Studies on Chilodonella cyprini and C. hexasticha (Protozoa, Ciliata) by scanning electron microscopy

Specimens of the kinetophragminophorid ciliates Chilodonella cyprini (Moroff, 1902) from goldfish (Carassius auratus) in Nova Scotia and Chilodonella hexasticha (Kiernik, 1909) from channel catfish (Ictalurus punctatus) in Arkansas were examined by scanning electron microscopy. They are round to foliate, ventrally flattened protozoa well suited for adherence to, and movement over, a flat host surface. Organelles including ventral ciliary rows, dorsal cilia, excretory pores, and a prominent cytopharynx are described. Dorsal surfaces of both species have a distinct reticulate pattern which represents a modification of the pellicle. Ventrolateral margins of C. cyprini contain rows of short cuticular proturberances not seen in C. hexasticha. Our specimens of the two species were distinguished by their total ventral ciliary row number (12–14 in C. hexasticha, 21 in C. cyprini). General morphology as revealed by scanning electron microscopy is compared with previous light microscopical observations. The taxonom...