A "Mystery Molly from the Amazon?" (Well, no...But wait, there's more!)

Everyone likes a good story. Everyone has one of those fishes that, for whatever reason, capture their imagination, right?


Well, I was doing just fine until one day, in conversation, my friend Luis Navarro were talking about biofilms and the occasional algae tufts that you find on wood, pods and leaves in a botanical-influenced aquarium, and he just HAD to mention in passing something to the effect of, "Oh, by the way, Mollies love that stuff...you should find Poceilia formosa. It's called the Amazon Molly...lives in blackwater."


Apparently, yeah.

It's not from the Amazon, despite its common name. Range is listed as "Gulf Coast from Rio Tuxpan, Mexico, north to southern Texas; possibly native to coastal portion of Nueces River and around Kingsville, Texas; certainly native to lower Rio Grande (where common); introduced in San Marcos and San Antonio rivers, Texas (Lee et al. 1980, Page and Burr 1991)."

I got suckered by the "Amazon" part right away.

I wonder how it acquired the name "Amazon Molly?" That answer was rather easily found with a bit more research; more on it in a second.

Okay, not from the Amazon. I get it. However, it IS found in blackwater environments! A quick search on the venerable fishbase.org site yields this tantalizing information: 

"(Found) In backwaters and quiet pools of streams, sloughs, and ditches, usually over mud. This is an all-female species thought to have originated as a result of hybridization between P. latipinna and P. sphenops. Gynogenesis reproduction is triggered by copulation and stimulation by sperm from males of other species in the genus, either P. latipinna, P. mexicana, P. latipunctata, or rarely P. sphenops."
So, not only do we have a Molly found in BLACKWATER environments, but it's a species that has a most unusual reproductive mode as well. The Amazon Molly reproduces through a process called gynogenesis, or "sperm-dependent parthenogenesis." This means that, although females need to mate with a male, the genetic material from the male is not incorporated into the egg cells the mother is carrying (except in extraordinary circumstances), resulting in clones of the mother being produced.
This unusual characteristic has made the Amazon Molly an all-female species. A lot of cool advantages, including the fact that they have twice the amount of "grandchildren" as Mollies that reproduce sexually! 
Crazy cool. 
And helpful from a commercial standpoint. I mean, if a vendor tries to sell you a "male Amazon Molly", he or she is- well- full of it. A built-in "b.s. detector" comes "baked right in" to the species! Nice, right?
Oh, and let's be honest about another thing. This species...is not gonna win any awards for it's looks. It's about as dull golden-brown as a fish can be. And believe me, I'm a lover of my brown and grey fishes, but this is one you keep because you love the whole fish- the name, the range it's found in, the whole gynogenesis thing...ANYTHING but it's looks.
(Photo by Dr. Michi Tobler)
Of course, there's that name.
Why "Amazon?" Did Jeff Bezos buy the rights to the species? Was the original ichthyologist who described the fish get confused about where he collected it from? You know, a miscalculation of a few thousand miles. No biggie?
Nope. Further hunting (I LOVE the internet!) reveals the true story behind the name. According to Wikipedia:
"The common name acknowledges this trait (gynogenisis) as a reference to the Amazon Warriors, a female-run society in Greek mythology."  
Ahh. Mystery solved. Very cool. And appropriate. But kind of a bummer that the fish is not found in the Amazon, and that the name is not a reference to its wild range, right?
Well, the cool thing is that it does come from environments that most of us wouldn't think would be "Molly-friendly"- blackwater pools and such. This makes this fish a sort of interesting subject for us, doesn't it? Couple it with the fact that it likes to graze on biofilms and algae that occur in these environments, then it's a pretty useful species, too.
And let's be honest, the golden brown/grey color isn't that bad, is it? Looks good against more colorful fishes, and the deep browns of our botanical-influenced aquariums.
Ok, maybe I'm reaching. It is sort of...dull.
Nonetheless, I have much respect for this species, despite being tricked by it's tantalizing name...I think I still want to obtain some specimens (female, of course!) for my blackwater tanks! What a conversation piece it makes, if nothing else!
So, the moral of this story? Look beyond the initial thing that attracted you to a fish...there might just be more to it; every bit as interesting, too.
Stay engaged. Stay relentless in your pursuit of the truth.
And Stay Wet.
Scott Fellman
Tannin Aquatics



Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

July 23, 2021

Hi Blake!

Still haven’t found it! We’ll keep looking, though!


david maddox
david maddox

July 22, 2021

Hey did you ever find these? I’m obsessed with having some but can’t find for sale. Guess I’ll have to go find them myself!

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