X. continens RAUCHENBERGER,
KALLMAN, & MORIZOT 1990
The El Quince swordtail is known from
only a single short headwater spring of the
Río Ojo Frío, where it is sympatric with X.
montezumae. In stark contrast to its cousin,
X. continens males only possess a tiny
sword, reach about an inch in body length,
and prefer the heavily planted areas of the
biotope. The lack of exaggerated finnage,
pigment patterns, courtship rituals, and
large size makes it an anomaly among
platies and swordtails, and the species is
being studied extensively.
The late Derek Lambert found this
species a peaceful and easy charge in the
home aquarium. Temperatures in the low
70s are recommended.
X. multilineatus requires heavily planted tanks with plenty of hiding places.
Reaching sizes of 1½ inches at most, X. nigrensis is a colorful swordtail for a smaller aquarium.
The Montezumae Clade
The northernmost swordtails are
separated from their cousins by the
folded ridges and valleys north of the Río
Tampaón–Río Santa María Axis (San Luis
Potosí and Tamaulipas). The clade contains
three species that seem to have little
relation based on outward appearances, but
proximity and genetics indicate otherwise.
KALLMAN, & MORIZOT 1990
Nezzies are the northernmost swordtails
and are widespread at varying elevations
(and temperatures). Fortunately, the
populations floating around the hobby
in the United States—“El Salto” and
“Ocampo”—are from the Xiphophorus
Genetic Stock Center and prove hardy.
Nezzies are playful fish famous for their
long, curved swords. They seem to be found
mostly in waters with good current with
rocky bottoms. X. nezahualcoyotl is named
after the emperor of the Texcoco nation,
similar to the naming of X. montezumae
for the Aztecs. From the 1960s through
the 1980s this fish was thought to be the
Montezuma swordtail, and older books will
display it as such.
JORDAN & SNYDER 1899
A great show fish whose sword length is
the stuff of legend, this species (along with
Endler’s livebearer guppy) helped create
a livebearer renaissance at the turn of the
millennium that we enjoy today.
In the hobby there is a Rio Gallinas complex
of mottled fish: “Rascon,” “Tamasopo Wessel
’98s,” “mottled ivories,” “El Quince,” and
an Arroyo La Ciénega complex of green-yellow solid fish: “ojo caliente,” “capuchin,”
and “blue-green.” I distributed three of the
populations extensively several years ago
and fear that hybrids within the various
populations may be happening now in the
hobby. Keep your fish pure with collection data!
It only takes a couple of emails to track down
your fish’s history.
Montezumae swords are often found in
clear, open waters near springs, rivers, and
waterfalls. All the males have the characteristic
sworded tail that can be up to three times
their body length ( 10 inches total fish length),
as well as a large, rounded dorsal.
Males can take one to two years to sex
out, confusing hobbyists into thinking they
have a tank full of female fish. Temperatures
in the mid-70s suit them well.
The species suffers from a convoluted
history, only being rediscovered by the hobby
in the 1990s, nearly 100 years after its initial
discovery by legendary ichthyologist Seth Meek.
During the 20th century, several imposters in
the form of hybrids and other species were
given the designation “montezumae” until
Rauchenberger, Kallman, and Morizot sorted
things out in 1990 thanks to their diligent field
collection data via the Xiphophorus Genetic
Stock Center. I penned a two-part investigative
report on the Montezuma swordtail in my April
and May 2005 TFH columns (“Montezuma’s
Revenge” and “Montezuma’s Revenge, Part 2:
Strains of the Day”).
That concludes our five-part series on the
exciting Xiphophorus livebearers. I hope you
will try to enjoy this diverse and exciting
group of fishes in your own aquarium.
Cummings, M. E., G. Rosenthal, M. Ryan.
2003. “A private ultraviolet channel in visual
communication.” Proceedings in Biological Science
Fisher, H. S., and G. G. Rosenthal. 2007. “Male
swordtails court with an audience in mind.”
Biological Letters 3: 5–7.
Rauchenberger, M., K. D. Kallman, and D. C.
Morizot. 1990. “Monophyly and geography of the
Río Pánuco Basin swordtails (genus Xiphophorus)
with description of four new species.” American
Museum of Natural History 2975: 1–41. D
Tropical Fish Hobbyist www.tfhmagazine.com