The morphology of Ichthyophonus sp. in their mugilid hosts (Pisces: Teleostei) and following cultivation in vitro. A light and electron microscopy study.

Abstract

The morphology of Ichthyophonus sp., a parasite of Mugil capito and Liza saliens, was investigated by light and transmission electron microscopy. The most frequent stage found in the fish hosts was the multinucleate spore, though germinating stages, hyphae, and endospores were also found. Different development patterns were observed in the media assayed for in vitro culture. Optimal growth and development were obtained in Eagle's minimum essential medium (MEM) supplemented with 10% fetal bovine serum at pH 7. Ultrastructural features of multinucleate spores, both in the fish host and in culture, were a fibrillar thick wall and an electron-lucent matrix, with large glycogen granules, some electron-dense bodies, large vacuoles, lipid inclusions, and endoplasmic reticulum mainly appearing among the nuclei. Mitochondria with scarce tubulovesicular cristae were observed in the different stages, mainly near the wall and the germinating sites. Condensed heterochromatin was rarely seen. A nucleus-associated organelle (NAO) was frequently observed, and dictyosome cisternae and vesicles appeared in its vicinity.