Karyotypes and chromosomal locations of C-banded heterochromatin and silver-positive nucleolus organizer regions (Ag-NORs) were studied in two anemonefish species, Amphiprion ocellaris and A. ephippium. These two species had the same diploid chromosome number of 48 and the same fundamental number (NF) of 86. As a remarkable feature found in conventional stained chromosomes, A. ocellaris had distinct secondary constrictions (SCs) in the pericentromeric regions in the long arms of a pair of the large submetacentric chromosomes. The Ag-NOR staining revealed that these SCs were Ag-NORs. This interstitial type of NOR-location was first case in anemonefish species. On the other hand, Ag-NORs in A. ephippium were observed in the terminal regions of the short arms of an acrocentric pair as well as those in the other species already studied. C-banding pattern showed species-specific features and the Ag-NORs were C-band positive in both species. On the basis of the molecular phylogeny and the chromosomal location of NORs, it is inferred that the terminal type of NOR-location is original in anemonefish evolution and the interstitial type of NOR-location in A. ocellaris has been changed from the terminal type by the occurrence of pericentric inversion including NORs.

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Rumex acetosa (Polygonaceae) originally distributed in temperate Eurasia is a dioecious dicotyledon having sex chromosomes XX in female and XY₁Y₂ in male plants. In this species, X chromosome rearrangements were reported by Wilby and Parker (1988) and Iwatsubo (2016). This report describes a newly discovered male plant having an X chromosome showing an unusual form. The ordinary X chromosome in R. acetosa has two arms of almost equal length with a 1.03 arm ratio (long arm/short arm), whereas the X chromosome found in this male plant showed a 1.67 arm ratio. In meiotic chromosome pairing, the end of the short arm of this aberrant X chromosome was paired with the Y₁ chromosome, and the end of the long arm was paired with the Y₂ chromosome, suggesting that this X chromosome arose by pericentric inversion.

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