Ultrastructure of the Host-Parasite Interface between Allomyces javanicus and Its Endoparasite Catenaria Allomycis

Abstract

The interface between the endoparasitic fungus, Caienaria allomycis, and its aquatic fungal host, Allomyces javanicus, is described from a developmental, ultrastructural study. The wall of the parasite interfaces with the cytoplasm of the host. As the parasite develops, host organelles show a progressive sequence of preferential associations with the parasite. During the round cell and spindle cell stages of the parasite, host endoplasmic reticulum (ER) proliferates and ensheathes the parasitic thallus. At later stages, host ER becomes organized into membranous labyrinths continuous with whorls of single cisternae, and host lipid globules cluster around the parasite. When parasitic sporangia are mature, the host cytoplasm begins to degenerate. Fragments of host ER cling to the surface of the parasite after most host membranes have vesiculated. The dynamic changes in the host-parasite interface are discussed in relationship to the obligate requirement of the parasite for nutrients supplied by the host.