The Amazon Molly's Ability to Clone Itself

Director of Texas State’s Xiphophorus Genetic Stock Center, Dr. Ron Walter, along with his colleague Dr. Yuan Lu, are contributing authors to an article published February 12 in the Nature research journal Nature Ecology & Evolution.

The article lays out findings from research funded by the National Institutes of Health on an unusual fish species, the Amazon molly, which reproduces asexually and has been doing so for 100,000 to 200,000 years, quite an anomaly in the natural world.

Texas A&M University Faculty Fellow Dr. Manfred Schartl (University of Wuerzburg, Germany), who led the team of international researchers which includes Walter and Lu, explained the Amazon molly’s unusual reproductive process like this on the Texas A&M Today website: “In essence, mollies repeatedly clone themselves by duping the male fish of another species to waste their germplasm,” Schartl says. “This reminds one of the tribe of female warriors in the Greek mythology, from which their name is derived.” In other words, while the female species does need exposure to male sperm of a related molly species, that sperm only activates female egg production, with no DNA contribution to the offspring.

Typically, in a species producing asexually, the genes would eventually decay as a result of lack of diversity. This study looks at why that is not the case with the Amazon molly. As Schartl explains, “Our findings suggest that the molly’s thriving existence can be explained by the fact that the fish has a hardy genetic makeup that is often rare in nature and gives the animals some survival benefits.”

Dr. Lu, in the laboratory of Dr. Walter at Texas State University (Department of Chemistry & Biochemistry), performed analyses looking at allele specific gene expression in the asexual Amazon molly (Poecilia formosa), a species derived from ancient hybridization of the sexually reproducing species Poecilia latipinna and Poecilia mexicana.  Dr. Lu compared alleles (i.e. genes) from these two extant species with a set of genes produced by the Amazon molly, clearly identifying the molly’s genes as being derived from one or the other ancient hybrid parental species.  Then he investigated whether genes in the Amazon molly from one parent showed favor for expression, relative to genes from the second parent species. Surprisingly, the alleles showed no bias based on parental species origin, and this supports the idea that the Amazon molly has not undergone genetic decay, as predicted for asexual reproduction, and instead shows remarkable fitness as an asexual vertebrate.

The Amazon molly can be found in creeks and rivers along the Texas-Mexico border.