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New Jersey Endangered and Threatened Species Field Guide
Eastern fairy shrimp
Species Group: Invertebrate
State: Special Concern
Fairy shrimp are small crustaceans only about an inch in length. They have a segmented body divided into three parts: head, thorax, and abdomen. Their exoskeleton is thin and flexible and they do not have a carapace. They have 11 pairs of leaf-like swimming legs known as phyllopodia with which they swim upside-down. Their color ranges in shades of gray, blue, green, orange, and red.
Fairy shrimp have two compound eyes on stalks and two pairs of antennae. The first pair of antennae are small. The second pair is longer and, in males, they are enlarged and specialized for holding the female during mating.
DISTRIBUTION AND HABITAT
The Eastern fairy shrimp is found in eastern North America, from Quebec in the north to Alabama in the south and as far west as Minnesota. The actual extent of its range, however, is not known. Although the species is known to occur in New Jersey, its range within the state is unknown.
Due to their relatively large size, slow movement, and lack of a hard shell, fairy shrimp are prey for many other animals. Because of this, they primarily inhabit vegetated vernal pools where there are fewer predators than in permanent water bodies and where fish cannot survive. They prefer clear cool to cold water with a neutral to low pH and they do not inhabit running water.
This species of fairy shrimp is a filter feeder which feeds on plankton and other small organic particles in the water.
Fairy shrimp have a life cycle specialized for living in their temporary vernal pool habitat. They are known as “fairy” shrimp due to the seemingly “magical” way in which they seem to appear out of nowhere in their woodland pools of water, often in locations where they have not been seen in years.
In New Jersey, fairy shrimp usually begin hatching between February and March. They may often be observed swimming under frozen water surfaces. They are sexually mature within 45 days and have a maximum lifespan of 70 days.
Females lay eggs which can withstand heat, cold, and dry conditions. These eggs are drought resistant and may survive several years without water. Fairy shrimp eggs have been known to survive for 15 years before hatching. Eggs overwinter in a dormant stage. Upon exposure to water, the eggs will soon come out of dormancy and will then hatch.
Fairy shrimp cannot tolerate warm water conditions and, in New Jersey, are usually not found within vernal pools after late May or whenever water temperatures reach 68-72° F.
CURRENT STATUS, THREATS, AND CONSERVATION
Fairy shrimp are an important food source for insects, amphibians, and waterfowl. They are also an indicator of water quality and aquatic ecosystem health. The filling-in or modification of wetlands which support vernal pools is the greatest threat to fairy shrimp in New Jersey because it results in loss or modification of pool ecosystems. Road run-off as well as pesticide, herbicide, fertilizer, and sediment run-off within watersheds may also harm fairy shrimp.
Over 300 species of fairy shrimp have been identified so far throughout the world with some known only from a single location. Some species are protected either at the federal level or by various states. A status review completed in 2010 by the New Jersey Endangered and Nongame Species Program found that the Eastern fairy shrimp should be listed as a species of special concern. This listing is due to increasing loss of vernal pool habitat within the state as well as the lack of information regarding their status within New Jersey. Much greater survey effort targeted at fairy shrimp species will be necessary in order to determine their distribution and abundance within New Jersey.
Text written by Michael J. Davenport in 2011.
Species: E. holmanii
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