Turbellaria infestation of Crayfish
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Category
Category 4 (Negligible Regulatory Significance in Canada)
Common, generally accepted names of the organism or disease agent
Flatworm infestations, Turbellaria of crayfish, Temnocephalan infestation.
Scientific name or taxonomic affiliation
Scutariella didactyla and Temnocephala spp. and species in several other genera (e.g. Diceratocephala, Notodactylus, Craspedella) of Rhabdocoela in the Order Temnocephalida.
Geographic distribution
Predominantly in Australia, New Zealand and South America but some species also occur in India, Madagascar, Indonesia, New Guinea, the Philippines, Central America, North America (one species) and the Balkans.
Host species
Freshwater decapod crustaceans including numerous species of crayfish, notably in the family Parastacidae, as well as Macrobrachium spp., other shrimps and crabs.
Impact on the host
Temnocephalans normally inhabit the external surfaces, especially the crevices about the appendages, though some live in the branchial chamber or on the mouth parts. The diet of most species is the same as for free-living rhabdocoels except for S. didactyla which feeds on the host body fluids. Temnocephalan egg masses cemented to the host exoskeleton, as well as providing an ideal habitat for epibionts and a potential site of infection for pathogens, are unsightly and adversely effect marketing of commercial crayfish.
Diagnostic techniques
Gross Observations
Small (usually less than 5 mm long), flattened leech-like organisms with anterior tentacles and adhesive organ (generally at the posterior end) on the exoskeleton of crayfish.
Methods of control
These flatworms seem to have a low tolerance for high salinity. Submerging crayfish in a bath of 50 % seawater for 2-3 hours can be quite effective in destroying flatworms. In commercial aquaculture facilities, Cherax quadricarinatus, are submerged in 100 % seawater for 45 min. Also, a 15 min dip in 0.5 % formalin has been used to reduce flatworm infestations. Although these treatments are effective against the flatworms, the egg stage is much more resistant requiring that treatments be reapplied after the eggs have hatched.
References
Alderman, D.J. and J.L. Polglase. 1988. Pathogens, parasites and commensals. In: D.M. Holdich and R.S. Lowery (eds.). Freshwater Crayfish: Biology, Management and Exploitation. Timber Press, OR., p. 197-198.
Cannon, L.R.G. and K.B. Sewell. 1995. Craspedellinae Baer, 1932 (Platyhelminthes: Temnocephalida) ectosymbionts from the branchial chamber of Australian crayfish (Crustacea: Parastacidae). Memoirs of the Queensland Museum 38(2): 397-418.
Jennings, J.B. 1971. Parasitism and commensals in the Turbellaria. Advances in Parasitology 9: 1-32.
Jones, T.C. and R.J.G. Lester. 1993. Aspects of the biology and pathogenicity of Diceratocephala boschmai (Platyhelminthes; Temnocephala), an ectosymbiont on the redclaw crayfish Cherax quadricarinatus. Australian Journal of Marine and Freswater Research 44: 927-933.
Pearce, M.C. 1990. Redclaw diseases. In: C.C. Shelley and M.C. Pearce (eds.) Proceedings of the Seminar - Farming the Redclaw Freshwater Crayfish. Northern Territory Department of Primary Industry and Fisheries, Darwin, p 29-31.
Citation Information
Bower, S.M., Cannon, L.R.G. (1997): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Turbellaria infestation of Crayfish.
Date last revised: November 1997
Comments to Susan Bower
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