Emeraldking-aquatics livebearers

Xiphophorus

This genus exists of swordtails and platies (also called platyfish). The name "Xiphophorus " is a composition of two greek words, meaning "dagger" and "bearer". Looking at swordtails, you'd expect it to be referred to the swordshaped tail but it actually refers to the gonopodium.
Note: Not all swordtail males do develop a sword and with some platy strains males can develop a very short swordtail. With this being said, the sword (elongated lower finrays of the caudal) seems to be a sexual preferable trait to female swordtails and female platyfish. It's known that swordtails and platyfish are able to interbreed with another. It's also known that female livebearers decide wether a certain male is allowed to mate with her (no matter how often a random male may chase her and even tries to aim his gonopodium in her direction). But if a male swordtail or a male platy with a sword is present, she'll most likely prefer such a male to be her mating partner instead of a male with no sword. Which makes it also more likely that a female platy will choose to mate with a swordtail than with another platy when both species are kept together in one tank. So, in reference to mating selction in general, female of Xiphophorus species prefer swords of male swordtails and platyfish more than the coloration on the male's body.

Swordtails inhabit waters ranging from Belize, Honduras, Guatemala and mainly Mexico. Platies however occur only in Mexico. Swordtails do occur in freshwater but also in brackish waters. They can even get used to marine water just like mollies. But just like guppies, swordtails and platyfish were also introduced by man to other waters all over the world. For a lot of swordtail strains do occur in higher situated areas where it can be a lot colder which makes them excellent inhabitants in other colder areas. This tells us as well that we should label swordtails as being subtropical instead of tropical.
There are so many different swordtail and platy strains in the wild. The fancy swordtail strains we know are all derived from the Xiphophorus helleri and the fancy platy strains from the Xiphophorus maculatus and the Xiphophorus variatus. But again, besides these three... there are way more wild strains of swordtails and platies.
All swordtail and platyfish species found in other areas on this globe are introduced by man and are therefore feral strains.

Overhere a summary of all wild caught swordtails and wild caught platyfish (which were used for research) and their GPS locations as far as known of course:
Overhere a phylogenetic tree of all known wild Xiphophorus species:
Note: Males of the xiphophorus species may develop a socalled "pseudo gravid spot". This phenomenon happens mostly with platy species in comparison to swordtail species. Mostly such a pseudo gravid spot will be developed during or after the transition of the anal fin into a gonopodium. It hardly happens before the anal fin's transition.This has got nothing to do with a female turning into a male. For that's a different story.
A gravid spot of a female is the most translucent part of the skin while a pseudo gravid spot is developed in the skin (and absolutely not translucent). But once a pseudo gravid spot is developed, it will never fade nor disappear.
Above: An adult male Xiphophorus evelynae.
Note: Once a pseudo gravid spot has shown on a male's body, it will never dissappear.

Sex change:
Xiphophorus species "can" be born with both male and female gonads. Generally spoken, an initial male will absorb the female gonads and an initial female will absorb the male gonads while growing up. But in some way this absorption doesn't always seem to happen the way it suppose to be. Which makes it possible that female specimens can change gender. Even when she's been pregnant before. But in that case, the female will keep her gravid spot. And the transformed specimens will be functional males when it comes to reproduction. But yes, also old females can change gender after they've had their defininite last batch of fry. In general, such a transition will take place after a certain trigger (only possible as long as such a female is an Aa genotype). An example could be an unbalanced male/female ratio within the group or even a lack of hiearchy within the group. But there are more triggers to establish a sex change.
Males however can not change gender for the transition of the anal fin into a gonopodium is irreversible. In the past I've put pregnant females seperate. They've dropped fry and some changed into functional males. I've put some together with young virgin (but already sexually mature) and they were impregnated by transformed females. The offspring were fertile.
Of course this is written in a way that it's understandable for an average person who's just interested in how this works. To give away a bit more of information, I do have to mention that with Xiphophorus species we're not dealing with just 2 sex chromosomes (X and Y) like most animals have but with 3 sex chromosomes: W, X and Y.
 
Note: A sex change does not only happy to Xiphophorus species. It can also happen to a number of other kinds of livebearer species. But not with all kinds. But it happens mostly with Xiphophorus species as best known livebearer family.

If there's a lack of males or even no males within a group but there are fry present, you'll notice that there will be fast developing young males. These males stay small in comparison to an average male's body size. This is to ensure the reproduction and the exsistance of the species. What's also remarkable with early males is that the majority of their offspring will be male at an average temperature. With late males a majority of female offspring will be the result (and again at an average temperature).

Wild platies

Xiphophorus variatus La laguna
This wildstrain can be found close to the east coast of Mexico (state of Tamaulipas). The habitats has got a wide range from southern Tamaulipas, eastern San Luis Potosi and northern Veracruz. In general they inhabit  slow flowing till still waters.
This species does well at lower temperatures and after an average gestation a female will drop between 5-20 fry in general. Good thing is that also this strain will leave their newborn fry at ease. So, creating a colony without a threat of fry eating is potential. 
Despite of the fact that males tend to become very colorful, it will take quite long before a male will have its final colors. But not all males will be that bright colored. For it's mostly the dominant males which will become the best colored specimens within the colony. Females don't have that much color but they're well-speckled for that matter. And some females do tend to have somewhat yellow in their fins.
Above: A juvenile male which is starting coloring up.
The ones in my possesion are descendants from the wildcaughts by McAllister.


Xiphophorus evelynae
A wildstrain platy close related to the Xiphophorus variatus is the Xiphophorus evelynae. This strain is also known as Highland platy.
This platy is mainly found in the Rio Tecolutla stream.
This species prefers densely vegetated tanks to hide and sufficient swimming space for they tend to be vividly. Despite of their vividness, they're real friendly fish. 
In general they're greyish till lightbrown bodied with some spots on their body. They do show some yellow in their fins.
Above: An adult male.
Below: Two adult females.
It's a profilic kind of fish which doesn't seem to chase their fry. Also with this strain I do keep the new offspring with the adult fish. 
While doing well at lower temperatures makes this a very easy to keep type of fish. A real good contender to keep outdoors during spring and summer.  


Xiphophorus xiphidium
This species mentioned is also called "One spot platy".
This platy is endemic to Rio Santa Engracias at Tamaulipas in Mexico. It's a platy which has got a short bottomsword unlike other platies. It's a vey easy and hardy fish to keep. The name "One spot"seems very obvious in this case.
When males age they tend to get a hump on their backs and tend to develop a pseudo gravid spot. Further on they can also develop a couple of vertical bars on both sides of their body. Males size up to 4cm and females up to 5 - 6cm.
Below: A juvenile couple of Xiphophorus xiphidium.
The one spot strain which I'm keeping came from a generation wild caught fish in 1978. And there was no influence of other platy strains involved.
Above: An adult female and a juvenile male (the anal fin is already changing into a gonopodium)
There are also two other variations of the Xiphophorus xiphidiumcalled "Two spot platy" and "Crescent platy". The two spot platy is to be found in Rio Purification and the crecent platy in branches of Rio Soto La Marina.
Below: A small group of Xiphophorus xiphidium crescent.
 
 
Xiphophorus milleri
This platy is also called "Catemaco platy".
This species is endemic to the Papaloapan ecoregion (state of Veracruz)  in Mexico. This platy occurs in shallow tributaries of Lake Catemaco and in shallow mouths (brackish water) of inlets along the shoreline.
It's a yellow bronze bodied paty with speckles and mostly a crescent mark at the rear. There's a real difference in body build in comparison to the xiphophorus maculatus. 
There are also darker bodies males which seem to be also smaller than their bronze coloured relatives. Those darker bodied ones came to adulthood too fast (determined on the Y-chromosone). While regular males size up to approx. 4cm, these dark males will size up to approx. 2,5cm. Females however can size up to 5cm.
After a gestation of 3,5 - 4 weeks a number of fry will be born between 10 - 40. The adults will hardly chase their offspring. 


Xiphophorus maculatus, Chuco's place
A wild Xiphophorus maculatus platy species found in a small lake at Natural Park Biosphere Reserve Pantanos de Centla in Mexico is the following maculatus species as shown below.
The ones I got came from Kees de Jong (friend, author, co-editor at Poecilia Netherlands and a huge wild livebearer enthusiast like me). He caught them back in 2019 when he went on an expedition. He caught them from a small lake called "Chuco's place"(coordinates: 18.37166 - 92.69411), named after a commerical cichlid collector named Chuco. Remarkable is that this small lake is almost completely covered with water lettuce (Pistia stratiotes) and crocodiles are present overthere. In this lake occur as well Pseudoxiphophorus maculatus, Gambusia sp. and Dormitator maculatus.
 Above: An adult female.
Below: An adult male.
This X.maculatus version is grey bodied. Both genders have a round black spot on both sides of the shoulder. On the caudal penducle is a dark pattern to be seen (which is called a Mickey Mouse pattern or marking). This specific marking is also to be seen in several fancy strains of the Xiphophorus maculatus (the commercial name for such platies is Mickey Mouse platy and comes in several body colors). Btw, there are several kinds of wild platy strains that have a marking (shape may differ) on the caudal penducle.
Despite of the fact that these are wildcaughts, they seem pretty hardy. No problems whatsoever keeping them in captivity.

Fancy platies