Figure 1

(a–c) Polytene chromosomes of Schwenkfeldina sp. (a) Orcein staining photographed under bright field allows chromosome visualisation but not extrachromosomal structures of interest to this work. (b,c) Phase contrast images showing two morphological aspects often observed in the nuclear entities of this species. The arrows point to some examples of structures, either disconnected or attached to the chromosomes, that were eventually identified as micronucleoli on the basis of in situ hybridisation results. (b) Nucleolar bodies displaying sharp edges and exhibiting some internal structure and (c) micronucleoli with less sharp edges and apparently devoid of internal structure. Bar = 15 µm.