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Aquaculture 182 2000 199–208 www.elsevier.nlrlocateraqua-online
Elimination of the gill worm Urastoma cyprinae ž
Graff from the eastern oyster Crassostrea ž
Õ irginica Gmelin using different
salinity–temperature combinations
Erick Bataller, Andrew D. Boghen
Department of Biology, UniÕersite de Moncton, Moncton, New Brunswick, Canada E1A 3E9
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Accepted 7 June 1999
Abstract
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Urastoma cyprinae Class: Turbellaria is a facultative parasite of the eastern oyster Cras- sostrea Õirginica. Because the worms are clearly visible when present in oysters, they could
conceivably have a negative impact on the lucrative half-shell oyster market. Our work examines the salinity and temperature tolerances of U. cyprinae to help formulate ways of eliminating the
parasite from oysters prior to marketing. Isolated worms were exposed to salinities of 0‰ to 55‰ at temperatures of 5
8C, 158C and 208C, and in infected oysters at salinities of 8‰, 28‰ and 55‰ at temperatures of 10
8C, 158C and 208C. Findings reveal that the salinity tolerance of isolated U. cyprinae ranges between 12‰ and 40‰. In the case of infected oysters, two scenarios for the
destruction of worms emanated: firstly, to depurate oysters for 2 days at a salinity and temperature of 55‰ and 10
8C, respectively, or, alternatively, to expose oysters to a salinity–temperature regime of 8‰ and 20
8C for 4 days. However, to eliminate all traces of dead worms from oysters, the optimal salinity–temperature combination was found to be 8‰ at 20
8C for 8 days. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Crassostrea Õirginica; Oyster; Urastoma cyprinae; Gill worm; Turbellarian; Salinity; Temperature; Depuration
1. Introduction
Ž Urastoma cyprinae is a Turbellarian belonging to the order Prolecithophora Holo-
. Ž .
coela Cannon, 1986 and has been reported from the gills of various bivalve species
Corresponding author. Fax: q1-5068584541. 0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved.
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PII: S 0 0 4 4 - 8 4 8 6 9 9 0 0 2 8 1 - 1
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Goggin and Cannon, 1989; Noury-Sraıri et al., 1990 . Murina and Solonchenko 1991
¨
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and Teia dos Santos and Coimbra 1995
suggested that the worm may provoke pathological changes in the mussels Mytilus edulis and Mytilus galloproÕinciallis. This
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was confirmed by Robledo et al. 1994 who demonstrated that U. cyprinae induces severe gill disruption in M. galloproÕincialis.
Ž In Canada, U. cyprinae was reported in the blue mussel M. edulis Fleming et al.,
. Ž
. 1981 . Burt and Drinnan 1968 described the worm from the gills and mantle of the
eastern oyster Crassostrea Õirginica sampled along the Atlantic coast and suggested that it was in all probability a facultative commensal.
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In their preliminary investigation, Plourde et al. 1991 raised the possibility that there may exist an inverse relationship between the number of worms and the physio-
logical condition of infected oysters. As part of a comprehensive oyster-monitoring Ž
. program, Boghen et al. 1993 reported high levels of infestation of the eastern oyster by
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U. cyprinae. More recently, Brun et al. 1999a conclusively showed that the worms were strongly attracted to oyster gill mucus, dispelling the likelihood that they were
simply facultative commensals. Aside from any potentially negative effects on oysters, the visible presence of the
worms on the gills, especially when occurring in the hundreds and even thousands, could contribute to a drop in demand by the lucrative half-shell market. Our work
examines the salinity and temperature tolerances of U. cyprinae to gain new insight into the biology of the worm, and help formulate ways of eliminating the parasite from
oysters.
2. Material and methods
