Friday, September 20, 2019

Female Ambystoma Salamanders are Gene Thieves

It has been known for about a decade that an all-female species of Ambystoma salamanders were genetic thieves— mating with multiple males under the Ambystoma species and stealing copies of their genomes. The all-female lineage is suspected to be a mutation that occurred 5 to 6 million years ago when a pair of salamanders mated; with the mutation still persisting to this day. It has been recently discovered, however, that the female salamander does not just go around stealing genomes. They use the genetic material collected from males and incorporates all three genomes equally to pass down to her offspring, as well as "discarding" genes she does not need to use. This process is dubbed kleptogenesis (theft of genetic material), and the all-female Ambystoma species is the only animal on the planet performing this act.

Researchers from the University of Iowa were curious about how the female salamander chooses which genes to keep and which ones to throw away. The research team analyzed more than 3,000 genes from a single unisexual Ambystoma female that had three genomes (triploid) from different male Ambystoma species. About 72% of the male genes analyzed were equally expressed, meaning the female chose to use around the same number of genes from each male salamander species. Although the process of how the female salamander picks certain genes is still unknown, lead author Kyle McElroy theorizes that the genes are like a sports team. The sports team has equally competent players with no particular star athlete standing out. If someone gets injured, the competent team won't be affected by it because they are all on the same level. It is suspected that the female salamander doesn't decide which genes to keep individually, but has a balanced ratio of genes from the three different male species that work for her to create a successful hybrid.

I find this species of salamander to be very unique, especially since they are the only female species on the planet to take genes from several different male Ambystoma species. Normally offspring receive chromosomes from one female parent and one male parent, but the offspring for these female salamanders receive genetic traits from the mother and many different fathers. It is very interesting to see how the all-female Ambystoma species adapted to a mutation that happened millions of years ago and that they are still using kleptogenesis to this day.


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