Biological Monitoring for MoCo

Field Reports from Department of Environmental Protection Staff

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Magical Fairy Shrimp

Posted by mocobio on June 30, 2009

Although most shrimp are found in oceans, fairy shrimp live in fresh or saltwater ponds. They are invertebrates, meaning they lack a backbone. Fairy shrimp are known as an indicator species because they are highly sensitive to changes in their environment. Since they are sensitive to environmental conditions, they are often used by biologists and ecologists to evaluate overall environmental health. If they are present and are found thriving, it can suggest a healthy environment supportive of their life-cycle needs for habitat, food, and reproduction.

Fairy shrimp live in small temporary water holes known as vernal pools, found in locations such as wooded areas, floodplains of streams and rivers, flooded meadows, coastal regions, wetlands, and swamps. These pools are also habitat to frogs, toads, salamanders, and crayfish. By definition, if a pool supports fairy shrimp, it is a vernal pool. Any changes in hydrology such as changes in groundwater, as well as quality and flow directions of surface water can negatively impact vernal pools. One of the biggest threats to vernal pools is the paving over of natural lands by pavement and concrete which prevents rainfall from percolating into the ground and changes the water balance in an area.

Look closely... like real fairies, they are hard to find! Fairy shrimp are obligate seasonal pool invertebrates... meaning they are only able to exist in these special seasonal pool habitats.

Look closely... like real fairies, they are hard to find! Fairy shrimp are invertebrates which only live in seasonal pools. Read our post 'Vernal Pools' to learn more.


Fairy shrimp spend their entire lives in these pools and have a fascinating life cycle.  The female drops her eggs to the bottom of the vernal pool, which in the mid-Atlantic region of Montgomery County MD, often dry by late summer.  The eggs go into a state of diapause in which they lie dormant through freezing and drying cycles.  The eggs can hatch years later, when conditions are favorable.  The sudden appearance of fairy shrimp, from seemingly nowhere, is how they acquired their name.

Close up of elusive fairy shrimp, whose eggs lie dormant for years.  When they hatch under favorable conditions, they seem to appear out of nowhere.

Close up of fairy shrimp, whose eggs can lie dormant for years. When they hatch under favorable conditions, they seem to appear out of nowhere, hence their name.

Fairy shrimp are fun to watch swim because of their eleven sets of appendages known as phyllopods.  Phyllopods are used in collecting food and locomotion.  Fairy shrimp swim on their backs fanning their phylopods. 

Watch a video of moving fairy shrimp that a County biologist caught on video were found west of Rockville near Seneca Creek State Park at McKee Beshers Wildlife Management Area.  Aren’t they magical?



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2 Responses to “Magical Fairy Shrimp”

  1. elaine holt said

    my daughter had a triop park for christmas and since then all that hashatched is this beautiful white fluffy looking creature not sure what it was until i looked at your website and it definatley a fairy shrimp they are so beautiful i am glad it was one of these instead of a triop i can watch it swim for hours

  2. Lulu Kury said

    Thanks for posting this subject. I had been looking for good information about it.

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