Jeweled Splitfin

Jeweled Splitfin Xenotoca variata (Bean, 1887)

Also known as: Pintada, Jeweled Variata

Max Size: 6 cm (males) / 7 cm (females)

A shimmering highland gem from central Mexico. Males of the jeweled splitfin are living jewelry boxes — grayish-green above and white to yellow below, with dark fins edged in yellow on the caudal, and covered in large, multi-colored iridescent scales that flash green, gold, and silvery “jewels” along their flanks. These reflective speckles are more than decoration: research shows denser iridescence signals stronger fighting ability and better access to females. Females are more understated — grayish-brown with a dusky head and irregular dark blotches that often form a mid-lateral stripe. Both sexes have the classic goodeid “splitfin” (notched anal fin) in males, used for internal fertilization.

Origin & Habitat Endemic to the central Mexican highlands across the states of Aguascalientes, Guanajuato, Jalisco, Michoacán, Querétaro, San Luis Potosí, and Zacatecas. It inhabits the Lerma–Grande de Santiago basin, Río Grande de Morelia system, and parts of the upper Pánuco drainage. Typical habitat includes clear to murky springs, shallow rivers, lakes, and ponds with submerged vegetation, algae-covered rocks, and substrates ranging from mud to gravel, usually in slight current or still water at depths under 2 m and temperatures of 20–30 °C.

Diet Omnivorous with a carnivorous lean. In the wild it consumes crustaceans, insect larvae, worms, algae, and aufwuchs. In the aquarium it readily accepts high-quality flakes, granules, freeze-dried or frozen foods, and vegetable matter.

Behavior & Temperament Generally peaceful but males can be mildly territorial, especially when competing for females. Best kept in groups with more females than males. They occupy the bottom to middle levels of the aquarium and appreciate both planted cover and open swimming space.

Reproduction Viviparous livebearer typical of the Goodeidae. Males use the modified, notched anal fin (andropodium) for internal fertilization. Females give birth to well-developed young after a gestation of roughly two months. Broods are produced regularly under good conditions; juveniles are relatively large at birth.

Conservation Status IUCN: Least Concern (2018 assessment).

Although still relatively widespread and more tolerant of habitat alteration and pollution than many other goodeids, populations have declined in parts of its range due to water pollution, habitat modification, and invasive predators such as largemouth bass. Several Evolutionary Significant Units (ESUs) are recognized, some of which are more vulnerable than the species as a whole. A distinct form from the Lake Cuitzeo / Río Grande de Morelia basin may represent an undescribed species.

An attractive, hardy, and scientifically interesting goodeid whose males flash living jewels to win both fights and mates — a perfect showcase species for planted aquariums and a reminder of the rich (and still-threatened) diversity of Mexico’s highland fishes.