Summary
The ultrastructure of trophic stage (plasmodium), spore and changes in fine structure during morphogenesis of the spore were studied by electron microscopy in two representatives of the genusSphaeromyxa. Plasmodium has a highly differentiated structure; there is an outer layer of homogeneous plasm, the endoplasm consisting of a vacuolated mass in which “float” generative cells and sporoblasts in different degree of development. Generative cells have well developed pseudopodia. Sporoblasts arise from the union of two cells, out of which the inner one forms all cells of the spore, the outer one has only an enveloping function. Polar capsule develops in a way identical with other myxosporidia; the wide filament, however, has a longitudinally folded structure and is located within the capsule in two loose loops. The mitochondria of an early sporoblast are characterized by a high content of DNA. The identity of polar capsule development with the nematocyst morphogenesis is too conspicuous to be taken for a mere convergence. Studies on ultrastructure give no evidence for a protozoan character of myxosporidia; together with other findings, they are in favor of the nonprotozoan nature of this group of organisms.
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The essential part of this work was carried out in the Department of Biology, University of Illinois at Chicago Circle, where this study was aided by a grant from the National Science Foundation (NSF GB-2800) to Dr.J. Corliss. The author is also indebted to Dr.R. Fernald, University of Washington, for the use of all facilities at the Friday Harbour Laboratories of the University of Washington.
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Lom, J. Notes on the ultrastructure and sporoblast development in fish parasitizing myxosporidian of the genusSphaeromyxa . Z.Zellforsch 97, 416–437 (1969). https://doi.org/10.1007/BF00968848
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DOI: https://doi.org/10.1007/BF00968848