Résumé
In a Japanese hagfish, Eptatretus burgeri, 16 chromosomes (E-chromosomes), corresponding to 20.9% of the total germline genome DNA, are expelled from presumptive somatic cells (2n=52). To date, at least 11 eliminated repetitive DNA families amplified selectively in the germline genome have been identified from this species, and FISH analysis showed that almost all repetitive families such as EEEb1 (Eliminated Element of E. burgeri 1) were selectively detected on all E-chromosomes. On the other hand, EEEo1 (Eliminated Element of E. okinoseanus 1) and EEEo2 were not detected in E-chromosomes. The present study demonstrated that the signals as the pinpoint were detected on the interstitial region of the identical bivalent EEEb1-negative chromosome (non-Echromosome) in the spermatocytes, and neither EEEo1 nor EEEo2 signals were observed in somatic cells. Thus, this is the first report showing the internal deletion of eliminated repetitive DNA families from non-E-chromosomes in this species.