A desert that waits for water
The Tengger Desert, whose name means “Sky” in Mongolian, covers approximately 36,000 square kilometers in north-central China. It is a dynamic landscape of shifting, crescent-shaped dunes, and it is China's fastest-moving desert. The region receives little rainfall, with an annual average of only 115 millimeters. However, this arid environment holds a secret within its dry basins: the potential for life to erupt suddenly.
Hundreds of saltwater and freshwater lakes are scattered throughout the larger Alashan desert region, which includes the Tengger. Many of these are ephemeral, meaning they are temporary. Following infrequent, heavy summer rains brought by the East Asian Monsoon, these basins can quickly fill with water. This dramatic change transforms the landscape and awakens a dormant ecosystem. The water's appearance is the critical trigger for a unique biological event centered around a tiny, resilient crustacean. This phenomenon is a remnant of a much wetter past, as geologic evidence shows that a massive "Megalake Tengger" covered over 16,000 square kilometers of this region during the Pleistocene epoch.
The rapid life of a brine shrimp
The explanation for this instant ecosystem is the brine shrimp, a small crustacean of the genus Artemia. Female brine shrimp have a remarkable reproductive strategy. When environmental conditions are stable, they give birth to live, swimming young, a method called ovoviviparity. When conditions become harsh—such as when a lake begins to evaporate—females switch to producing dormant embryos encased in a hard shell. These shelled embryos, called cysts, enter a state of suspended animation known as quiescence, where their metabolism nearly stops.
The cysts, measuring just 0.2 to 0.3 millimeters in diameter, accumulate in the dry lakebed sediment. They are incredibly durable, capable of surviving complete desiccation, extreme temperatures and oxygen deprivation for many years. The reason for this survival is a sugar called trehalose, which protects the embryo's cells from damage during dehydration. When rain finally fills the lake, the cysts rehydrate, and the embryos resume development. Triggered by light, they hatch into free-swimming larvae, called nauplii, within 24 to 36 hours.
These nauplii grow with astonishing speed, molting up to 15 times. They reach adulthood, about one centimeter in length, in as little as eight days to two weeks, feeding on microscopic algae that also blooms in the temporary lake. The adults mate, and the females produce a new generation of cysts before the lake evaporates again, completing their entire life cycle in a matter of weeks and leaving a "gene bank" in the mud to await the next rains.