Myelin-like ‘artifacts’ in the zoospores of Blastocladiella emersonii

Abstract

Myelin-like figures with repeating lines of 5·0–5·5 nm frequently appear in the nucleus and at the boundary between it and the nuclear cap in zoospores of Blastocladiella emersonii Cantino & Hyatt fixed in glutaraldehyde and immediately post-fixed in osmium tetroxide. The incidence of such profiles is greatly reduced when glutaraldehyde-fixed spores are washed for 24 h before they are post-fixed with osmium tetroxide, and they do not appear when spores are prepared in other combinations of fixatives. Myelin-like figures may reflect underlying membrane alterations that occur when zoospores have been triggered to encyst. It was briefly mentioned recently (Truesdell & Cantino, 1971) that within the first few minutes after zoospore suspensions of Blastocladiella emersonii have been triggered to encyst, myelin-like figures occur in the region between the nuclear cap and the nucleus, and in the nucleus itself, if the zoospores are fixed with glutaraldehyde and post-fixed with osmium tetroxide. Such myeloid bodies show up frequently, however, only if the post-fixation with osmium is done immediately. The purpose of this report is to illustrate the nature of such myelin-like profiles.