L. Lee Cerny
Fairy Shrimp (Class: Branchiopoda
Order: Anostraca)
ADULTS
REPRODUCTION
Fairy shrimp are beautiful animals (up to 1.5 inches long) that may appear “like magic” in vernal pools.
To reproduce, the male will grab the female with his claspers and the two swim around for several days. Hours after copulation, which can take a few minutes, the male dies.
Fairy shrimp are among the most developed invertebrates. They have eleven pairs of legs, a pair of stalked eyes, and a strong tendency to move toward light. They swim upside down and can remain in the same position, move gracefully, or dart about in the water. Males have long claspers on their heads, while females have a brood pouch in which the cysts are carried.
Male (top) and female (bottom)
L. Lee Cerny
They are a mid-level predator feeding on algae, protozoa, rotifers, and detritus. They are preyed upon by waterfowl and diving water beetles.
74
Fairy shrimp can appear under the ice in some areas and usually die out when the water reaches 60 degrees F. Depending upon the conditions, fairy shrimp can live out their life cycle in as little as 16 days.
The female has a brood sac that can contain anywhere from 10 to 150 cysts. Cysts are fully developed embryos enclosed in a hard, spongy shell. After several days, the cysts will be released and fall to the pool floor. Given certain conditions, only 3% of all cysts will hatch. This evolutionary survival mechanism ensures that not all cysts are hatched and die in unfavorable conditions. The cysts can survive ingestion by animals and can be blown by wind to other areas. Another survival mechanism is the two types of eggs laid by fairy shrimp. There is a “summer” cyst, which has a softer shell, and a “winter” cyst, with a harder shell. In laboratory settings, cysts have been viable after being exposed to temperatures as high as 210 degrees F and as low as -526 degrees F.