Endler’s guppy or Endler’s livebearer?

Seeing this small colorful fish, most people, including many representatives of pet companies and even fish breeders, will say it’s Endler’s guppy. But is this the correct name for this species? Endler’s guppy or Endler’s livebearer? Which name is correct?

To explain this, I will start with the systematics of these fish. The guppy (Poecilia reticulata) and the Endler’s livebearer (Poecilia wingei) belong to the same genus Poecilia in the family Poeciliidae. However, they have been classified as two separate species.

Endler’s livebearer was indeed originally known as Endler’s guppy. It was first caught in 1937 by Franklyn F. Bond. But it wasn’t until its rediscovery in 1975 by John Endler and a certain coincidence that aquarists have heard of it. You can read more about it in my text about Endler’s livebearer (Poecilia wingei) – wild phenotypes. Since 2005, the fish has been known as Poecilia wingei. Thus, we are dealing with two distinct genres, which, when we look closely, are clearly different.

So, taking into account the current systematics, it can be concluded that the name Endler’s guppy is an outdated and incorrect name. Unfortunately, it is difficult to explain it to people on the Internet. Just like it’s hard to debunk other aquarium myths that are alive online. People easily and without much consideration share false information (such as that the betta fish does not need filtration). Another issue is that a genuine Endler’s livebearer that would not be crossed with a guppy is hard to get, especially in Poland.

What is the difference between a livebearer and a guppy?

Let’s turn to the differences between Poecilia reticulata guppy (based on farmed forms of these fish) and the Endler’s livebearer Poecilia wingei (based on wild forms of this species). Male Endler’s livebearers are filigree, small in size. They grow to only about 2.5 cm in length. Their caudal fin is short and round, never fully colored. It can be partially patterned or have the outline of a lower sword, upper sword or double sword. The guppy is definitely larger. Depending on the group and standard, it has a more impressive tail fin. The most impressive tail fins can of course be observed in fish from the long-finned group. In addition, the tail fins are all colorful. The P.wingei ‘s tail base is much thinner compared to P.reticulata. Their dorsal fin is also more impressive compared to the Endler’s livebearer.

As for the females, significant differences can be seen at a first glance. Female Endler’s livebearers grow to about 4 – 4.5 cm. Female guppies are much larger, more stocky and clunky. It can be said that female Endler’s livebearers are definitely more slender and guppy females – more square. As for coloration, female livebearers are gray or olive-gray. Their caudal fin (especially in wild forms) is always colorless, without any patterns. Female guppies may have colored fins. The number of offspring is also much smaller compared to the guppy. This is related, among other things, to the size of mature females. Importantly, P.wingei females do not eat their own fry. The two species can crossbreed, which is very common.

Hybrids of Endler’s livebearers and guppies

Unlike Poecilia reticulata, which are divided into groups and standards, Poecilia wingei fish are divided into classes. In Endler’s livebearers, three classes are distinguished: N, P and K. Fish with a documented wild origin are marked with Class N. Class P is marked for fish that have phenotypic characteristics resembling or looking like wild fish but have no documented origin, while Endler’s livebearers crossed with guppies are designated class K.

However, it should be noted that in order for hybrid of an Endler’s livebearer and a guppy to be classified as class K, it is necessary to select and stabilize the line. In other words, breeding should be carried out in such a way that the features of the external structure of the fish show that it has a predominance of the characteristics of a livebearer rather than a guppy. Here I am mainly referring to size, body structure and fin shape.

How I created my Endler’s livebearers line

I created the line of fish shown in the photo, using Saddle back mosaic male guppies , which I crossbred with females of the wild variety of Endler’s livebearers. I then crossed males from the first generation with the mother, and in subsequent generations with sisters. With each successive generation, for further breeding I selected the males that I liked the most and which showed the features I was most interested in (small size, round tail, outlined swordtails). The final result I got was as shown in the photo above. Of course, the first-generation fish left much to be desired (photo below by Bartek Gorzkowski). It also depends a great deal on whether you mate a male livebearer with a female guppy or vice versa, as in both cases you will get fish with different characteristics.

Class K, therefore, should not be called the first generation of fish after the mating of a livebearer and a guppy. The discussions on this issue with other aquarists led us to the conclusion that such fish are safest to designate as Poecilia sp. In my opinion, only fish from established lines with distinct characteristics of Endler’s livebearer should be included in the K class.

Buy fish wisely

If you are interested in breeding Endler’s livebearer or guppies or you just like a particular line of these fish and want to buy quality fish, always thing before you act. Be sure to verify the information provided by vendors. If someone presents one aquarium and talks about selection and work on a particular lineage, and there are females of other species of the genus Poecilia swimming in the tank, he or she is simply trying to deceive you. We have many excellent breeders in our country who have achievements in breeding work with guppy and win awards in Polish, European or world championships. You should get information and knowledge about these fantastic fish from these people.

Endler’s livebearer in the end

In conclusion, the correct name for the species in question is Endler’s livebearer. Therefore, we should use this very name and promote it, despite the immense popularity of the incorrect name “Endler’s guppy.”

I wish everyone breeding success.

Wojciech Golianek