Abstract
The karyotype of the finless eel Dalophis imberbis was investigated by conventional (C and replication banding, CMA3 fluorescence) and molecular (FISH with 45S rDNA probe) techniques. The diploid chromosome number was 2n = 46 and the karyotype consisted of four pairs of meta-submetacentric and 18 pairs of subtelo-acrocentric autosomes and a pair of sex chromosomes heteromorphic in females, composed by a large subtelocentric Z, and a medium sized acrocentric W chromosome; in males this pair was composed by two large subtelocentric ZZ chromosomes. Multiple NORs have been localized by FISH and have been found to be CMA3 positive; one of the NORs was located on the W chromosome and it was found transcriptionally active by silver staining. The Z chromosome contained distinct intercalar C-positive heterochromatin and W was almost completely heterochromatic. Our report contributes to the knowledge to the cytotaxonomy of Anguilliformes where differentiated sex chromosomes are reported in about a quarter of the species: both male and female heterogamety as well as a multiple chromosome system have been reported. Moreover, this is the first anguilliform species in which multiple NORs have been reported.
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Acknowledgements
The authors wish to thank Prof. Ugo Laudani for helpful suggestions. This research was supported by Italian Ministry of Instruction, University and Research (MIUR) Grant No. DM219-22-12-05, National Relevant Interest Research Projects (PRIN), 2005.
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Salvadori, S., Coluccia, E., Cannas, R. et al. A ZZ–ZW sex chromosome system in the finless eel Dalophis imberbis (Anguilliformes, Ophichtidae). Genetica 135, 283–288 (2009). https://doi.org/10.1007/s10709-008-9276-4
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DOI: https://doi.org/10.1007/s10709-008-9276-4