Ultrastructure of Kochiomyces and Triparticalcar zoospores (Spizellomycetales, Chytridiomycetes)

Abstract

Kochiomyces and Triparticalcar are recently described genera. Each has unique ultrastructural characteristics in its zoospore. They are classified in the new order Spizellomycetales, in the class Chytridiomycetes. The zoospores of Kochiomyces have a posteriorly positioned nucleus which is ensheathed by microtubules. These microtubules originate from a compound spur on one side of the kinetosome. Microbodies, and one to five mitochondria surround the nucleus. Lipid globules occur in the anterior but these are not associated with microbodies. The Kochiomyces zoospore resembles a primitive blastocladiaceous zoospore which suggests a phylogenetic connection. The zoospores of Triparticalcar have an anteriorly positioned nucleus anchored to the kinetosome by microtubules and a spurlike structure. The spur is 0.8–2.5 μm long and tripartite in cross section. Microbodies are closely associated with lipid globules in the anterior and center of the zoospore. Mitochondria occur not only in the posterior, but also in the center of the zoospore where they often lie close to lipid globules and microbodies.