On some larval trematode parasites of the mussel (Mytilus edulis) and the cockle (Cardium edule). Part II

Publisher Website
Google Scholar
Abstract
This trematode was obtained from cockles brought up with mussels to the Conway Mussel Cleansing Station and also from cockles collected from several other localities on the Menai Straits. It was present in every cockle examined, a total of several thousand in all. It occurred as a brown mass of varying size situated immediately beneath the hinge and occupying a small wedge-shaped cavity which occurs there. It could be obtained by cutting away the hinge with a knife when the brown mass was exposed. The latter breaks up very easily on teasing and consists of numerous more or less oval thick-walled sporocysts loosely embedded in the tissue of the cockle. These sporocysts are colourless or slightly straw-coloured and immobile. They contain a varying number of cercariae and a considerable amount of granular brown material. The fully developed cercaria (Fig. 1) is transparent except for the excretory sacs, which are full of very highly refractive granules and appear dark. The maximum diameter of these granules has been put forward by Rothschild (1935) as a valuable diagnostic character; in this species it is 5μ. The cercariae are moderately active and survive some time in sea water after removal from the sporocyst. This trematode was found throughout the year.