Asellus aquaticus

Asellus aquaticus is a freshwater crustacean resembling a woodlouse. It is known by common names including "waterlouse", "aquatic sowbug" and "water hoglouse".

Asellus aquaticus
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Crustacea
Class:
Malacostraca
Order:
Isopoda
Family:
Asellidae
Genus:
Asellus
Species:
A. aquaticus
Binomial name
Asellus aquaticus

Ecology

Known as "cress bugs" to anglers, Asellus aquaticus is common throughout the temperate zone including Europe, Russia, and North America.[1] It is found in rivers, streams and standing water particularly where there are plenty of stones under which it hides although not where the water is strongly acidic.[2] It is a detritivore.

Asellus aquaticus is relatively tolerant of a range of pollutants and has been used as an indicator of water quality.[1]

Life Cycle and Reproduction

'Asellus aquaticus' can breed throughout the year, if the temperature is high enough: they do not breed under cold temperatures. Maturity can be reached in few months under warm summer temperatures, but maturation may take as much as two years in permanently cold water bodies (e.g., high-latitude or mountain waters).[3] Life span varies similarly: from 9 months in South Africa to 20 months in Northern Europe. Females carry eggs in brood pouches underneath their body.[4]

Aquarium Keeping

Aquarists worldwide are showing increasing interest towards asellus aquaticus as a low-maintainance freshwater aquarium pet and tank cleaner. While often sold as live food for other fish, some keepers in the US and Germany have started selectively breeding asellus aquaticus to be sold as pet, usually from online platforms like eBay.[5]

Conservation

A number of subspecies are considered to be endangered including:

  • Asellus aquaticus carniolicus, endemic to Slovenia.[6]
  • Asellus aquaticus cavernicolus found only in Italy and Slovenia.[7]
  • Asellus aquaticus cyclobranchialis, endemic to Slovenia.[8]

References
  1. Lorraine Maltby (1991). "Pollution as a probe of life-history adaptation in Asellus aquaticus (Isopoda)". Oikos. 61 (1): 11–18. JSTOR 3545402.
  2. Brian A. Whitton (1982). Rivers, Lakes and Marshes. London: Hodder & Stoughton. p. 131. ISBN 0-340-23155-6.
  3. Karen Anna Økland (1978). "Life history and growth of Asellus aquaticus (L.) in relation to environment in a eutrophic lake in Norway". Hydrobiologia. 59 (3): 243–259. doi:10.1007/BF00036504.
  4. P. Sterry (1997). Complete British Wildlife. Collins. p. 212. ISBN 0-583-33638-8.
  5. "List of online distributors of freshwater isopods worldwide". Shrimp Keep. Retrieved 22 May 2020.
  6. Boris Sket (1996). "Asellus aquaticus ssp. carniolicus". IUCN Red List of Threatened Species. 1996. Retrieved May 15, 2010.CS1 maint: ref=harv (link)
  7. Boris Sket (1996). "Asellus aquaticus ssp. cavernicolus". IUCN Red List of Threatened Species. 1996. Retrieved May 15, 2010.CS1 maint: ref=harv (link)
  8. Boris Sket (1996). "Asellus aquaticus ssp. cyclobranchialis". IUCN Red List of Threatened Species. 1996. Retrieved May 15, 2010.CS1 maint: ref=harv (link)
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