Studies on the life-cycle of Microphallus pygmaeus (Levinsen, 1881) (Trematoda: Microphallidae)

Summary A description is given of the morphology, ecology and life-cycles of two forms of Microphallus pygmaeus (Levinsen, 1881), at Twr Gwylanod, Aberystwyth. The larval stages of the larger form occur in spent adult Littorina saxatilis tenebrosa and the adults in the herring gull, Larus argentatus argentatus. The larvae of the smaller form occur in juvenile L. saxatilis tenebrosa and the adults in the rock pipit, Anthus spinoletta. The domestic duckling may act as the experimental final host to both forms. There are no free-living stages and only one intermediate host in each life-cycle. The variations in percentage infection of the intermediate host by each form, with season, with height above chart datum and size of the host, are compared. The reasons for the observed differences and the taxonomic status of the two forms are discussed.