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

Abstract

We report here for the first time the karyotype of the Iberian imperial eagle <i>(Aquila adalberti).</i> 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 <i>A. adalberti</i> from <i>A. heliaca</i> 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 <i>Alu</i>I 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 <i>A. adalberti </i>and its most closely related species, <i>A. heliaca.</i>