Crayfish plague

Crayfish plague (Aphanomyces astaci) is a water mold that infects crayfish, most notably the European Astacus which dies within a few weeks of being infected. When experimentally tested, species from Australia, New Guinea and Japan were also found to be susceptible to the infection.[2]

Crayfish plague
Scientific classification Edit this classification
Kingdom: Chromista
Phylum: Oomycota
Order: Saprolegniales
Family: Leptolegniaceae
Genus: Aphanomyces
Species:
A. astaci
Binomial name
Aphanomyces astaci
Schikora, 1906 [1]

History

Crayfish plague first arrived in Europe in Italy in 1859, either with imported crayfish from North America,[3] or in ballast water discharge.[4] After its original introduction in Italy in 1860, it spread quickly through Europe and was discovered in Sweden in 1907, in Spain in 1972, in Norway in 1971, in Great Britain in 1981, in Turkey in 1984 and in Ireland in 1987.

In 1959, to bolster dwindling stocks of native crayfish, the signal crayfish was introduced to Sweden.[3] The signal crayfish was known to be resistant, and it was not recognised at that time that it was a carrier of the disease.[3] After 150 years of contact, no resistance has been discovered in native European crayfish.[5]

This species was studied and named by the German Mycologist Friedrich Schikora (1859–1932), from a type specimen in Germany in 1906.

Transmission
Signal crayfish, rear view, from Grand Union Canal near its inflow/overflow with the River Nene.

Transport of signal crayfish, red swamp crayfish and infected native European freshwater crayfish between waters is the main cause of contamination, though the disease can also be spread via items that have been in contact with contaminated water, such as a fishing tackle or footwear.[6] The spores are sensitive to high or low temperatures. Most authorities have local rules and regulations to minimize the movement of water between different waterbodies (in for example a boat), and recommend that crayfish used as bait should come from the same water as that being fished, or should be frozen to at least −10 °C (14 °F) for one day before use, if there is a risk of contamination. The spores of crayfish plague disappear from an infected water system (connected lakes and rivers) within a few weeks once the last infected crayfish is removed.[6] Reintroduction is then possible, as long as no infected waters are in contact with the lake.

Signs

Infection with Aphanomyces astaci is accompanied by few signs in its early stages, and the first indication of infection may be mortality.[7] In the later stages, the muscles of the tail may appear whitened, or brownish-red where blood cells have encapsulated the hyphae. The effects of the neurotoxins in the oomycete can include appearing in daytime (crayfish are typically nocturnal) and a lack of coordination.[7]

References
  1. Paul Kirk (2010). "Aphanomyces astaci Schikora, 1906". World Register of Marine Species. Retrieved June 29, 2011.
  2. Susan M. Bower (June 28, 2006). "Crayfish plague (fungus disease)". Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish. Fisheries and Oceans Canada. Archived from the original on December 12, 2008. Retrieved June 29, 2011.
  3. Christian Nellemann & Emily Corcoran, ed. (2010). "Restoration of a depleted crayfish fishery in Europe – lessons learnt". Dead Planet, Living Planet: Biodiversity and Ecosystem Restoration for Sustainable Development (PDF). UNEP / Earthprint. pp. 90–91. ISBN 978-82-7701-083-0. Archived from the original on 2017-02-07. Retrieved 2011-06-29.
  4. Kei Westman (2002). "Alien crayfish in Europe: negative and positive impacts and interactions with native crayfish". In Erkki Leppäkoski, Stephan Gollasch & Sergej Olenin (ed.). Invasive Aquatic Species of Europe: Distribution, Impacts, and Management. Springer. pp. 76–95. ISBN 978-1-4020-0837-5.
  5. David Alderman (December 18, 2006). "Aphanomyces astaci" (PDF). Delivering Alien Invasive Species Inventories for Europe. Archived from the original (PDF) on September 24, 2015. Retrieved June 29, 2011.
  6. "Crayfish plague". Environment Agency. June 2, 2011. Archived from the original on September 21, 2008. Retrieved June 29, 2011.
  7. Nicky Buller (September 2008). "Crayfish Plague" (PDF). Australia and New Zealand Standard Diagnostic Procedure. Sub-Committee on Animal Health Laboratory Standards. Archived from the original (PDF) on 2015-03-11. Retrieved 2015-06-26.
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