Figure 4.
Unusual dinoflagellate chromosome structure. (A) Brightfield picture of a formaldehyde–fixed Karlodinium veneficum cell. (B) Nucleus of above cell stained with DAPI; note the high number and condensed appearance of the chromosomes. (C1) Electron micrograph of a section of K. veneficum cell fixed with glutaraldehyde and stained with osmium tetroxide. Chromosomes have a fluffy, cotton candy-like appearance (C2). (D1) A cell from the same culture but high-pressure frozen and freeze substituted with osmium instead. Chromosomes are highly electron dense and compact with a banded pattern (D2). The differences in appearance of the nuclei and chromosomes in (C1,C2) and (D1,D2) highlight how diverse fixation protocols produce very disparate results and that interpretation based solely on such pictures is likely not informative.