Spontaneous aberrations in lampbrush chromosome XI from a specimen of Triturus vulgaris meridionalis (Amphibia, Urodela)

Abstract

Comparison between the standard maps of the Triturus vulgaris meridionaiis lampbrush chromosomes and the lampbrush karyotype of an adult female (♀-IX) belonging to the same subspecies revealed the occurrence of two different chromosomal rearrangements in one bivalent of ♀-IX: lampbrush chromosome XI showed, in fact, a paracentric inversion in one homologue and an intercalary deletion in the other one. The same inversion was detected in all oocytes, whereas the deletion was present only in some of them. These rearrangements appeared in a region of the homologues in which chiasmata are not usually formed. The specimen, freshly collected from nature, appeared phenotypically normal and possessed well-developed ovaries. The occurrence of the heterozygous inversion in all oocytes suggests that very likely it has been transmitted to ♀-IX from one of the parents; the occurrence of the deletion in only a few oocytes indicates that it might arise at meiotic prophase I because of difficulties in pairing brought about by the presence of the inversion.