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Salamander found to reproduce using the sperm of at least three males

June 12 (UPI) — Why pass along the genes of a single mate when you can impart one’s offspring with DNA from three fathers? Such is the unique reproductive strategy used by hybrid all-female populations of ambystomatid salamanders.

When biologists from the University of Iowa sequenced the genome of all-female, or unisexual, salamanders, they found equal portions of DNA from three different species, Ambystoma laterale, Ambystoma texanum and Ambystoma tigrinum.

“We’re hypothesizing the successful individuals have balanced gene expression,” Maurine Neiman, a professor of biology at Iowa, said in a news release. “This balance might have been a prerequisite for the emergence and continued success of this particular hybrid lineage.”

Researchers believe all-female salamanders employ a reproductive technique known as kleptogenesis, whereby sex is used not to directly fertilize eggs but to steal another’s genetic material. The method has allowed the hybrid, a native to North America, to maintain an all-female lineage for more than six million years.

All-female ambystomatid salamanders boast a triploid genome, a trio of chromosome. When scientists analyzed a specimen’s triple genomes in the lab, they found the majority of genes stolen from Ambystoma laterale, Ambystoma texanum and Ambystoma tigrinum are expressed equally.

“It’s mostly balanced. The three genomes are mostly being expressed equally in this hybrid,” said Kyle McElroy, a graduate student in Neiman’s lab. “What we’d like to find out is how the choosing and using occurs, and how these genes from different sexual salamander species come together to make a successful hybrid.”

Scientists suggest the strategy for structuring a successful triploid might be similar to filling-out a well-balanced roster on a sports team — relying on a plethora of above-average performers instead of supplementing a superstar with scrubs.

“If you have a team that’s unbalanced and loses a top player, you won’t win,” said McElroy. “But if every player is equal, then you don’t lose as much.”

The findings — detailed in the journal Genome Biology and Evolution — suggest the salamander balanced approach relies on the law of averages. By selecting evenly from each genomic contributor, the all-female salamander covers all her bases, so to speak.

“It would be difficult to maintain without balance,” McElroy said, “and that may be the key to this hybrid’s success.”

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