Banding differences between tiger salamander and axolotl chromosomes

Area of Science:

• * Amphibian genetics and comparative genomics.
• * Cytogenetics and chromosome analysis.

Background:

• * Axolotl (Ambystoma mexicanum) and tiger salamander (Ambystoma tigrinum) are closely related species.
• * Understanding their chromosomal differences can illuminate evolutionary divergence.

Purpose of the Study:

• * To compare the Hoechst 33258 - Giemsa banding patterns of prophase chromosomes between axolotl and tiger salamander.
• * To identify chromosomal similarities and differences, including deletions, translocations, and inversions.

Main Methods:

• * Analysis of prophase chromosomes using Hoechst 33258 and Giemsa staining techniques.
• * Detailed comparison of banding patterns across the haploid chromosome sets of both species.

Main Results:

• * Axolotl exhibited approximately 369 bands per haploid set; tiger salamander showed about 344 bands.
• * Chromosome 3 displayed a constant nucleolar organizer region (NOR) constriction.
• * Sex chromosomes ZW were identified, with females being heterogametic. Chromosome 9 in axolotl and 10 chromosomes in tiger salamanders showed terminal or internal deletions. Chromosomes 1, 6, 11, and Z showed indistinguishable banding patterns.

Conclusions:

• * Chromosomal banding patterns reveal species-specific deletions in axolotl and tiger salamanders.
• * Significant conservation exists in banding patterns for several chromosomes and sex determinants between the two species.
• * No evidence of translocations or inversions suggests limited large-scale chromosomal rearrangements since their evolutionary separation.