Animal Diversity Web

Geographic Range

Fairy shrimp are found in vernal pools across the northeastern United States, typically spanning east of the Appalachians from South Carolina up to Maine. They are also found in Ohio, Michigan, Indiana, Alabama, and southwestern parts of Ontario, Canada. (Belk, et al., 1998; Bodie and Semlitsch, 1998; Dexter, 1946; Ferguson, 1939; Hay and Hay, 1889; McCafferty, et al., 2010)

• Biogeographic Regions
• nearctic
  • native

Habitat

Fairy shrimp are freshwater organisms found in small vernal pools isolated from other bodies of water, which usually dry up during the summer months. Suitable pools must be deep enough so that they don't freeze all the way through during winter months, which would kill the developing young. Fairy shrimp are also rarely found in water warmer than 20°C. The cyst-like eggs of fairy shrimp are very robust and can be transported by the wind (if the pool has dried up) or other organisms to other pools before hatching but, once hatched, young are confined to one pool. Vernal pools are suitable habitats for fairy shrimp because they usually lack predatory fish. (Dexter, 1946; Ferguson, 1939; Hay and Hay, 1889; Knight, et al., 1975; McCafferty, et al., 2010; Weaver, 1943)

• Habitat Regions
• temperate
• freshwater

• Aquatic Biomes
• temporary pools

Physical Description

Fairy shrimp are bilaterally symmetrical organisms with 20 body segments, from which 10 pairs of leaf-like swimming appendages (phyllopods) extend. The head is distinct from the thorax and has a pair of compound eyes. The segments posterior to the thorax form an elongated tail, the last segment of which bears an additional pair of phyllopodia. Individuals are most typically orange but may be translucent/white, blue, or green (depending on diet). Juveniles are similar in morphology to adults but are more orange in color. Males are typically larger than females with orange bodies and swimming appendages. They have a set of claspers emerging from around the head which are used for mating purposes. Females have much smaller heads than males and a smaller second set of antennae. Females also have an ovisac located below their swimming appendages. ("Fairy Shrimp", 2012; Dexter, 1946; Ferguson, 1939; )

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

• Range length

  10 to 25 mm

  0.39 to 0.98 in

• Average length

  23 mm

  0.91 in

Development

Fairy shrimp eggs hatch and larvae begin to develop in the winter after pools in which they were laid fill back up with water; development continues until the pond begins to freeze again. After ponds melt in the spring, larvae undergo a series of molts and instars, adding body segments with each successive stage. Adult fairy shrimp have 20 body segments. Individuals grown in the lab at 6.5°C were reported to have an average growth rate of 0.13 mm per day. ("Fairy Shrimp", 2012; Castle, 1938; Dexter, 1946; Ferguson, 1939; Hay and Hay, 1889; Modlin, 1982; Prophet, 1963; Weaver, 1943)

• Development - Life Cycle
• diapause

Reproduction

Only one male and one female will mate at a time and males die shortly after copulation is completed. Little research has been done specifically on fairy shrimp mating behavior, but the behavior of a close relative, neglected fairy shrimp (Eubranchipus neglectus), has been better described. When males find females to mate with, they position themselves to use their claspers (on the second set of antennae) to grab on to females and inject their sperm. Although the mating process takes only minutes, males and females may remain clasped together for days. Males show a preference for larger females, likely due to their higher reproductive potential. ("Fairy Shrimp", 2012; Belk, et al., 1998; Feigenbaum and Switzer, 2007)

• Mating System
• polyandrous

In years when the vernal pools refill with water later in the year (sometimes as late as March), female shrimp can become sexually mature in as little as two weeks after hatching. Females are considered sexually mature when they have eggs in their brood pouch, whereas the males must have well-developed claspers. Adult fairy shrimp are active during the spring. Breeding occurs once a year, typically in April and May, before pools dry up (at which time mature individuals die). Once they mate, females release their eggs into the water where they settle at the bottom of the vernal pool, typically lying dormant until October or November when the pools fill back up with water. There is debate in the literature as to whether fairy shrimp eggs must go through a period of desiccation and/or freezing before they are able to hatch. It has been documented that, in order to hatch in the wild, fairy shrimp eggs require a resting period of at least a few months. Eggs can, however, lie dormant for years if necessary. Females have been reported to produce between 22 and 44 eggs per clutch. Eggs may have thinner shells ("summer eggs") or thicker shells ("winter eggs"); eggs with thinner shells will typically hatch during the same season that they were laid while those with thicker shells will overwinter. It has been suggested that females are more likely to lay "summer eggs" when there is a shortage of males in the population. ("Fairy Shrimp", 2012; Avery, 1939; Brendonck, 1996; Dexter, 1946; Eldridge, 1990; McCafferty, et al., 2010; Modlin, 1982)

• Key Reproductive Features
• semelparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous

• Breeding interval

  Fairy shrimp breed once yearly.

• Breeding season

  Fairy shrimp breed in the spring (March-May)

• Range number of offspring

  22 to 44

• Average number of offspring

  38

• Range age at sexual or reproductive maturity (female)

  14 (low) days

• Average age at sexual or reproductive maturity (female)

  45 days

• Average age at sexual or reproductive maturity (male)

  45 days

Female fairy shrimp spend time and energy developing the eggs before fertilization. There is no parental investment following egg laying as males die shortly after mating and females die when their vernal pools dry up. Eggs hatch and young develop after pools have filled again, without any parental care. (Avery, 1939; Dexter, 1946; Ferguson, 1939; Hay and Hay, 1889)

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female

Lifespan/Longevity

The lifespan of this species depends on environmental conditions. Fairy shrimp require water to stay alive and thus can only survive for as long as the vernal pools they inhabit remain filled. Vernal pools usually completely dry up by April or May, although some pools can stay filled for years at a time. Eggs do not hatch until the vernal pools are filled with water again, usually in October or November. Water temperature is another important factor determining life span; it has been observed, both in the wild and lab, that fairy shrimp can only survive for a few days in water warmer than 20-21°C. (Dexter, 1946; Ferguson, 1939; Knight, et al., 1975; Modlin, 1982)

• Typical lifespan
  Status: wild

  0.5 to 6 months

• Typical lifespan
  Status: captivity

  21 to 70 days

Behavior

Fairy shrimp are benthic, meaning that individuals spend the majority of their time on the bottom of their vernal pools. They are not generally very active and this, along with their coloration, can make them very hard to see. On cloudy days, they tend to remain near the bottom of the pools whereas on sunny days they can be found swimming near the top more frequently. They swim, ventral side up, by moving their appendages and, even when swimming, do not move very quickly. ("Fairy Shrimp", 2012; Dexter, 1946; Ferguson, 1939; McCafferty, et al., 2010; Modlin, 1985)

• Key Behaviors
• natatorial
• motile
• sedentary

Home Range

Once hatched, individuals' home ranges are limited to their isolated vernal pools. (Dexter, 1946; Hay and Hay, 1889; McCafferty, et al., 2010)

Communication and Perception

Individuals have a pair of compound eyes which they use to perceive their environments. Although no species-specific details were found, other anostracans are known to use chemorecption and mechanorecption to sense their environments and it is likely that this species does as well. (Tyson and Sullivan, 1979)

• Communication Channels
• visual
• chemical

• Perception Channels
• visual
• chemical

Food Habits

Fairy shrimp are benthic scrapers that use their appendages to scrape food off the bottoms of vernal pools, which is then filtered from the water. Their diet typically consists of benthic diatoms, filamentous algae (such as Draparnaldia glomer), desmids, platyhelminth eggs, and Arcella species. (Modlin, 1982; Modlin, 1985)

• Primary Diet
• carnivore
  • eats eggs
• herbivore
  • algivore
• omnivore
• planktivore

• Animal Foods
• aquatic or marine worms
• other marine invertebrates

• Plant Foods
• algae

• Foraging Behavior
• filter-feeding

Predation

This species is not usually food for other organisms because the vernal pools in which they live do not support predatory fish that will survive the seasonality of these pools. In the rare cases where fairy shrimp are found in pools that do not dry up every year, they may be prey to some fish. While current literature has not investigated this species as a prey item specifically, other species of fairy shrimp (Order Anostraca) are eaten by waterfowl in the spring, as well as some amphibians (wood frogs and mole salamanders, specifically) and insect larvae. ("Fairy Shrimp", 2012; Eldridge, 1990)

• Known Predators

  • Wood frog (Lithobates sylvaticus)
  • Caddisfly larvae (Order Trichoptera, Class Insecta)
  • Dytiscidae larvae (Order Coleoptera, Class Insecta)
  • Mole salamander (Genus Ambystoma, Class Amphibia)
  • Waterfowl (Class Aves)

Ecosystem Roles

The vernal pools in which these fairy shrimp are typically found contain a relatively high level of algae during the spring. Fairy shrimp are primarily algivores which may help to keep the relative levels of algae low. (Ferguson, 1939; Modlin, 1982; Modlin, 1985)

Economic Importance for Humans: Positive

This species does not have any major economic importance for humans.

Economic Importance for Humans: Negative

There are no known adverse effects of this species on humans.

Conservation Status

As it has very specific habitat requirements, the protection of small wetlands where vernal pools exist is essential to its survival. (Bodie and Semlitsch, 1998; )

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Contributors

Nicholas Kirkpatrick (author), University of Michigan-Ann Arbor, Alison Gould (editor), University of Michigan-Ann Arbor.

References

2012. "Fairy Shrimp" (On-line). Accessed December 07, 2012 at http://www.vernalpool.org/inf_fs.htm.

Avery, J. 1939. Effect of Drying on the Viability of Fairy Shrimp Eggs. Transactions of the American Mircroscopical Society, 58/3: 356.

Belk, D., G. Mura, S. Weeks. 1998. Untangling Confusion between Eubranchipus vernalis and Eubranchipus neglectus (Branchiopoda: Anostraca). Journal of Crustacean Biology, 18: 147-152.

Bodie, J., R. Semlitsch. 1998. Are Wetlands Expendable?. Conservation Biology, 12/5: 1129-1133.

Brendonck, L. 1996. Diapause, quiescence, hatching requirements: what we can learn from large freshwater branchiopods (Crustacea: Branchiopoda: Anostraca, Notostraca, Conchostraca). Hydrobiologia, 320: 85-97.

Castle, W. 1938. Hatching of the eggs of the "fairy shrimp". Science, 87/2267: 531.

Dexter, R. 1946. Further studies on the life history and distribution of Eubranchipus vernalis (Verrill). The Ohio Journal of Science, 46/1: 31-44.

Eldridge, J. 1990. "Waterfowl Management Handbook" (On-line). Fish and Wildlife Leaflet 13.3.3.. Accessed March 24, 2012 at http://www.nwrc.usgs.gov/wdb/pub/wmh/13_3_3.pdf.

Feigenbaum, C., P. Switzer. 2007. The Effect of Male and Female Body Size on the Mating Behavior of Male Fairy Shrimp, Eubranchipus neglectus. Journal of Freshwater Ecology, 22/2: 271-276.

Ferguson, M. 1939. Observations on Eubranchipus vernalis in southwestern Ontario and eastern Illinois. American Midland Naturalist, 22/2: 466-469.

Hay, O., W. Hay. 1889. A Contribution to the Knowledge of the Genus Branchipus. The American Naturalist, 23/266: 91-95.

Knight, A., R. Lippson, M. Simmons. 1975. The Effect of Temperature on the Oxygen Consumption of Two Species of Fairy Shrimp. American Midland Naturalist, 94/1: 236-240.

McCafferty, S., N. Warren, C. Wilbur, S. Shumway. 2010. Genetic Divergence Among Massachusetts Populations of the Vernal Pool Fairy Shrimp Eubranchipus vernalis (Crustacea: Anostraca). Northeastern Naturalist, 17/2: 258-304.

Modlin, R. 1982. A Comparison of Two Eubranchipus Species. American Midland Naturalist, 107/1: 107-103.

Modlin, R. 1985. A Comparison of the Gill Surface Areas of Two Sympatric Species of Fairy Shrimp (Anostraca, Crustacea). Freshwater Invertebrate Biology, 4/3: 138-142.

Prophet, C. 1963. Some factors influencing the hatching of anostracan eggs. Transactions of the Kansas Academy of Science, 66/1: 150-159.

Southwick, C., A. Reading, B. Sladen. 1964. Patterns of survivorship in laboratory populations of freshwater fairy shrimp, Eubranchipus vernalis (Verrill). American Midland Naturalist, 72/1: 133-141.

Tyson, G., M. Sullivan. 1979. Antennular Sensilla of the Brine Shrimp, Artemia salina. Biological Bulletin, 156/3: 382-392.

Weaver, R. 1943. Observations on the Life of Cycle of the Fairy Shrimp Eubranchipus vernalis. Ecology, 24/4: 500-502.

Wolfe, A. 2005. A histological and histochemical study of the male reproductive system of artemia (Crustacea, Branchiopoda). Journal of Morphology, 135/1: 51-69.