2.1. Clam collection and maintenance
Clams (approx. 100) were collected in February 2019thfrom a sampling site H45 located in the Gulf of GdaƄsk (southern Baltic Sea) at 45m depth. The selected area has been reported to have the highest prevalence of DN in L. balthica , as described in: Smolarz et al. (2005bd) and Ogrodowczyk (2017) (Fig. 2.1 ). Clams exceeding 10 mm in size (large enough for haemolymph withdrawal) were selected from the sediment samples collected with a Van Veen grabber on board of the rv Oceanograf. Transport and laboratory set-up were adjusted to imitate in situ conditions. Bivalves were kept in 15 L tanks (approximately 50 clams per one tank) filled with seawater collected at sea bottom from the sampling site for time not exceeding five days. No sediment substrate was added to tanks with animals for purification purposes.