Midvalley fairy shrimp facts for kids

The midvalley fairy shrimp (Branchinecta mesovallensis) is a tiny freshwater crustacean. It is usually about 7 to 20 millimeters long. This shrimp lives only in certain shallow pools in California's Central Valley.

These pools are called ephemeral pools. This means they fill with water during the wet season and then dry up completely. These special places are also known as vernal pool ecosystems. Many unique plants and animals live here. They are all adapted to the changing water levels.

What is a Midvalley Fairy Shrimp?

The midvalley fairy shrimp is one of eight types of branchiopods found only in Northern California. Branchiopods are a group of crustaceans. The word "Branchiopoda" means "gill feet." This is because these animals use their legs to breathe.

This shrimp swims on its back. It uses two eyes on stalks to see. It moves by beating its special legs, called phyllopods. These legs look like small leaves or paddles. As the phyllopods move, they also act like gills. They pull oxygen from the water, helping the shrimp breathe.

Fairy shrimp are part of the order Anostraca. This means they do not have a hard shell covering their head and back. This hard shell is called a carapace.

How Midvalley Fairy Shrimp Eat and Live

The midvalley fairy shrimp uses its phyllopods to filter food from the water. It eats tiny things like phytoplankton (tiny water plants). It also eats bacteria colonies, rotifers, protozoa, and small larvae. The food is then moved to its mouth through a groove on its belly.

Besides helping with movement and breathing, the phyllopods also help the shrimp manage salt in its body. This is important for living in different water conditions.

Scientists officially named the midvalley fairy shrimp in 2000. It looks a lot like other fairy shrimp species. Male midvalley fairy shrimp have special antennae. These antennae are used to hold onto females during mating. Females have a pear-shaped brood pouch. This pouch holds their eggs.

Life Cycle and Survival

Midvalley fairy shrimp can grow up very quickly. This is especially true in warm, shallow pools. They can become adults in about 8 days. But on average, it takes about 26 days. If there's enough rain, new groups of shrimp can hatch multiple times in one wet season.

These shrimp survive when their pools dry up by laying special eggs. These eggs have very tough shells. Inside, the tiny shrimp embryos go into a sleeping state called diapause. These sleeping eggs are called cysts.

Not all cysts hatch at once when the pool fills again. This means they create a "seed bank" in the soil. This bank can produce new shrimp populations even years later. Some cysts from related species have hatched after many decades!

Cysts are also very tiny, about 0.27 millimeters. They can pass through the digestive systems of birds or mammals without harm. This means animals can carry the cysts to new places. This helps new groups of shrimp start in different pools.

Where Midvalley Fairy Shrimp Live

Midvalley fairy shrimp have been found in many places in California. They live in shallow vernal pools and vernal swales. They also live in human-made wet areas like roadside puddles and ditches.

Vernal pools are shallow dips in the ground. They have soil that doesn't let water drain away easily. So, they collect water when it rains. Then they dry completely in the dry season. Special plants grow here that are used to these conditions. Vernal swales are similar but are more like channels that carry water between pools.

The shrimp seem to do best in shallow, cool water. They prefer water that doesn't have too much salt. However, they can handle warm water. They have even been found swimming in water as warm as 32°C (90°F). They can also live in some pools that are a bit salty.

A study in 1998 looked at the pools where eight types of branchiopods lived. It found that midvalley fairy shrimp lived in the shallowest pools. On average, the pools were only about 10.1 centimeters (4 inches) deep.

Conservation Concerns

The midvalley fairy shrimp lives in several California counties. These include Sacramento, Solano, Yolo, Contra Costa, San Joaquin, Madera, Merced, and Fresno. Since 2003, more places where these shrimp live have been found. As of 2006, there were 63 known locations.

Because the species was only officially described in 2000, scientists are still learning about its full range. Many sightings might have been missed before 1998. This is because the midvalley fairy shrimp looks very similar to other fairy shrimp species.

Like many vernal pool species, the midvalley fairy shrimp faces threats. Its habitat is under pressure from new buildings and farms. Changes to water flow also harm their homes. These problems have been happening for a long time in California.

There are many people moving into the areas where the shrimp live. Also, new projects, like the University of California, Merced campus, could affect their habitat. Losing their homes is a big concern for these tiny creatures.

The information in this article comes from a public document called "Recovery Plan for Vernal Pool Ecosystems of California and Southern Oregon."