Emeraldking-aquatics livebearers


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.

Swordtails in the wild are divided into 2 groups: the southern and the northern swordtails. The northern swordtails are smaller in size and occur more in Belize, Honduras and Quatemala. The southern swordtails however do occur mainly in Mexico (for Xiphophorus signum and Xiphophorus mayae ain't endemic to Mexico) and are larger in size. The southern swordtails can be divided into 2 subgroups: the Helleri group and the Clemenciae group. To the Helleri group belongs X.helleri, X. mayae, X.signum and X. alvarezi. To the Clemenciae group belongs X.clemenciae, X.monticolus and X.mixei. Last 2 mentioned are very hard to find within the aquarium scene. In free nature depending on the location where the swordtails can be found, mutliple phenotypes will show up within each wild swordtail species. This has got to do with hierarchy and external factors like e.g., the available food sources, etc... And it seems that within the Helleri group multiple phenotypes are more at hand than within the Clemenciae group and the northern swordtail species. Some remarks can be made regarding the genetic history of the X.clemenciae and the X.monticolus. Both swordtail species seem to be evolved through a natural hybridization between swordtail and platy. Just the exact swordtail and platy ancestors are not clear identified. But both X.clemenciae and X.monticolus as current species are officially recognized as being swordtail species.

A quote from an article about the X.monticolus:
A good example of a wild swordtail species that has lost the sword trait secondarily is the Xiphophorus Birchmanni.
Above: Two male Xiphophorus Birchmanni (also known as sheepshead swordtail).
The sword of a male swordtail or male platyfish is an ancestral ornament. It's nothing more than a number of elongated lower finrays of the caudal itself. The sword is developed by upregulating (stimulation of the activity of certain receptors located on cells by hormones) the msx genes (methionine sulfoximine, this is an irreversible enzyme {glutamine synthetase inhibitor} which is responsible for morphogenesis of tissues).
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.
Above: Quoted from Manfred Schartl.

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).
For further info, I'd like to refer to the introduction chapter by clicking the button below:

Wild swordtails

Xiphophorus pygmaeus
One of the wildforms is the dwarf swordtail (xiphophorus pygmaeus). These dwarfs are to be found in the Pánuco River system in Northeastern Mexico.
It's a swordtail which really shows its wild nature in comparison to other swordtails. These are in some way shy fish which will hide when they can.
Above: An adult couple.
There are two versions: the golden and the blue version. The blue version is not blue but that's how the wild colour is called. But note that both females of the blue and gold version are blue. So, a golden coloured female doesn't exsist.
In captivity they grow  up to 4cm.
Xiphophorus continens
Another dwarf swordtail is the Xiphophorus continens and also known as El Quince swordfish.
This dwarf is to be found in Rio Panuco drainage in San Luis Potosi in mexico where it inhabits an enviroment with fast flowing water.
Just like the Xiphophorus pygmaeus, the males of this species carries also a very short sword. And some males just won't grow a sword which is also comparable with the Xiphophorus pygmaeus. The same goes for their size.
The stripe on both sides seems clearly different from their dwarf relative. 
It's a friendly swordtail which is suitable for smaller tanks but be sure of it that they still have sufficient swimming space for they are very vividly. 
Gestation will take up 3,5-4 weeks in general and the amount of fry won't be that large. A good batch will be at 10-15 fry each drop.
Above: An adult female.
Below: An adult male.
The males are quite slender in body build in comparison to females.

Xiphophorus multilineatus
Also a very interesting and beautiful dwaf swordtail is the Xiphophorus multilineatus. This dwarf is endemic to the Rio Choy of Rio Pánuco basin in San Luis Potosi in Mexico.
These swordtails will reach up from 4 cm to 5cm of length. That's just body length and the swordtail is not included yet. females tend to grow up a bit more in comparison to the males. If we look at the appearance of the females, they do have similarities to the females of the X.pygmaeus and X.continens.
Below: An adult couple.
Above: An adult female.
Best kept at moderate temperatures 22°C-25°C.
In some way there are very different visions on how hard they seem to reproduce. I myself haven't had any problems to get them to breed. To me it seemed that they reproduced easily. The offspring will look like the mother when it comes to their phenotype.
The gestation itself may take 3-4 weeks and an average batch of 5-15 fry will be born.
Above: A few weeks old fry.
Once the juvenile males will show their gender, the males will slowly change their colors and bodyshape. The horizontal stripe pattern will dissappear. And a lateral line which is edged shaped will remain on both sides. By the way, also the females will have such a lateral line. But depending on their mood and how the light will refelct their bodies, you'll be able to see more horizontal lines (which are not edged shaped).
The males will develop a yellow-orange coloration in the dorsal and caudal.
They prefer some water flow in the tank. So, be sure to give them that.

Xiphophorus helleri
The most known version of the swordtails is the regular green swordtail (Xiphophorus helleri). The subname "Helleri" is also spelled like "Hellerii". Both spellings are correct.  The subname "Helleri" is derived from the Austrian botanist and naturalist Karl Heller. Heller collected them and brought the first versions of this species to Vienna, Austria after a number of expeditions in Mexico during the period of 1845 - 1848. The species has been described for the first time by Johann Jakob Heckel (Austrian zoologist, ichthyologist and taxidermist) in 1848.
This is the most wide spread swordtail species and occurs in Mexico, Honduras, Guatemala and Belize. But also by translocation, the X.helleri is the most wide spread wild swordtail on this globe.
Because of the wide range of distribution of this species, the phenotypes may differ a lot from each single location. Not just coloration and pattern but also the size of the several X.helleri colonies differ. But in general a good adult size (without the sword) is between 7 - 12 cm. Of course, there are also larger and smaller ones (depending on a number of other factors).
Also the X.helleri is a good contender to keep outdoors during the better months of the year. This species does well between a range of 15 - 25°C.
The X.helleri is also the ancestor of many fancy swordtail strains within the aquarium scene by linebreeding and also by inbreeding with platyfish.
Overhere, a fancy swordtail strain (orange Mickey Mouse swordtail) of Xiphophorus helleri:
Xiphophorus nezahualcoyotl
The Xiphophorus nezahualcoyotl is also called Mountain swordtail or Northern mountain swordtail. Among keepers of this strain, they're also known as "Nezzies". The name "Nezahualcoyotl" means "hungry coyote". And this strain was named after an acolhuan philosopher, ruler and warrior by the name of Acolmiztli Nezahualcoyotl (☼1402 - †1472).
This sport inhabits fast till moderate flowing creeks in mountainous areas which are parts of the Rio Tamasi drainage (state of San Luis Potosi, Mexico).
This swordtail won't become that large and could be considered a dward swordtail as well. Average size of an adult male will be about 5 cm (sword not included). And an average size of a female will be 5-6 cm.
Xiphophorus Alvarezi
This swordtail is also called "Chiapas swordtail".
The X.alvarezi occurs in Rio Santo Domingo in the state of Chiapas in Mexico and Huehuetenango, El Quiche and Alta Veracruz in Quatemala.
This species is not the most easy swordtail there is. It might take a while before they'll reproduce themselves. In my opinion, is to leave those fish on their own for a while. Only observing and nothing more. In some way, they have to get adjusted to their enviroment all by themselves. Be sure that there's some water movement to make them more comfortable. 
Xiphophorus helleri yucatan
Another great wildstrain of swordtail is the Xiphophorus helleri yucatan. It's a swordtail which can grow up explicit larger than the average swordtail. 
This strain is from the Yucatán peninsula (Mexico). It concerns also a green swordtail (don't take "green" too literally) and as already been mentioned they do grow up large. There's one specific stripe on both sides of the body which shows very clear. This stripe is winered colored. But with dominant males you'll hardly see this stripe on each side. This is because dominant males tend to get a red or orange color which covers the whole lower part of the body which will cover the winered stripe. But sometimes a green male can become almost totally red instead of partially. But the number of males that will turn almost red is pretty low.
Above: An adult female. The winered stripe is explicit present.
Below: An adult male. This is clearly a dominant male. 
Below: A group of yucatan swordtails. In this picture are 2 red males to be seen. The upper one still shows some green under the red coloration on the upper part of the body. The lower red male is already totally covered with the red coloration and no green to be seen anymore. It's really remarkable that a green swordtail turns into a red swordtail.
These swordtails are highly profilic and even those fry already show a ferm body build. About eating their own fry is something I hear several stories about. But I honestly do have to mention that my experience with these fish is that fry won't be eaten. I just leave those fry in the open with those adults.
They do well at lower temperatures and for sure suitable to keep outdoors when the temperatures will allow it. I'd like to categorize this strain as being easy to keep.

Xiphophorus montezumae
The Xiphophorus montezumae ia also known as Montezuma swordtail.
The distribution of the habitats of this strain ranges from Rio Tamesi, Tamaulipas, Northern Veracruz and San Luis Potosi in Mexico.
Depending on the location, the specimens tend to look differently. Most wellknown version is the one with the typical black markings on their bodies. Both genders "can" have those spots but it seems that males tend to have more black markings in general in comparison to the females. Just a small number has some tiny black markings but most females don't have them.  But the amount of black markings also differ from where the original versions came from (so the locality where the originals were caught).
The picture
below shows a male which hardly shows black markings (just some tiny spots).
Something which is also very typical with montezuma swordtails is that you definitely know if you have a female or male when they're almost hitting adulthood. Late males do occur very often with this kind of swordtails as well. Also a clear gravid spot is not present with each female. 
It's a very vivid type of swordtail. Which means that they also need sufficient space to swim. Especially when males try to compete with another to see which might be the most dominant male, you need to give them the space they need.
Above: two adult males.
And it's not just because of their vividness that these swordtails need a large tank but it's also because of the sword which a male will develop. For this kind of swordtail will develop one of the largest swords of most known swordtails.
Xiphophorus helleri Rio Papaloapan
Another green wild form of swordtail is the Xiphophorus helleri Rio Papaloapan. This speckled type of green swordtail occurs in the Rio papaloapan stream in (state of Veracruz) Mexico.
This is one of the most way easiest wild strains there is. Thusfar is seems that they do well in a wide range of waterparameters. Even when it comes to reproduction they seem one of the most profilic ones. It also seems that they have a shorter gestation than other wild swordtails. My own experience shows an average gestation of 3 weeks. And the fry also grows up faster than most.  I do keep them at low temperatures and even with those rates they reproduce fast. 
Most fry show speckles already at an early stage. But the amount of body speckles do differ from fish to fish. 
This is an average sized swordtail which has a lack of dominant behaviour in a tank unlike a lot of other swordtail strains. Which makes this kind a good contender for a community tank.

Xiphophorus signum
The comma swordtail (Xiphophorus signum) is endemic to Rio Chajmaic in the state of Alta Verapaz in Guatemala. The first specimens of this strain were caught in 1963. This strain is a member of the southern swordtail clade and was described as a subspecies of X. hellerii (Rosen and Kallman, 1969; Morizot and Siciliano, 1982). Dr. Rosen (1969) elevated signum to a specific status with the most notable character being the presence of a grave spot, a micromelanophore pattern in the caudal of both genders.
Its name is derived from the the latin word "signum", which means mark or sign. It refers to the black comma sign on the lower part of the caudal. Both genders have the same comma sign. With fry this comma sign is not visible in the beginning but will show up while they're growing up. The same goes for the lateral line on the sides. This will show up while growing up. Unlike other wild swordtails, there's no diversity of pehenotypes. All specimens of this species are complete spitting images of eachother.
Once a male starts to develop his sword, the comma sign will elongate along with the sword and as the sword has reached its full length, the comma sign looks like a long black seam on the sword.
This comma swordtail is the only wild swordtail that has got higher first dorsal finrays in comparison to the rear dorsal finrays.
A unique feature of this swordtail species is that all attempts to crossbreed this species to another swordtail species failed thusfar. The conclusion is that this swordtail species won't interbreed with other swordtail (and assumable also not with platies) species. This makes the comma swordtail a good tankmate with another swordtail species without the risk of hybrids.
In 1979, Rosen studied both phylogenetic ( phylogenetics =  is a part of systematics that addresses the inference if the evolutionary history and relationships among or within groups of organisms (e.g., species) relationships and interbreeding potential of four breeding species of Xiphophorus. These species and their interrelationships are shown in the figure below (X. sp. is an undescribed species). Xiphophorus signum is the most derived species of the group and is reproductively isolated from X.hellerii, as shown by sperm competition experiments (a criterion well established for reproductive isolation among poeciliids). Xiphophorus signum is also reproductively isolated from X. alvarezi. But X. hellerii and X. alvarezi are completely infertile and hybridize and introgress where their ranges contact in nature. We may conclude that X. signum has different and apomorphic (distinguishing an organism or taxon from others that share the same ancestor) features incorporated into its reproduction and development, whereas X. hellerii and X. alvarezi are similar and plesiomorphic (sharing a chracter state with an ancestral clade) for these features (at least to the point that development is not impaired). Their ability to interbreed is due to the retention of plesiomorphic features, not to the fact that they are closest relatives. One should be aware of the assumption that the ability to interbreed denotes a close phylogenetic relationship, In this case, that criterion would have led to a mistake in analysis.
This brings up the interesting point that the significance of both hybridization and introgression depends on the phylogenetic position of the species.The ability to breed succesfully is, potentially, a primitive character. Within the history of any lineage, reproductive compatibility is an attribute of the members of the ancestral species of that lineage; an attribute which is gradually diminished and ultimately lost in its descendants during geographic differentiation. Reproductive compatibility is not necessarily evidence of close relationship.
Like some other swordtail species, the male characteristics will show up very late. Even females show a gravid spot for the first time pretty late. Therefore, only with almost full sized 7 cm (max. 10 cm without the length of a sword) specimens, it wil become clear what kind of gender they are.
Above: A male which starts developing a sword.
This southern swordtail resemble more the northern swordtail. Scientist believe that the comma swordtail is a primitive form of the swordtail fish in general which developed itself in an isolated area till a certain degree unlike other wild sworedtail species that have a wider range where they occur. And therefore they'll have more phenotypes than the comma swordtail.
These comma swordtail do fine at temperatures between 17 - 26°C. So, also this swordtail makes a good contender to keep outdoors during the better months of the year.

Xiphophorus kallmani
The Catemaco swordtail (Xiphophorus kallmani) also known as "Brass swordtail" occurs in lake Catemaco, Papaloapan drainage, Veracruz in Mexico. Don't mistake Catemaco swordtail with Catemaco platy (Xiphophorus milleri).
This swordtail does have a beautiful metallic golden shine on its body. There's not that much information about this species but it's been described by Manfred Schartl and Meyer (2003).
This species can reach up to 10 - 12 cm of length. They're quite hardy and do tolerate temperatures between 18 - 28°C.


Fancy swordtails

I'd like to reply on the frequent shown question at forums, which is: Are all fancy swordtails the result of a crossbreeding between swordtail and platy?  The answer is: No!  I do understand why people think that. For there are so many fancy platy strains that have the same coloration and/or pattern as many fancy swordtail strains. Most of them are a crossbreeding between platy and swordtail. But there are also fancy strains (specifically in the early years of fancy swordtails) that only have swordtail blood in them.
Just like other livebearer species it started with natural  mutations that were kept seperate and linebred with those specific traits that occurred by mutation. But also the color red that many fancy swordtails carry. Yes, there have been crossbreedings between platy and swordtail to pass on the red color. But in free nature red spcimens do occur. But be aware that such a red coloration has got a specific meaning with certain kinds of wild green swordtails. It marks down the pecking order within a group. For instance, this phenomenon occurs with a number of males of the Yucatan and Alvarezi swordtails. They're born as green specimens and will turn partially till total red as an adult. And it starts from the lower part of the body upwards. The degree of red coloration will impact the dominance of the male.
But if you linebreed the most red green males, the red becomes more present in the phenotype. At some point, you'll be able to develop just red swordtails as well. There are even females that will show red on their green body.
So, assuming that all fancy swordtails are "only" the result of a cross breeding between swordtail and platy would be an incorrect thought.
Xiphophorus helleri pearl white
Besides wildstrains, I also do keep and breed fancy strains. One of them is the white swordtail. Although white swordtail strains already exsist, it's a bit hard to get your hands on some where I'm located. So, I've decided to create my own whites.
I've used blue swordtails with koi (kohaku) swordtails back in 2015. It took a while before I had real whites. The male above and below does show some orange in its gonopodium (a left over from the koi swordtails). 
Above: One of the couples which shows already a lot more white (January 2016).
I've started culling those most white offspring to accomplish my goal.
Above: A picture of a male (January 2016) with still some blue and some orange. But most of those markings has dissappeared till the final whites occured.
Below: Two juvenile white swords.
Xiphophorus helleri red velvet
I do love red swordtails, despite of the fact that they're fancy swordtails. But the red velvet version is the one I love most. This red is darkred and yes, the skin looks like velvet.
These swordtails do grow up large and they've got a ferm body build. I do have to say that dominance among both males and females do occur very often with this kind.
They need a lot of space to develop a good bodysize. They're also very profilic and batches of 50-80 fry seems normal. and what's also remarkable is that they won't eat their fry. At least, by my own experience these adults will leave their offspring alone.
Above: an adult male with a good shaped body. It does show a healthy appearance. This one reached 13 cm (sword included). But several sizes will occur in each strain. But this is also a large male. But in the wild a number of wild species can even grow larger.
Below: Two pictures of clearly wellbuilt red velvet swordtails.
This hi-fin swordtail seems to be a chinese cross just like his cousin the "sabertail". The difference between the standard cauliflower and the sabertail is that the sabertail has got a saber shaped sword. The name "cauliflower" itself refers to the shape of the elongated dorsal of both genders. But the female has got a less elongated dorsal in comparison to the male.
It's got a sturdy build bodyshape, which is quite unique for a swordtail fish. In my opinion the bodyshape reminds me of a mix of swordtail and molly.
They're red eyed which would make them suitable for a tank with dimmed light. Most albinos and lutinos are sensitive to bright light.
Among fancy swordtails, this sports is a majestic one. Its whole appearance shows class, strength and respect.
Above: An adult male.
Below: An adult female.
Above: Even from the top they look majestic.
For more fancy swordtail strains, I'd like to refer to the legend chapter by clicking the button below: