Animalia Life
Xenotoca eiseni
FAMILY
Goodeidae
TAXONOMY
Xenotoca eiseni Rutter, 1896, near Tepic, Nayarit, Mexico.
OTHER COMMON NAMES
Spanish: Mexcalpique cola roja.
PHYSICAL CHARACTERISTICS
Males grow to 2.4 in (6 cm) in length and females to 2.8–3 in
(7–8 cm). Sexually dimorphic and dichromatic. All fins are
rounded. The dorsal fin of males is larger than that of females
and is set over the anal fin, far back on the portion of the body
that tapers to the caudal peduncle. The body is block-shaped,
with a humpbacked appearance in mature fish. The depth of
the caudle peduncle is much smaller than the body depth. The
head is small and pointed. The basic background color of the
body is brownish gray to beige; the degree of dark pigmentation
is quite variable. Males are bright orange to red at the
base of the caudal peduncle, with iridescent blue highlights on
the forward part of peduncle between the anal and dorsal fins.
The middle portion of the body has gold highlights, and the
abdomen is reddish to yellowish near the operculum. The dorsal
fin is sometimes black, the caudal fin is orange to yellow,
and the anal fin is orange. Color patterns and intensities vary
greatly by location, with colors in alpha males very pronounced.
Females have a grayish beige body color, sometimes
with silvery highlights; all fins are slightly yellow.
DISTRIBUTION
Mexico in Rio San Leonel, El Sacristan, and Rio Grande de
Santiago drainages in Nayarit; also in Rio Tamazula, Jalisco.
HABITAT
Found in rivers, streams, and springs as well as in ditches,
which are sometimes highly polluted.
BEHAVIOR
Collects in groups that have an alpha male. Males constantly
pursue females and are pugnacious and scrappy toward each
other and especially toward other species. In aquaria they have
the reputation of being fin nippers.
FEEDING ECOLOGY AND DIET
Omnivorous.
REPRODUCTIVE BIOLOGY
A live-bearing species with internal fertilization, the embryos
being nourished by trophotaeniae. The gestation period is
about 60 days. Brood size ranges from 10 to 40 fry, with reports
of up to 100 fry.
CONSERVATION STATUS
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
The redtail splitfin is sold in the aquarium trade and is bred
and traded by live-bearer aquarium hobbyists.
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