What is a Fairy Shrimp?

Last week’s weekly puzzler was an animal called a Fairy Shrimp. I know plenty of people who would say, “what the heck is a fairy shrimp?” I was once in that group too, but an experience working as assistant curator at a small nature center years ago in upstate NY opened my eyes to this fascinating creature.

Maybe I can open your eyes too to this interesting creature. Here are 8 facts about fairy shrimp:

1. Fairy shrimp inhabit vernal or ephemeral wetlands. These are temporary bodies of water that often dry up in the summer or fall and remain waterless until the following spring when rains and/or ice melt fills them up again.  This means that if you are walking through the woods in the fall, you might not even know you are passing a vernal pond, but if you returned in the spring, it might look completely different –and sound different too, considering all the animals who may be present. (Such as wood frogs, spring peepers, yellow spotted salamanders to name a few)

2. Fairy shrimp are relatives of lobsters and crabs. They are all crustaceans. Crustaceans are a kind of invertebrate, meaning they lack a backbone. Insects, spiders, snails, worms are other examples of invertebrates.

3. Fairy shrimp swim upside-down as they move through the water, filter feeding on algae and plankton.

4. Fairy shrimp have an amazing lifecycle, necessary since their pond may be dry for several months of the year. What I thought was most interesting is that females lay two different kinds of eggs–winter eggs and summer eggs. Winter eggs are called cysts and remain down in the mud at the bottom of the pond throughout the winter, until the pond has water again. This could be months, but it could also be years! Some fairy shrimp eggs in a lab hatched 15 years later! The winter eggs might be blown by the wind or carried away by an animal who has eaten them and will then poop them out in a different place. The eggs remain intact, despite traveling through the digestive tract of the other animal!

Summer eggs hatch out in about 16 days and then the fairy shrimp reaches sexual maturity at 41 days. The females will then lay 10-150 tiny eggs, with 22 being about the average. Depending on the temperature of the water, the eggs will hatch into mini fairy shrimp 16 days later.

5. Fairy shrimp are 1/2 to 1 inch long. They have large compound eyes, two pair of antenna, a long segmented tail, and 11-17 pairs of leaf-like appendages for swimming and respiration.

6. The color of fairy shrimp vary according to the food supply in the pond. It can be reddish, pink, even green or gray. All the fairy shrimp in that pond will be the same color, but those in another pond may be a different shade. (Fairy shrimp are filter feeders, eating algae and plankton.)

7. When the pond gets water in the spring, the eggs usually hatch out in around 30 hours. 

8. Fairy shrimp are eaten by lots of other animals! Including frogs and salamanders, birds and other invertebrates.