Devils Hole pupfish

Cyprinodon diabolis

FAMILY

Cyprinodontidae

TAXONOMY

Cyprinodon diabolis Wales, 1930, Devils Hole, Ash Meadows, Nevada, United States.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

A dwarf species seldom exceeding 1 in (2.6 cm) in length. Pelvic fins are absent. Resembles the juvenile pupfish. Sexually dimorphic and dichromatic. Males have iridescent blue body color; the operculum is iridescent with a purple sheen. The unpaired fins are bordered in black, the dorsal fin is iridescent gold, and the anal and caudal fins are whitish toward the base. Prominent genital papilla. Females overall have more yellowish coloration than males. The back and caudal and pectoral fins are yellowish brown, and the dorsal fin is edged in black. The operculum is metallic green, with a hint of a dark bar on the caudal peduncle.

DISTRIBUTION

Ash Meadows, Nevada.

HABITAT

The enclosed pool of an aquifer formed by flooded limestone caverns and reached by a 49 ft (15 m) naturally occurring shaft in the side of a hill, its only source of light. The dimensions of the entire pool are 11.5 ft by 72 ft (3.5 m by 22 m). A boulder divides the surface of the pool into two sections. The breeding and most of the feeding, upon which the survival of the species depends, take place on an algae-covered rocky shelf 11.5 ft by 16.6 ft (3.5 m by 5 m) with 1 ft (0.3 m) of water above it. The shelf is situated at the foot of the shaft. The overall dimensions of this part of the pool are 11.5 ft by 42 ft (3.5 m by 13 m). At the end of the shelf there is an abrupt drop-off of 28 ft (8.5 m). The substrate continues to slope downward below that depth. Water flows in and out of the pool at a year-round temperature of 90°F (32°C). As the lakes and waters of the area disappeared and the desert formed, the species was trapped in the aquifer 10,000 to 25,000 years ago.

BEHAVIOR

The pupfish exhibits a daily cycle of movement to and from the rocky shelf, depending on the time of day and the time of year.

FEEDING ECOLOGY AND DIET

In the summer and fall the species feeds chiefly on the algae growing on the shelf. Algae also grow on the substrate just off the shelf up to a depth of 50 ft (15 m), with only trace amounts below that. In winter and spring, when the algae are much reduced, diatoms are the chief food items. The population varies from about 200 to 500 individuals, depending on the algae growth.

REPRODUCTIVE BIOLOGY

Males do not set up breeding territories, as do other pupfish. Spawning takes place primarily in April and May. Males closely accompany a ripe female to the algae-covered shelf, where they stay together and spawn at irregular time intervals spanning about one hour. The species has spawned in the laboratory, but no eggs were hatched.

CONSERVATION STATUS

Listed as Vulnerable by the IUCN.

SIGNIFICANCE TO HUMANS

The pupfish has endured in its tiny habitat for as many as 25,000 years, providing us with a stimulus to ponder both the durability and the vicarious nature of life.