Jeweled Splitfin, Xenotoca variata
Jeweled Splitfin, Xenotoca variata, Female. Fish caught in a small lake within the Mexican Plateau in west-central Mexico, Michoacán, February 2017. Length: 4.4 cm (1.7 inches). Catch, photograph, and identification courtesy of Ryan Crutchfield, Tampa, Florida.
The Jeweled Splitfin, Xenotoca variata, is a member of the Splitfin or Goodeidae Family, that is known in Mexico as pintada. Globally, there are five species in the genus Xenotoca, all from the freshwater systems of central mainland Mexico.
The Jeweled Splitfin has an elongated and narrow body with a pointed snout and an elongated caudal peduncle. They are sexually dimorphic with males being grayish-green dorsally and white to yellow ventrally; they have dark fins, a yellow margin on their caudal fin, and large greenish to yellowish reflecting scales on their sides. Females are grayish-brown and slightly darker dorsally with a dusky head and dark spotting of various sizes that form a mid-lateral stripe.
The Jeweled Splitfin is a demersal species that is found at depths up to 2 m (5 feet) in clear warm springs with submerged vegetation and algae covered rocks, in open murky water, or close to shore near reeds over gravel, muddy, and sandy bottoms with slight current flows and consistent year-round temperatures between 20oC (70oF) and 30oC (85oF). Their maximum length has not been reported. They are omnivores and feed on algae, detritus, fish fry, water insects, and other small invertebrates. Reproduction is viviparous and involves internal fertilization followed by a short gestation period. Each female gives birth to young that can survive on their own but are subject to cannibalism on a limited basis.
The Jeweled Splitfin is found in Mexico’s freshwater systems and has a larger distribution than most Splitfins. They are found in the Río Pánuco and Río Santa Maria on the Atlantic slope and in the Ríos Lerma-Grande de Santiago basin and the Río Grande de Morelia basin on the Pacific slope in the states Aguascalientes, Guanajuato, Jalisco, Michoacán, Querétaro, and San Luis Potosí.
The male Jeweled Splitfin is straightforward to identify, however, the female Jeweled Splitfin is very similar to the Butterfly Splitfin, Ameca splendens (black caudal stripe) and the Polka-dot Splitfin, Chapalichthys pardalis.
They have not been assessed from a conservation perspective, but should be considered Near Threatened as they have disappeared from several known sites and are now found only in a few small and isolated new locations. The water habitat in some parts of their range has experienced a staggering amount of degradation during the 20th century and they are heavily preyed upon by various birds and recently introduced non-native fish including Black Bass, Guppies, Largemouth Bass, Sunfish, and Tilapia. They are utilized by the aquarium trade on a limited basis but they require large tanks, frequent water changes, and strictly controlled temperatures with an abundance of plant life.