Natures wonders: snake with too many chromosomes (Introduction)

by David Turell , Sunday, April 06, 2025, 19:03 (3 days ago) @ David Turell

Has three sets:

https://www.sciencedaily.com/releases/2025/04/250402181317.htm

"The flowerpot snake, one of the world's smallest snakes, has some unusual distinctions. Also known as the Brahminy blind snake, it's the only known snake species with three sets of chromosomes instead of two -- and it can reproduce without a mate.

"By analyzing the flowerpot snake's unique genome, scientists at The University of Texas at Arlington are uncovering how the tiny reptile repairs its DNA and prevents harmful mutations. The findings, published recently in the journal Science Advances, provides valuable insights into genetic repair mechanisms that could deepen our understanding of human gene evolution.

"'This DNA repair and replication activity supports a fascinating mechanism called premeiotic endoreplication, a process through which the snake duplicates its chromosomes before dividing them, sidestepping the need for the typical pairing of chromosomes seen in sexual reproduction," said Matthew Fujita, a professor of biology at UTA and a co-author on the paper along with researchers from China and Myanmar. "This mechanism allows the snake to produce offspring that are exact genetic clones of itself."

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"Using advanced genomic technology, the research team discovered that the flowerpot snake, native to Africa and Asia, has 40 chromosomes, organized into three subgenomes. These subgenomes formed through complex genetic events, including chromosome fusion in ancestral species. The researchers hypothesize that this genetic structure enables the snake to reproduce without needing sperm from a male partner.

"One major question the scientists explored was whether this reproductive strategy comes with evolutionary drawbacks. Asexual species typically struggle because they lack genetic shuffling, which helps eliminate harmful mutations over time. However, the flowerpot snake appears to have developed a way to counteract this risk. The researchers believe its slow but steady evolutionary pace helps limit the accumulation of harmful mutations.

"They also examined how genetic variations across different flowerpot snake populations suggest chromosome exchanges between the subgenomes. These exchanges appear to balance genetic diversity and stability -- maintaining enough variation for adaptation while preventing incompatibilities that could disrupt reproduction.

"'The study also revealed something unexpected -- many of the flowerpot snake's immune-related and sexually selected genes, such as those involved in sperm development, have lost their functions," Fujita said. "This finding provides key insights into how reproduction without a mate works in reptiles, but it also reshapes some of our long-held views about the limitations of asexual species. Rather than being an evolutionary 'dead end' as researchers have thought, the flowerpot snake shows how nature can innovate and adapt in extraordinary ways.'"

Comment: this may be a weird dead end. Providing "exact genetic clones" does not advance evolution of this species. That different species share chromosomes does help in providing variations.