Cyprinodon alvarezi (MILLER, 1976) -Potosí Pupfish

Etymology

The name “Cyprinodon” is derived from the Ancient Greek words “κυπρῖνος” (kuprinos), which means “carp,” and “ὀδούς” (odous), which means “tooth.”

The species name “lvarezi” is a tribute to José Alvarez del Villar, a friend of the author who discovered and collected this species in 1952. Initially, Alvarez del Villar intended to describe the species himself, but later entrusted the task to the author.

Classification

• Order: Cyprinodontiformes
• Family: Cyprinodontidae

Distribution

This species was originally found exclusively in a solitary spring located near the town of El Potosí in the northern Mexican state of Nuevo León. However, it has been extinct in the wild since the late 1990s.

Habitat

The original location where this species was discovered was a single pond that received its water from a natural spring. This pond was situated in an endorheic basin called “La Hediondilla” at the base of “Cerro Potosí” mountain, with an elevation of approximately 1880 m above sea level.

The pond had undergone modifications, including the construction of an earth and rock dam, which enlarged its size. Below the pond, there were several distributaries extending for 1-1.5 km. The water in the pond was crystal clear and had abundant vegetation, including species of Ceratophyllum, Najas, Nasturtium, and Utricularia.

In addition to this species, the pond was also home to another endemic pupfish species called Megupsilon aporus, and an endemic crayfish species known as Cambarellus alvarezi. Unfortunately, the pond has since completely dried up due to water exploitation for irrigation and other human uses.

Goldfish (Carassius auratus) were introduced into the pond before 1961, and largemouth bass (Micropterus salmoides) were first observed in 1974. Correspondingly, there was a decline in the population of cyprinodontid species.

Between 1983 and 1984, the water level of the pond dropped by 1.5 meters, and by 1985, the pond had disappeared, leaving only a trickle of water in the distributaries. Although slight recovery was observed during the early 1990s, only negligible populations of the endemic species were supported, and by 1996, the water had completely disappeared.

Maximum Standard Length

• 50 – 60 mm.

Aquarium Size

While a 60 x 30 cm aquarium or equivalent may suffice for a single pair, this species, like other members of the Cyprinodontidae family, thrives better in a larger tank or container as a group.

Maintenance

The aquarium setup for this species does not have to be overly complicated, as long as there are ample broken lines-of-sight. It is recommended to provide plenty of cover in the form of aquatic plants, wool mops, and other structures. If filtration is necessary, air-powered, sponge-type units are the best option as they do not harm eggs or fry.

While lighting is not necessary, it can be utilized if desired. The growth of filamentous algae should be encouraged if possible.

Water Conditions

• Temperature: 17 – 26 °C
• pH: 7.0 – 8.0
• Hardness: 179 – 357 ppm

Behaviour and Compatibility

It is best to maintain this species alone, particularly if the goal is to encourage breeding. However, with adequate space and careful research, they can also be kept in a community setup.

Individual males require enough space to establish territories, but in most cases, multiple males can coexist in the same aquarium.

Notes

Due to its current existence solely in captivity, the preservation of this species is crucial. Therefore, it is not recommended for community fish keeping.

References

1. Contreras-Balderas, S. and M. de L. Lozano-Vilano, 1996 – Ichthyological Exploration of Freshwaters 7(1): 33-40
   Extinction of most Sandia and Potosí valleys (Nuevo León, Mexico) endemic pupfishes, crayfishes and snails.
2. Miller, R. R., 1976 – Bulletin of the Southern California Academy of Sciences v. 75 (no. 2): 68-75
   Four new pupfishes of the genus Cyprinodon from Mexico, with a key to the C. eximius complex.
3. Miller, R. R. and V. Walters, 1972 – Contributions in Science (Los Angeles) No. 233: 1-13
   A new genus of cyprinodontid fish from Nuevo Leon, Mexico.