Karyotypes and nuclear DNA contents of
Pseudolabrus eoethinus and
P. sieboldi were studied. Until a recent revision, the two species had been consid-ered a single species (
Pseudolabrus japonicus), although two clearly distinct kary-otypes had been reported on several occasions. The karyotype of
P. eoethinus was confirmed as 2M+2SM+44ST-A (2n=48, NF=52) and that of
P. sieboldi, as 20M+8SM+14ST-A (2n=42, NF=70). Nuclear DNA content in the two
Pseudolabrus species and 4 other labrid species from Japan was measured by flow cytometry, and provisionally expressed relative to that of a puffer fish,
Canthigaster rivulata, used as an internal standard. The relative nuclear DNA content of
P. eoethinus was 2.91±0.03 (n=5), that of
P. sieboldi being 3.00±0.05 (n=6). Al-though the two values differed significantly (Mann-Whitney
U test, P=0.01, U
cal=0.5), the very small difference between them (average value of latter 103% of former) together with karyotype comparisons suggested that both pericentric inver-sions and Robertsonian fusion had played a major role in the establishment of the more derived karyotype of
P sieboldi.
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