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Diseases of Aquatic Organisms

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DAO 34:63-70 (1998)  -  doi:10.3354/dao034063

Infection characteristics of Himasthla elongata cercariae in cockles as a function of water current

X. de Montaudouin1,*, A. M. Wegeberg2, K. T. Jensen2, P. G. Sauriau3

1Laboratoire d'Océanographie Biologique, UMR 5805 Université Bordeaux 1 - CNRS, 2 rue du Pr Jolyet, F-33120 Arcachon, France
2Department of Marine Ecology, Institute of Biological Sciences, University of Aarhus, Finlandsgade 14, DK-8200 Aarhus N, Denmark
3CREMA (CNRS-IFREMER), BP 5, F-17137 L'Houmeau, France

ABSTRACT: Digenean trematodes are widespread parasites of marine fauna. The first intermediate host of Himasthla elongata (Echinostomatidae) is the periwinkle Littorina littorea. The second host is less specific, as it includes various bivalve species. The definitive host is a waterbird. The free-living cercaria acts to ensure transmission from the first and second intermediate hosts. We examined the impact of water flow (still and running water) and host size (6-8, 8-10, 10-12 mm shell length classes) on the settling success of H. elongata cercariae in the second intermediate host by utilizing the common cockle Cerastoderma edule. Under 2 scenarios (free-stream velocity of 0 and 6 cm s-1) more than 90% of the experimental population of cockles (90 individuals per replicate) acquired infections and 60% of the added cercariae were recovered as metacercariae in cockle tissue (mainly foot and siphons). Infection intensity increased significantly with cockle size. Considering the filtering capacity of cockles, the dimension of the flume, and the flow velocity, a passive infection mechanism is proposed based on the suspension feeding activity of the host organism. The scale of potential dispersal of H. elongata is at least a few hundred metres.

KEY WORDS: Cerastoderma edule · Cercariae · Dispersion · Flume · Himasthla elongata · Metacercariae · Transmission efficiency · Trematode

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