Invertebrates

Fairy Shrimp

Anostraca · also called fairy shrimp

Not Evaluated filter feederomnivore Rivers & wetlands Desert Polar & tundra

A fairy shrimp lives its whole life on a deadline. When winter rain or snowmelt fills a shallow pool, the shrimp hatch from eggs that have been lying in dry dirt for years, drifting upside down through the water and filtering algae with rippling legs. Within a couple of weeks they mate, lay a new batch of drought-proof eggs, and die as the pool evaporates around them.

Overview

Fairy shrimp are the crustacean order Anostraca, about 300 species, found on every continent including Antarctica. They have no shell, a soft body often tinged pink or green, and 11 or more pairs of leaf-like legs that they beat while swimming upside down, using the same motion to swim, breathe, and filter-feed. They live only in temporary pools — vernal pools, desert playas, snowmelt ponds — because those waters contain no fish, and a fairy shrimp has no defence against fish at all.

Surviving the dry

Adults die when the pool goes. The eggs — thick-walled cysts — sink into the mud and can survive years or decades of drying, freezing, and heat, hatching only when the pool refills. Typically only a fraction hatch at each filling, holding the rest back in case the pool dries too soon.

Why the pools matter

A newly filled pool’s bloom of fairy shrimp is a critical food pulse for migrating waterbirds — the reason places like Mono Lake host vast flocks of phalaropes and gulls. Brine shrimp, the “sea monkeys” of salt lakes, are simply the salt-adapted members of this same group.

Status

Not evaluated as a group; widespread species stay common. But temporary pools are among the most destroyed habitats on Earth, and many narrow-range fairy shrimp are threatened — four California vernal pool species are federally listed.

Fairy Shrimp: common questions

What is the difference between a fairy shrimp and a brine shrimp?

A brine shrimp is a fairy shrimp. Brine shrimp, genus Artemia, are the members of the fairy shrimp order Anostraca that specialise in very salty water such as salt lakes and coastal salt pans. Other fairy shrimp live in fresh or only slightly salty temporary pools. They share the same body plan, swimming upside down with no carapace and beating many leaf-like legs to filter food, and the same trick of drought-proof eggs. The everyday distinction people make is by habitat, using fairy shrimp for the freshwater vernal-pool species and brine shrimp for the salt-lake ones sold as sea monkeys and as fish food.

How do fairy shrimp survive when their pool dries up?

The adults do not survive; they die when the water goes. What survives is the eggs. Females produce thick-walled resting eggs, called cysts, that sink into the mud and enter a dormant state in which they can withstand total drying, high heat, hard freezing, and long periods with no oxygen. They can stay viable in dry soil for years and, in some species, for decades. When the pool refills with cool, oxygenated, low-salt water, a portion of the eggs hatch within a day or two, and the rest stay dormant as insurance in case the pool dries again too soon.

Are fairy shrimp the same as triops?

No, though they often share the same pools and both are branchiopod crustaceans with drought-proof eggs. Fairy shrimp are slender, soft-bodied, and shell-less, and they swim upside down in open water filtering tiny food. Triops, or tadpole shrimp, are much larger and sturdier, with a broad shield over the front of the body, and they crawl on the bottom scavenging and hunting, including hunting fairy shrimp. In a freshly filled desert pool you may find both, with clouds of fairy shrimp in the water column and triops working the mud below.

Can you hatch fairy shrimp at home like sea monkeys?

Yes. Kits based on native fairy shrimp, and the familiar brine shrimp sea monkey kits, both work the same way, in that you add the dried eggs to suitable water and they hatch within a day or two. Freshwater fairy shrimp generally need cool, clean, dechlorinated, low-mineral water and steady cool temperatures, closer to conditions in a snowmelt pool, and they are a little more demanding than brine shrimp. They are often reared as live food for fish and amphibians and are used in classrooms to show a complete short life cycle.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Anostraca
Diet: A filter feeder that swims on its back beating 11 or more pairs of leaf-like legs to create a current, straining algae, bacteria, protozoa, rotifers, and fine detritus from the water and passing them forward along a groove to the mouth, with a few larger species also actively seizing prey
An upside-down life: A fairy shrimp spends almost its whole life swimming slowly upside down, back toward the bottom, the rippling motion of its many legs serving at once for swimming, breathing, and feeding, and it has no shell or carapace at all, leaving the body soft and often tinged pink, green, or blue
Temporary pools only: Fairy shrimp live only in waters that regularly dry out, such as vernal pools, desert rain pools, snowmelt ponds, and rock basins, because these hold no fish, and a fairy shrimp is defenceless and would be eaten out within days anywhere fish can reach
Eggs that outlast the drought: Females release tough-shelled resting eggs, or cysts, that settle into the dried mud and can survive years or decades of complete drying, freezing, and heat, hatching only when the pool refills under the right conditions, and usually only a fraction hatch at any one filling as a hedge against a false start
A life measured in weeks: Once a pool fills, fairy shrimp hatch within a day or two, grow through a series of moults, and can be mature and laying eggs in one to three weeks, racing to finish the life cycle before the water disappears, and the adults die when the pool dries
From deserts to Antarctica: Fairy shrimp are found on every continent, including Antarctica, where one species lives in meltwater pools, and they include the brine shrimp of salt lakes and the large predatory Branchinecta of the American West, with about 300 species worldwide, many known from only one or a few pools
A feast for waterbirds: When a vernal pool or playa fills, the sudden bloom of fairy shrimp is a vital burst of food for migrating and breeding waterbirds, and the shrimp and their eggs are a major reason such wetlands matter for shorebirds, ducks, and, at places like Mono Lake, huge numbers of phalaropes and gulls
Range: Every continent, in fresh and saline waters that dry out seasonally, including vernal pools, prairie potholes, desert playas and rain pools, alpine and Arctic snowmelt ponds, rock pools, roadside ditches, and salt lakes, from below sea level in desert basins to high mountain tarns, with individual species often restricted to one climate zone or even one cluster of pools.
Conservation status: Not Evaluated ≈ The group as a whole has not been assessed, and widespread fairy shrimp remain common wherever temporary pools survive. But temporary pools are among the most heavily destroyed of all habitats, ploughed, drained, filled, built over, or altered by roads and by deliberate stocking with fish, and many fairy shrimp species have tiny ranges confined to a single pool complex or region. Several are formally protected, including four vernal pool fairy shrimp in California listed as Endangered or Threatened under United States law, and species in South Africa, the Mediterranean, and Australia are considered at risk. Because the eggs persist in the soil, a lost pool can sometimes be restored, but a pool that is graded flat or paved is gone for good in the wild