A fairy shrimp tale

Head of male fairy shrimp, color it pink and orange, or blue and glreen

April is the month for pranks and foolishness, and an inedible (by us) freshwater shrimp with no shell certainly seems to fill the bill. Yet every April a small pink  crustacean appears at very select pools across Maine and the country. This is Eubranchipus ssp, more commonly known as fairy shrimp.

Spring is a frenzy of reproduction for many species, and vernal pools are the nurseries for some of them, including salamanders, frogs, mosquitoes, and fairy shrimp. I wish I knew who came up with the name fairy shrimp. The males have bizarre fleshy claspers and look like the model for some of the creatures in a Star Wars’ bar scene, and the female’s eggs are visible in a large sac as they rotate like laundry in a front loading washing machine. Fairy shrimp are cool, but I grew up on Disney films and just cannot see the connection to Tinkerbelle or Merryweather.

It seems their sudden and brief appearance in spring, and equally quick exit, has a magical quality, and so the name fairy. Since their existence is dependent on many things, including us, this name may work in their favor. “Fairy shrimp” is enchanting, and who cannot want to know more and be supportive?

Much magnified (and fuzzy) head with charming protruding eyes.

I first learned about fairy shrimp as a student in the Maine Master Naturalist program. We needed to know that any vernal pool that had fairy shrimp was therefore a significant vernal pool (SVP), as specified by the Army Corps of Engineer. Then a friend told me they had looked for fairy shrimp for years. My freshwater life field guide by Elsie Klots says “their discovery always seems to mark an occasion for the collector.” All this made them seem rare, so I never expected to find them, and really did not have any driving need to do so. Instead, I wanted to learn more about caddisfly larvae. So I dipped my net in a small man-made firepond, with styrofoam and debris floating about, hoping for a few particle-encrusted specimens, and instead scooped up a dozen or more pale salmon-pink fairy shrimp. There was no doubt, nothing else looks like them. Yes, my eyes probably widened and a squeal may have come out of my mouth.

Yes, they do swim on their backs

Fairy shrimp are in the order anastraca, which means without a shield, or shell. They swim on their backs, gill feet gracefully moving back and forth. They are the favorite food of amphibians, and the caddis fly larvae I had gone looking for. They are in that pond maybe a month. Last year after my first scoop I became a bit obsessed, and went every few days. Ten days after my discovery there was not one, no matter how many times I scooped.

The fairy shrimp near my house are a soft rainbow of pink, salmon and orange. Their color is determined by what they have been eating. In other locations, they might be white, green or blue. They eat algae, bacteria, and other microscopic organisms by pulling them in with their feathery legs. Those legs also help them get oxygen from the water, as well as propel them about the pond at dizzying speed.

Females, the ones with the washing machine egg sacs, can reproduce with fertilization or by parthenogenesis (no male needed). There are far more females than males. Eggs (which are actually not eggs but cysts since they contain a fully developed embryo) are released over several days, sometimes 250 in a day. These drop to the bottom of the pool. In early spring if there is a shortage of males, females may lay an early batch of eggs that quickly develop, and also reproduce. Later in the season thicker-walled eggs are deposited and overwinter. These thicker-walled eggs can survive the winter, and even many decades, until conditions are right for them to emerge. Then they continue the cycle by swimming in starts and stops, reproducing, and dying. Even when conditions are right, not all cysts will hatch. Many will remain dormant for years. This a good contingency plan, because should an event wipe out the population one year there are more cysts to hatch the following year.

If you are lucky enough to have a vernal pool near you with fairy shrimp, scoop some up and take a closer look. Use a loupe, or a hand lens, or zoom in with your phone camera.

Males are the ones with the long pale pink protuberances vaguely like elephant trunks. Females are in constant motion, with a belly full of small eggs. Be prepared to spend some time–they are mesmerizing, and it is hard to stop watching.

The fairy shrimp in the pond near me are Eubranchipus vernalis. It was last year near the end of April I made my unexpected discovery. This year I checked the pond regularly, and their first appearance was April 2. They may have been in the pond, but not at the depth I was collecting from. There are several vernal pools within a walk of my house, and after finding the fairy shrimp at the fire pond I started checking them all. Zilch. Guess there is no accounting for fairy shrimp taste. Pristine ponds with barred owls cruising by and a meadow of wildflowers at the edge apparently do not have the appeal of this old, man-made, glorified ditch, bordered by a busy road.

If you seek fairy shrimp, I can only say good luck. When I accidentally found them I had no idea how rare they are. When I shared the excitement of my discovery I found that several friends had been looking for fairy shrimp for years to no avail. As a naturalist who often hears about the most amazing fungus, or the rare sighting of a lynx, or the once-in-a-lifetime slime mold growth, but always seems to miss it, I am no stranger to feeling everyone sees the cool stuff but me. Be safe of course, but persevere. They are there and this is the season. Or just go looking for something else entirely–and they may find you.

If your curiosity leads you to learn more about fairy shrimp, get out and take a few dips at some vernal pools, but also go to http://www.vernalpools.me/wp-content/uploads/2018/03/OfPoolsAndPeople_ColoringBook.pdf which has all the information you may want about fairy shrimp and vernal pools, and points you to other sources if that is not enough. There is a kid-oriented coloring book about vernal pools, too, which is a fun learning tool for all ages and perfect for exploring the natural world from wherever you are.

Hope you get to see a fairy! Even if you don’t believe in magic, they are pretty magical.

Coloring page for female fairy shrimp


Karen O. Zimmermann

About Karen O. Zimmermann

Karen O. Zimmermann savors chance encounters with people throughout the state of Maine, and is endlessly delighted with the tales they have to share.