Moly vs Platy vs Swordtail

Hello fishy peoples. I have to confess that I find it difficult to readily distinguish between mollies, platies and swordtails, not to mention the many varieties thereof. I checked on Wiki and read that these fish all belong to the same family (Poeciliidae), but are classified in two different genera. These are:

Moly (Poecilia) = about 40 species. Guppies (and Endler’s Livebearer) are also contained in this genus.
Platy (Xiphophorus) = 2 species and many varieties.
Swordtail (Xiphophorus, i. e. same genus as platies) = 26 species. Some of these swordtail species are also called platties.

I have no idea how current or outdated Wiki’s information is, but that’s not really my concern right now. What I’m hoping from you is to identify my 2 attached pictures. These 2 specimens were found in an artificial dam in the Cape Town area. I’m guessing they are from the genus Xiphophorus, but I would prefer something better than a guess. So let’s hear it from the pros…

 

They both look like hybrids to me.

 

Both are definitely Xiphophorus, but as Nicolaas said, they could be Hybrids.
Swords and Platy's are known to cross breed.
They look more like swords to me though, One on the Left looks like a young male.

 

Thanks for your replies Nicolaas and Bees. So we can eliminate mollies (Poecilia) as a posibility. And I'm satisfied with an imprecise ID of Xiphophorus sp., or a hybrid within the genus. My "gut-feel" also tends towards swordtials.

 

There are three Xiphophorus that pop up regularly, or at least hybrids of them anyway: X. helleri, X. variatus, and X. maculatus. These are the ones that can be seen in a multitude of shapes, patterns and colours. Other species may be seen/imported but as far as I know tend to be kept 'clean' of other genes.

I tried running them through a key of the species of the genus, but came up with nothing definitive.

The longer shape says more sword, though.

Regards,

 

Damn fine answer - thanks for the details and for making the effort.

 

Btw SalmonAfrica, I don't know of many people that will actually bother to use taxonomic keys for ID purposes. Impressed ...

 

Thanks @Aquaphile - truth is that most pictures aren't clear enough to do scale or ray counts. These pictures have great detail which is fantastic.

 

Were they caught during this winter or a earlier month, they shouldn't be able to handle Wcape winters.

 

Yup most tropical fish won't be able to establish populations in WCape wetlands because of our cold winters, but it seems as though these "swordtails" can, or did so. They were captured 1 week ago (early June), and the park manager tells me he has seen them there for about 2 years already. So another exotic population has established, albeit in an atrificial wetland...

 

I remember reading somewhere that platies are rather capable of rather low temperatures for some extended period. I suspect its those genes kicking in there. I would however be interested in actual temperature values for the waters they're found in.

 

Ok Salmon, I will check water temps during my sporadic visits this winter and let you know