Fig. 1: P. viburni male meiosis stages in wild-type (2n = 10 chromosomes) and B-carrying (2n = 10 + 1B chromosomes) individuals. | Heredity

Fig. 1: P. viburni male meiosis stages in wild-type (2n = 10 chromosomes) and B-carrying (2n = 10 + 1B chromosomes) individuals.

From: Chromatin state dynamics of autosomes and the B chromosome during spermatogenesis in Pseudococcus viburni

Fig. 1

A Representative images of spermatogenesis stages (Hoechst staining). a–e First meiotic division (equational). a Early prophase I: maternal chromosomes are relaxed, while paternal chromosomes are individualised. b Mid-prophase I: maternal chromosomes condense and individualise, paternal chromosomes form a dense cluster. c Prometaphase I: paternal chromosomes localise at the centre of the metaphase plate, surrounded by maternal chromosomes. d Metaphase I: sister chromatid separation. e Telophase I: chromosome arrangement remains the same as in metaphase I. f, g Second meiotic division (reductional). f Metaphase II: homologous chromosomes are distributed on either side of the metaphase plate according to their parental origin. g Telophase II: nuclei carrying paternal chromosomes (top left) and maternal chromosomes (bottom right). h–l Spermiogenesis. h Round spermatids with condensed paternal chromosomes. i Early elongation: 32 elongating spermatids, 32 round nuclei. j Mid-elongation: 32 elongating spermatids, 32 round nuclei. k Late elongation: 32 elongated spermatids, 32 round nuclei. l Sperm bundle formation and degradation (<32 round nuclei). Asterisks indicate somatic nuclei. B, D Schematic representation of meiotic divisions and the characteristic position of chromosomes in wild-type males (B) or in males carrying one B chromosome (D). Light grey: maternal chromosomes; dark grey: paternal chromosomes; yellow: B chromosome. C Representative images of meiotic stages in a male carrying one B chromosome, identified by a FISH probe targeting the PviSat16-172 satellite repeats (green); DNA is stained with DAPI (magenta). The B chromosome segregates with paternal chromosomes at the start of meiosis and later joins maternal chromosomes in prometaphase I. Metaphase I shows the equational division of B chromosome sister chromatids. The B chromosome remains associated with maternal chromosomes until the end of meiosis. Scale bars: 5 µm (A a–h and C); 10 µm (A i–l). MG Maternal genome, PG Paternal genome, B B chromosome.

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