The morphology of Protoopalina pomacantha, n. sp., symbiont in the rectum of the Angelfishes, Pomacanthus zonipectus and Holacanthus passer. A light, scanning electron and transmission electron microscopic study

Protoopalina pomacantha n. sp. were discovered with fecal debris from the large hind gut chamber (rectum) of the Angelfishes, Pomacanthus zonipectus, and Holacanthus passer, collected from the Sea of Cortez near La Gaviota Island, Mexico. To describe this species, specimens from each host were studied with both light and electron microscopy. It is generally similar to other fish inhabiting protoopalines. The body is curved, contains a small anterior falx, and a pointed posterior end-barren of flagella. It has desmose fibrils interconnecting kinetosomes and electron dense substance within kinetosomes. The form of it's somatic kinetosomal desmose is similar to at least one species of the genus, Protoopalina, but differs from several. The falx kinetosomal and desmose ultrastructure is similar to several opalinids. This is judged to be a new species based on its host, components within the kinetosomal lumen, and desmose structures. Bacterial ectosymbionts are often found attached, in shallow pits, within a kinety and between flagella.