Distribution of Trypetesa lampas (Cirripedia,Acrothoracica) in various gastropod shells

The distribution of Trypetesa lampas (Hanoock) and its rates of infection of different species of gastropod shells in the waters of Anglesey were studied. T. lampas was found in depths from 3 to at least 25 fathoms (5 to 46 m). It infected dead shells, mainly of Buccinum undatum L., Colus gracilis (da Costa), Neptunea antiqua (L.) and Natica alderi (Forbes); it was absent from shells occupied by hermit crabs in the intertidal zone. Significantly more B. undatum shells were infected than shells of N. antiqua and Natica alderi, and more of both C. gracilis and N. antiqua than of Natica alderi. Larger shells of B. undatum were more likely to be infected than were the smaller ones. The number of females per shell varied with the shell length raised to the power 2.39 instead of as expected with the square of the length.