Comparison of P. ridibundus lampbrush chromosomes F (a, b), I (e, f), K (i, j), L (m, n) and P. lessonae lampbrush chromosomes F (c, d), K (g, h), J (k, l) and L (o, p, q). Phase contrast micrographs (a, c, e, g, i, k, m, o) and immunofluorescent staining with antibodies against snRNA (b, d, f, h, j, l, n, q) and coilin (p). Chromosomes are counterstained with DAPI. Arrows indicate the most conspicuous marker structures on lampbrush chromosomes, arrowheads show centromeres. Nu – extrachromosomal nucleoli. Scale bars = 10 μm.