This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the first detailed chromosome map of the aardwolf, Texas A&M University researchers have discovered that, despite millions of years of separate evolution, the chromosomes of aardwolves, other hyenas and even domestic cats have remained remarkably similar. The aardwolf, a termite-eating mammal native to Africa, is the least-studied member of the hyena family.
Until now, the only chromosome information on the aardwolf was its chromosome count—40—which was discovered in the 1960s. The study, published in the Journal of Heredity, was led by Dr. Terje Raudsepp, a professor in the Department of Veterinary Integrative Biosciences at the Texas A&M College of Veterinary Medicine and Biomedical Sciences (VMBS), in collaboration with Twin Pine Conservation Institute (TPCI).
The new study provides the first detailed look at the species' karyotype and contributes to broader efforts to build chromosome-level references for mammals. So far, only about 1,200 of roughly 6,000 mammal species have detailed chromosome maps. "This chromosome-level study shows why adding more mammalian species is important," Raudsepp said.
"You never know when a species might become extinct." Although earlier studies have sequenced the aardwolf's genome, its DNA remains divided among roughly 5,600 fragments. By mapping the animal's chromosomes, the new study gives researchers a guide for putting those pieces in order. "Now that we have been able to compare the chromosomes of the aardwolf and spotted hyenas, there are specific differences to look for in a future genome sequence," said Mayra Mendoza, a doctoral student in Raudsepp's lab and a co-first author of the study.
To obtain the aardwolf's chromosomes, the team grew cells from a skin sample sent by TPCI and waited for them to divide—the only moment when chromosomes appear as distinct rods under a microscope. Using a staining technique that highlights each chromosome with a unique, barcode-like pattern of light and dark stripes, the team compared the structure of aardwolf chromosomes with those of spotted hyenas, the aardwolf's close relative. Side by side, the two species' chromosomes looked nearly identical.
"The center aligns the same way, and the banding pattern is unchanged—only three pairs show something different," Mendoza said. "Later, we confirmed that these regions may be unique to the aardwolf or perhaps to another hyena lineage." The stability makes sense, as aardwolves and spotted hyenas diverged only about 10.6 to 11.6 million years ago, a relatively short span in evolutionary terms. The surprise, though, came when the team compared aardwolves with domestic cats using a chromosome-painting technique, which allows researchers to compare chromosomes at the DNA sequence level.
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