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

The morphology of Ichthyophonus sp., a parasite of Mugil capito and Liza sa liens, was investigated by light and transmission electron microscopy. The most frequent stage found in the fish hosts was the multinucleate spore, th ough germinating stages, hyphae, and endospores were also found. Different development patterns were observed in the media assayed for in vitro cultur e. Optimal growth and development were obtained in Eagle's minimum essentia l medium (MEM) supplemented with 10% fetal bovine serum at pH 7. Ultrastruc tural features of multinucleate spores, both in the fish host and in cultur e, were a fibrillar thick wall and an electron-lucent matrix, with large gl ycogen granules, some electron-dense bodies, large vacuoles, lipid inclusio ns, and endoplasmic reticulum mainly appearing among the nuclei. Mitochondr ia with scarce tubulovesicular cristae were observed in the different stage s, mainly near the wall and the germinating sites. Condensed heterochromati n was rarely seen. A nucleus-associated organelle (NAO) was frequently obse rved, and dictyosome cisternae and vesicles appeared in its vicinity.