The karyotype of the Iberian imperial eagle (Aquila adalberti) analyzed by classical and DNA replication banding

Abstract

We report here for the first time the karyotype of the Iberian imperial eagle (Aquila adalberti). All eagles examined had a diploid number of 82 chromosomes and a greater number of microchromosomes (12 pairs) than has been found in all other species of the Accipitridae family. This karyotypic evidence corroborates the recent separation of A. adalberti from A. heliaca on the basis of molecular data. RB-FPG banding induced a specific banding pattern that allowed us to identify homologous chromosome pairs and revealed features about late and early replicating regions. Several chromosome banding techniques (C-, CMA₃-, and restriction endonuclease banding and silver staining) were used to characterize the karyotype more accurately. Two GC-rich, late-replicating heterochromatin regions were found in the W chromosome. These regions are AluI resistant and can be used for sex determination in this species. All microchromosomes were heterochromatic, GC rich, and late replicating. Silver staining revealed active nucleolus organizing regions on a pair of microchromosomes that were entirely heterochromatic and stained intensely after CMA₃-banding. Different chromosome rearrangements are discussed in order to establish the phylogenetic relationship between A. adalberti and its most closely related species, A. heliaca.