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 The Amazon Molly 

SOURCES

Heubel, Katja. “Population Ecology and Sexual Preferences in the Mating Complex of the Unisexual Amazon Molly Poecilia Formosa (GIRARD, 1859) .” Ludwigsburg, Germany, 2004.

Sperm is needed for to trigger the start of reproduction, but the sperm does not contribute to the genetic makeup of the offspring. Asexual lineages should go extinct after approximately 10.000 – 100.000 generations (Lynch & Gabriel 1990), but the amazon mollies have persisted through many more generations. Pros of reproducing asexually- only females are reproduced, so all offspring can reproduce. This results in more offspring in the population. Cons of reproducing asexually, the species will accumulate more mutations with each generation that can not be reversed. This is due to the lack of recombination and is called muller's ratchet.

Amazon-Molly-Genome-Research. “The Amazon Molly's Ability to Clone Itself.” Office of Research and Sponsored Programs : Texas State University, Texas State University, 9 Jan. 2019, www.txstate.edu/research/story-archive/2018-stories/amazon-molly-genome-research.html.

The Amazon Molly fish, Poecilia formosa, has been reproducing asexually for 100,000-200,000 years. Amazon molly fish are found in creeks and streams around the Texas-Mexico border.

Caspermeyer, Joe, and Jim Dryden. “Survival of All-Female Fish Species Points to Its DNA.” ASU, Warren WC, 12 Feb. 2018, biodesign.asu.edu/news/survival-all-female-fish-species-points-its-dna.

The Amazon Molly species was created when the Atlantic molly sexually reproduced with a Sailfin molly. Since then there has been about 500,000 generations of Amazon mollies. Amazon molly is a species entirely composed of females. They use the sperm of a closely related male species to trigger the replication of the entire maternal genome. They then birth live fish instead of laying eggs. It is expected that asexually reproducing species will develop a muller's ratchet of mutation over many generations but the Amazon Molly fish have not. Researchers have not found out why the Amazon Mollies have not developed a ratchet of mutations and believe the answer is in the genome of the fish.

ARTICLE Reproduction is through gynogenesis. This means although females must mate with a male, the sperm only triggers reproduction and is not incorporated into the already diploid egg cells the mother is carrying (except in extraordinary circumstances), resulting in clones of the mother being produced en masse. This characteristic has led to the Amazon molly becoming an all-female species. Other all- female species include the New Mexico Whiptail, desert grassland whiptail lizard,

In nature, the Amazon molly typically mates with a male from one of four different species, either P. latipinna, P. mexicana, P. latipunctata, or occasionally P. sphenops. One other male that could possibly exist in the Amazon molly's natural range that could induce parthenogenesis in Amazon molly females is the triploid Amazon molly males. These triploid males are very rare in nature and are not necessary in the reproduction of the species, which is why the species is considered to be all female.

The Amazon molly reaches sexual maturity one to six months after birth. An Amazon molly will not lay eggs but birth a brood typically between 60 and 100 live fry (young) being delivered every 30–40 days. This lends itself to a large potential for population growth as long as host males are present. The wide variability in maturity dates and brood sizes is a result of genetic heritage, varying temperatures, and food availability. They become sexually mature faster and produce larger broods in warm (approximately 27 °C) water that provides an overabundance of food.

The Amazon molly has been reproducing asexually for about 100,000-200,000 years, this is about 500,000 generations of Amazon molly. Asexual lineages typically go extinct after 10.0-100.0 generations. There is research being done to determine how the Amazon molly has not gone extinct or developed a Muller's ratchet of mutations. Researchers believe the answer is in the genome of the Amazon molly.