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.
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