Photo Credit: via Reuters

An all-female freshwater fish species called the Amazon molly inhabits rivers and creeks along the Texas-Mexico border and is living proof that sexual reproduction may well be massively over-rated. 

According to Reuters, when deciphering the species genome scientists discovered that it has none of the genetic flaws that they expected. This included an accumulation of harmful mutations and a lack of genetic diversity. 

Instead, they found that the Amazon molly boasts a tough genetic makeup that makes it equally fit, or even more so, than fish using sexual reproduction in which both maternal and paternal genes are passed along to offspring. 

“The Amazon molly is doing quite well,” explained biologist Manfred Schartly of the University of Wuerzburg in Germany. “Unexpectedly, we did not find the signs of genomic decay as predicted.”

The fish reproduces using a strategy in which a female’s egg cell develops into a baby without being fertilized by a male’s sperm cell. 

“The Amazon molly female produces clones of itself by duping a male of a closely related species to mate with her. The asexual mode of reproduction termed gynogenesis requires the female to mate with a male but none of the male’s genome is passed to the offspring,” said geneticist Wesley Warren of the McDonnell Genome Institute at Washington State University in St. Louis. 

The egg cells are activated to develop into an embryo by a sperm cell that degenerates without fusing with the egg’s nucleus. 

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