: sessilida family: operculariidae genus: operculariagoldfuss, 1820 etymology the name opercularia comes from the latin opercularis, which means covered (with a lid). this is in reference to their lid-like peristomal disk. selected species selected species include: opercularia allensi stockes, 1887 opercularia coarctata claparede & lachmann, 1858 opercularia cylindrata wrzesniowski, 1870 opercularia longigula nenninger, 1948 opercularia minima kahl, 1935 opercularia nutans (ehrenberg, 1831) stein, 1854 opercularia stenostoma stein-d'udekem