Biology:Ephippia

Short description: Eggs of small crustacea

Resting egg pouch (ephippium) and the juvenile daphnid that just hatched from it

Female Daphnia longispina carrying a resting egg (ephippium). The two dark, oval spots on the ephippium mark the places where the two resting eggs are located. The female was collected in a rock pool in south-western Finland. The animal is about 2 mm long.

Ephippia (singular: ephippium) are winter or dry-season eggs of the various species of small crustacean in the order Cladocera (within the Branchiopoda); they are provided with an extra shell layer, which preserves and protects the resting stages inside from harsh environmental conditions until the more favorable times, such as spring, when the reproductive cycle is able to take place once again. Ephippia are part of the back of a mother carrying them until they are fully developed. After molting, the ephippium stays in the water, or in the soil of dried puddles, small ponds, and vernal pools. The resting stages are often called eggs, but are in fact embryos with arrested development. Ephippia can rest for many years before the embryo resumes development upon an appropriate hatching stimulus.

See also

• Bythotrephes longimanus (invasive species)
• Cercopagis pengoi (invasive species)
• Daphnia
  • Daphnia longispina
  • Daphnia lumholtzi (invasive species)
  • Daphnia magna (large species)
  • Daphnia pulex (small, most common)
• Moina (smallest)

Further reading

• Ebert, D. (2005). Ecology, epidemiology and evolution of parasitism in Daphnia. Bethesda (MD): National Library of Medicine (US), National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/books/NBK2036/?term=Ebert. 
• Lampert, W. (2011). Daphnia: development of a model organism in ecology and evolution. Oldendorf/Luhe: Internat. Ecology Inst.. 
• Smirnov, N. N. (2014). The physiology of the Cladocera. Academic Press, Amsterdam. 
• Frederick Schram (1986). Crustacea. Oxford University Press. ISBN 978-0-19-503742-5.