Four zoospore subtypes in the Rhizophlyctis–Karlingia complex (Chytridiomycetes)

Abstract

Four subtypes of zoospores are described, with the use of the transmission electron microscope, for chytridiomycetous fungi that can be classified with light microscopy in the Rhizophlyctis–Karlingia complex. Subtype A has ribosomes dispersed throughout the cytoplasm; a long fibrillar rhizoplast; mitochondria and microbody closely associated with the rhizoplast; and numerous lipid globules that have occasional association with microbody. Subtype B has ribosomes concentrated into the center of the zoospore, and these are partially surrounded by endoplasmic reticulum; a short fibrillar rhizoplast; microbody associated with a basal lip of the nucleus; mitochondria that surround the rhizoplast; and numerous lipid globules that have occasional association with microbody. Subtype C has ribosomes concentrated (as in subtype B); several mitochondria interwound with microbody in the basal area between the kinetosome and nucleus; and numerous lipid globules that have occasional association with microbody. Subtype D has ribosomes concentrated (as in subtypes B and C); a long heel-like segment of the nucleus that extends to a point adjacent to the kinetosome; a close association between the nuclear heel, microbody, and mitochondria; and a large lipid globule which has close association with microbody and is partially surrounded by endoplasmic reticulum. None of the subtypes contain cytoplasmic microtubules. The taxonomic significance of the cytology is discussed. It is concluded that these subtypes of zoospores are more closely related to the Spizellomycetales than the Chytridiales.