On the highest chromosome number in mammals

Area of Science:

• Cytogenetics
• Mammalian Genetics
• Zoology

Background:

• The Neotropical Cricetidae family includes diverse rodent species with varying karyotypes.
• Understanding chromosome evolution in rare species like Ichthyomys pittieri is crucial for evolutionary biology.
• Previous studies reported a high diploid number in Anotomys leander, another Neotropical cricetid.

Purpose of the Study:

• To analyze the mitotic and meiotic chromosomes of Ichthyomys pittieri.
• To determine the diploid chromosome number and karyotype of I. pittieri.
• To compare the karyology of I. pittieri with related species and summarize karyological relationships within Neotropical Cricetidae.

Main Methods:

• Conventional staining techniques for chromosome analysis.
• Banding techniques (e.g., G-banding, C-banding) for detailed chromosome structure.
• Microscopic examination of mitotic and meiotic cells.

Main Results:

• Ichthyomys pittieri exhibits a diploid chromosome number of 2n = 92.
• This represents the highest diploid chromosome number recorded for any mammal species.
• The karyotype of I. pittieri was compared with Anotomys leander, also reported with 2n = 92 chromosomes.

Conclusions:

• The exceptionally high chromosome number in I. pittieri is hypothesized to result from recurrent centric fissions.
• The findings contribute to understanding chromosome evolution and diversification within the Cricetinae subfamily.
• Karyological relationships within the Neotropical Cricetidae are elucidated, highlighting conserved and divergent chromosomal patterns.