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What kind of fish is that? It's a common question for a keeper
of the Endler's Livebearer. Metallic reds, greens, yellows, and
oranges patterned with jet-black streaks or spots make this fish one of
the most colorful of all the freshwater species. The color itself would
be enough to attract anyone with an interest in keeping freshwater
fish, but look a bit deeper and you'll discover a history just as
colorful. We'll touch on that rich history here just a bit, then
we'll turn our attention toward keeping this fish. Lost and Found The Endler's livebearer (hereafter referred
to as endlers) were initially discovered by Franklyn F. Bond in 1937 in
the Cumana region of northeastern Venezuela. Specimens ended up in the
University of Michigan's Museum of Zoology, but the discovery was
never published and the fish never distributed. It took until 1975 for the fish to be
rediscovered, this time by Dr. John Endler. He provided samples to Donn
Eric Rosen, a noted Poeciliid taxonomist. Had Rosen been able to
classify the fish before he passed away, much of the controversy might
have been avoided. A Common Name Rosen did provide some of these fish to another
friend of Professor Endler, Klaus Kallman, who was then of the New York
Aquarium. Kallman introduced this fish to the German aquarium community
under the name Endler's livebearer. He apparently intended the name as a surprise for
Professor Endler. As it turns out, nobody told Endler, and he did not
encounter the fish as his namesake until sometime in the early
1980s. Official Classification As the endler made its way through the aquarium
community in Europe and eventually North America, a behind-the-scenes
battle raged between those who considered the endler a separate species
and those who considered it simply a unique strain of guppy. Detailing
this controversy would require a separate article, but suffice it to
say that the disagreements got quite heated. Finally, in 2005, Dutch ichthyologist Fred Poeser
and colleagues Michael Kempkes and Isaäc
Isbrücker published a paper classifying the endler
taxonomically for the first time as a unique species. They named the fish Poecilia wingei, to
honor Dr Ãjvind Winge, a Dutch geneticist who performed
significant early genetic work with guppies. The classification was not
without controversy. Two years later, Tropical Fish Hobbyist magazine
ran an article by frequent contributor Ted Coletti adamantly refuting
the classification. While there remains considerable controversy
among experts, the aquarium community at large seems to have embraced
the classification P. wingei. But Are They Really Endlers? One factor that complicated classification was
the ability of the endler to breed with the guppy. Cross-breeding is so
rampant that almost all enders found in retail are hybridized with
guppies.
In fact, hybridization is such a problem in
endlers that John Endler, along with several important breeders,
collectors, and avid hobbyists took the unusual step of creating a
special classification system. This system is used on auction sites and
in local clubs, and is presented here so the reader will be able to
interpret the classifications if encountered. Class N: Pure endlers directly descended from and
fully traceable to fish collected in the Cumana region of
Venezuela. Class P: Any endler thought to be pure but lacking
the requisite traceability for the class N category. Class K: Any endler hybridized with any other
livebearer species (most often guppies). True or False? None of this should be take to mean that there is
anything wrong with endler hybrids. As long as the hybridization is
done responsibly and the fish are not represented as pure endlers,
hybrids can make attractive additions to a community
aquarium. Unfortunately, this is often not the case. These
fish are commonly passed along to the general public under the name
endler or Endler's livebearer. Close inspection by a knowledgeable
eye reveals these fish to be hybrids. To the casual aquarist who takes
a label at face value, a disservice has been done. Compounding the
problem is that in many cases, the retailer is completely ignorant of
the misrepresentation. The main problem is that most endler hybrids
available in big box or local fish stores look an awful lot like true
endlers. In some cases the differences are so subtle that a trained eye
is needed to distinguish a hybrid from a true endler. How Can You Tell? Some endler hybrids look so much like a true
endler that it's nearly impossible to distinguish them. The
world's most prominent breeder of the endler and of specialty
strains of endler-guppy hybrids goes by the trade name AdrianHD. He has
identified a number of clues to distinguish between a true endler and a
hybrid.
The coloration of endler males makes the job of
distinguishing them from hybrids far easier than with the plain
females. Black in endlers is very dark, and all other colors are
metallic. One theory behind the metallic coloration is that
these fish lived in algae-filled green water, and the metallic flecks
allowed females to see males. For the aquarist, it helps with
identification of hybrids. If a fish displays any pastel color, it is
hybrid. Other clues are more subtle. The caudal peduncle
(tail muscle area) of the true endler is narrow and elegant. The same
area on many hybrids resemble that of the guppy, which is thick and
meaty. Hybrid fish often display swords on the top,
bottom, or both sides of the caudal fin. While true endlers can display
very short swords, these mostly consist of coloration within the caudal
fin against transparent areas. These swords do not extend more than a
millimeter or two past the end of the caudal fin. A sword that extends
much beyond that is a sure sign of a hybrid fish. The aquarist must be cautious if white appears on
a male. Some strains of true endlers do occasionally display white, but
white will never occur in some strains, such as the black bar.
Knowledge of the strain in question is required to use white as a clue
to detect a hybrid.
What About Females? Distinguishing a true endler female from a hybrid
is considerably more difficult than with males. A true endler female
has a rich golden color. A guppy female is more silver in color.
Distinguishing pure female endlers from guppies is easy. Unfortunately,
a hybrid might be either color, or somewhere in between. That means
that other clues are needed. As with the male, the caudal peduncle of the
female true endler will be narrow. Along with the silver coloration, a
thick peduncle is the best direct indicator of a hybrid female endler.
Individuals from any given hybrid litter can have
considerable variation. In some cases, a hybrid fish can look so much
like a pure endler that the only way to distinguish it as a hybrid is
through characteristics of male siblings. Handling Hybrids Responsibly The pervasiveness of hybrid endlers in the
industry is so extreme that unless the shopkeeper can trace the fish to
a known keeper of class-N fish, any endlers for sale must be assumed
hybrid, or at best considered class P. That isn't necessarily a problem. For the
casual aquarist, hybrid endlers make great pets. However, keep in mind
that under proper conditions any livebearer will reproduce at a
surprising rate. Sometimes these offspring are given or sold to other
aquarists. It is critically important to represent these fish as the
hybrids they are, and not as pure endlers unless they meet the strict
class N requirements. This responsibility must be taken seriously to
prevent unintentional further dilution of the P. wingei species. The
fact that hybrids are advertised as endlers in the aquarium trade
greatly increases the odds that hybrids will unintentionally be further
crossbred with pure animals. The Good Side of Hybrids Hybrid endlers aren't necessarily all bad.
While endlers will cross-breed with fancy guppies, these hybridized
fish can display an amazing variety of interesting colors and
patterns. The world's most important breeder of the
Endler's livebearer, AdrianHD, has responsibly developed several
very special hybrid strains. By keeping the hybrid fish well-separated
from his class-N populations, AdrianHD has line bred such strains as
the tiger endler and the snakeskin endler. These are gorgeous fish that
combine the most attractive aspects of the endler and fancy
guppies. Most carefully-developed hybrid endler strains
are harder to find than a simple visit to the local fish store.
Usually, they must be acquired through other hobbyists, fish clubs, or
online auctions. They can also, of course, be purchased directly from
AdrianHD through his Swamp River Aquatics
business. What About Purists? Hybrids are one thing, but the avid aquarist most
likely wants to have 'the real thing.' The question is where to
find class N endlers. While occasionally somebody might bring a litter
of pure endlers into the local fish store (as this author has), it
doesn't happen very often. More likely, a local aquarist might
bring a small collection of juveniles to a club auction. If class-N endlers can't be found locally,
the only other practical solution is mail-order. When done properly,
shipping fish works surprisingly well for not only endlers, but for
most freshwater species. Auction sites like Aquabid often list endlers,
but the bidder must perform due diligence. Ask the seller about the
lineage of the fish in question. The best way to ensure the fish purchased are truly class-N endlers is to go directly to a known breeder or keeper of them. AdrianHD often sells pure endlers directly and through Aquabid. He also keeps a website called Endlers-usa.com. On this website you can find a list of known keepers and breeders of class-N endlers with contact information and sorted by strain. It is also a good place to network with other endler enthusiasts.
One row of the enormous fishroom where AdrianHD
breeds and maintains class N Endler's Livebearers, specialty endler
hybrids, and other livebearers. Photo by AdrianHD Swamp River
Aquatics. Class-N Strains Developing hybrid endler strains is not
AdrianHD's main focus. He is dedicated to the preservation and
distribution of the species. He has thousands of gallons dedicated to
class-N endlers, maintaining genetically diverse wild stock as well as
line breeding special strains. He breeds a number of other livebearers
as well. Probably the most well-known strain of ender is
the black bar. The males display a jet-black comma over the ribs,
making a sharp contrast with the metallic coloration. Another
well-known strain is the peacock. This strain has the jet-black color
on the body, but not as consistent in shape as the black bar. However,
there is always a black spot on the caudal fin that resembles the spots
on the tail-feathers of a peacock bird. Other strains developed by
AdrianHD include lime green and fire red flame tail. Fishkeeping Conditions Like most commonly available livebearers, endlers
enjoy warm water. They are very comfortable at 82°F (28C),
and may be able to tolerate brief periods of time in water as warm as
94°F (34C). The endler is an excellent choice a for hard
water aquarium. They prefer hard water and planted tanks. Fry will hide
in floating plants, but will also hide in dense areas of plants on the
substrate. Endlers of all ages will graze algae from the surface of
leaves. It is difficult to think of a more peaceful fish
than the endler. They make great tank mates for other peaceful fish
provided sizes are compatible. Of course, the conscientious aquarist will ensure
diversity to avoid genetic defects caused by excessive
inbreeding. Behavior Endlers display some of the most entertaining
mating behavior of any freshwater fish. Males will strategically
position themselves in front of a female, extend their fins to make the
largest display their colors, then perform a shimmying
dance. As a rule, the females are not impressed. In
response to this display, she seems to roll her eyes and swim away. The
male, however, is not easily discouraged. He will reposition himself in
front of the female and repeat the display. Eventually, the female has enough and darts away.
At this point, the male often realizes his display isn't working
and resorts to hit-and-run mating. The female can usually maneuver
through plants and eventually lose the male, who then looks for another
female and starts again. As a token to the persistence of the male endler,
they breed like, well, guppies. Like their more familiar cousins,
endler females will drop a litter of fry, then store sperm and continue
to drop fry for upward of six months. Responsibility The very fact that females can store sperm makes
it imperative to follow good fishkeeping practices. Never keep endlers
and guppies in the same tank. Breeding of class-N endlers should be
done with virgin females to ensure the offspring continue to be
class-N. Even if indifferent about the purity of endlers in
their own tank, the fish keeper should never pass hybrid fish to others
as pure endlers. The native habitat of the endler (and all other
livebearers in the Cumana region) is in danger due to human activity
and invasive cichlid species. That makes it especially critical that
the aquarium community keep these fish responsibly, because one day it
may be the only place to find them.
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