Oyster Gill Turbellaria
Category 4 (Negligible Regulatory Significance in Canada)
Common, generally accepted names of the organism or disease agent
Scientific name or taxonomic affiliation
Urastoma cyprinae and possibly other species of Turbellaria.
In the mantle cavity of Crassostrea virginica and various other bivalve species from Atlantic Canada, the Gulf of Mexico, and various bivalves from Europe. Similar turbellarians have been reported from the gills of giant scallops (Placopecten magellanicus) in Atlantic Canada.
Impact on the host
In Europe, U. cyprinae is reported as an opportunistic mantle inhabitant on the gills of bivalves, or free-living on muddy bottoms. Nevertheless, Robledo et al. (1994) reported pathology in the gills of mussels (Mytilus galloprovincialis) infested with U. cyprinae. In Atlantic Canada, large numbers can be present with no apparent host-response. Under adverse circumstances, however, numbers of U. cyprinae may reach levels believed to be detrimental to their hosts. Urastoma cyprinae occurs throughout the gill surface of C. virginica and is attracted by mucus that coats the gills of oysters. Urastoma cyprinae is believed to feed on the mucus secreted by its host and its presence alters the protease composition of gill mucus in C. virginica (both U. cyprinae and gill mucus actively secrete proteases). Endoscopic techniques were used to reveal that there is extensive contact between U. cyprinae and the gill tissues, especially along the basal food tract where the flow of mucus is most highly concentrated. Apparently, U. cyprinae is negatively phototactic and is more attracted to oysters when compared to other mollusc species such as mussels and clams (Brun et al. 1999).
An unidentified turbellarian infesting the gills of C. virginica from the western coast of Florida, USA elicited a light to moderate haemocytic response from the gills and were surrounded by a mucus coat. However, the prevalence of infection was low (1% to 4%) and the number of turbellaria per oyster were few suggesting that the turbellaria were more commensal than parasitic (Winstead et al. 2004).
Gross Observations: Small oval or pyriform turbellarians up to 2 mm long present on gill surfaces and between gill lamellae.
Whole Mounts: For species confirmation, stain with acetic acid alum carmine and mount in permount. Larger specimens can be imbedded in paraffin for sectioning as necessary.
Histology: Examine transverse sections though gill and palp area of oysters for cross-sections through turbellarians characterised by ciliated surfaces.
Methods of control
No known methods of prevention or control. Experimental results indicate that U. cyprinae are negatively phototatic and display a strong attraction to oyster tissue (especially gill tissue coated with mucus) and to phytoplankton. Oysters grown in suspension have lower levels of U. cyprinae than oysters grown on the bottom. Research suggests that a combination of warm temperatures and low salinity may be useful in eliminating U. cyprinae from infected oysters (Bataller and Boghen 1997). Because U. cyprinae is sufficiently large to be visible to the oyster consumer, investigations to eliminate them prior to marketing using short-term depuration methods based on salinity tolerances are being conducted (Boghen et al. 1999). Although not considered to be a oyster health problem, managers of areas currently free of these worms should prevent their introduction.
Bataller, E. and A.D. Boghen. 1997. Détermination de la zone de tolérance à la salinité du turbellarié Urastoma cyprinae à l'état libre et en association avec l'huître américaine Crassostrea virginica. Bulletin of the Aquaculture Association of Canada 97-2:60-62.
Boghen, A.D., N.T. Brun and E. Bataller. 1999. The association between the turbellarian Urastoma cyprinae and the eastern oyster Crassostrea virginica. Journal of Shellfish Research 18: 296. (Abstract).
Brun, N.T., A.D. Boghen and J. Allard. 1996. Chemotactic responses by the turbellarian Urastoma cyprinae to different stimuli. Bulletin of the Aquaculture Association of Canada 96-3: 56-58.
Brun, N.T., A.D. Boghen and J. Allard. 1997. The possible role of mucus in the feeding behavior of the turbellarian Urastoma cyprinae in the oyster Crassostrea virginica. Bulletin of the Aquaculture Association of Canada 97-2:63-65.
Brun, N.T., A.D. Boghen and J. Allard. 1998. Studies of the turbellarian Urastoma cyprinae in relation to the presence of mucus on the gills of oysters Crassostrea virginica. Bulletin of the Aquaculture Association of Canada 98(2): 71-72.
Brun, N.T., A.D. Boghen and J. Allard. 1999. Distribution of the turbellarian Urastoma cyprinae on the gills of the eastern oyster Crassostrea virginica. Journal of Shellfish Research 18: 175-179.
Brun, N.T., A.D. Boghen and J. Allard. 1999. The presence of the turbellarian Urastoma cyprinae from different areas of the gills of the eastern oyster Crassostrea virginica. Journal of Shellfish Research 18: 291. (Abstract).
Brun, N.T., A.D. Boghen and J. Allard. 1999. Attraction of Urastoma cyprinae (Turbellaria: Urastomidae) to the eastern oyster Crassostrea virginica. Diseases of Aquatic Organisms 37:139-144.
Brun, N.T., N.W. Ross and A.D. Boghen. 2001. Biochemical changes in oyster gill mucus proteases in response to the turbellarian Urastoma cyprinae. In: Hendry, C.I. and S.E. McGladdery (eds), Aquaculture Canada 2000 - Proceedings of the 17th Annual Meeting of the Aquaculture Association of Canada, Moncton, May 28-31 2000. Aquaculture Association of Canada Special Publication No. 4, pp. 118-121.
Burt, M. D. B. and R. E. Drinnan. 1968. A microturbellarian found in oysters off the east coast of Prince Edward Island. Journal of the Fisheries Research Board of Canada 25: 2521-2522.
Cannon, L. R. G. 1986. Turbellaria of the World - A Guide to Families and Genera. Queensland Museum, Australia. 132 p.
Fleming, L. C. 1986. Occurrence of symbiotic turbellarians in the oyster, Crassostrea virginica. Hydrobiologia 132: 311-315.
Fleming, L. C., M. D. B. Burt and G. B. Bacon. 1981. On some commensal Turbellaria of the Canadian east coast. Hydrobiologia 84: 131-137.
Plourde, S. M., A. D. Boghen and J. Allard. 1991. Incidence of the turbellarian, Urastoma cyprinae, in the oyster Crassostrea virginica. Bulletin Aquaculture Association Canada 91-3: 72-73.
Robledo, J.A.F., J. Cáceres-Martínez, R. Sluys and A. Figueras. 1994. The parasitic turbellarian Urastoma cyprinae (Platyhelminthes: Urastomidae) from blue mussel Mytilus galloprovincialis in Spain: occurrence and pathology. Diseases of Aquatic Organisms 18:203-210.
Winstead, J.T., A.K. Volety and S.G. Tolley. 2004. Parasitic and symbiotic fauna in oysters (Crassostrea virginica) collected from the Caloosahatchee River and estuary in Florida. Journal of Shellfish Research 23: 831-840.
Bower, S.M. (2009): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Oyster Gill Turbellaria.
Date last revised: July 2009
Comments to Susan Bower
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