STUDY OF MICROPHALLIDAE (TREMATODA) .51. ON 5 SPECIES FOUND IN THE COMMON LOON, GAVIA-IMMER (AVES), IN THE UNITED-STATES, INCLUDING MICROPHALLUS-FORRESTERI N-SP - LIKELY PLURALITY OF THE SPECIES MICROPHALLUS-NICOLLI (CABLE AND HUNNINEN, 1938)

The authors describe and illustrate five species of Microphallid trema todes from the intestine of Gavia immer (Aves: Gaviiformes) from the s outhern coast of the United States (Florida). Microphallus forresteri n. sp. is 500-700 mu m long with a symmetrical, regularly ovoid male p apilla with a length (60 x 43 mu m) close to the acetabular diameter a nd a broad ejaculatory canal centred along its longitudinal axis. A se cond species of Microphallus is determined as M. nicolli (Cable & Hunn inen, 1938). A metacercaria from the Pacific coast of North America, M . nicolli (sensu Young, 1949), appears to be a different species. Micr ophallus sp. ?nicolli of Anantaraman & Subramoniam (1976) from the Ind ian region is elevated to specific rank as M. selector n. sp, owing to its particular biology. A third species of Microphallus from Gavia, 4 00 mu m long and with a short conical male papilla (13 x 14 mu m), int ermediate between the papilla of M. nicolli and M. limuli, was not det ermined to species. A species of Maritrema 380 mu m long identified as Maritrema sp. of Harkema & Miller (1962) is also found in mammals fro m tidal marshes in the same geographical area. A second Maritrema sp., 750 mu m long with an annular arrangement of vitelline follicles, is ascribed to the Eroliae Group of Maritrema.