STUDIES ON THE TREMATODE GENUS PARAMONOSTOMUM LUHE, 1909 (DIGENEA: NOTOCOTYLIDAE) x HORACE W. STUXKARD The American Museum of Natural History, Central Park West at 79th Street, Nciv York, Netv York 10024 The genus Paramonostomum was erected by Liihe (1909) with Monostoma alveatum Mehlis in Creplin, 1846 (syn. Monostoma aheifonnc Cohn, 1904) as type. The species had been included by Monticelli (1892) in the genus Notoco-tylus Diesing, 1839, but Liihe predicated that it is not congeneric with Notocotyhts triserialls Diesing, 1839, type of Notocotylus. The species, P. alveatum, has been reported from a large number of birds including Anas spp., Anser anser, Nyroca marilla, Oedemia spp., Somateria mollissima, Cygnus spp., Branta spp., and Clan-yula hyemalis. Some 20 additional species of Paramonostomum have been de-scribed but distinctions between certain of them are very tenuous. One life-cycle, that of P. alveatum, was reported by Kulachkova (1954). The work was done at the marine station on Kandalaska Bay, in the southwest portion of the White Sea, longitude 33 East and latitude 65.5 North. Hydrobia ulvae was the intermediate host and harbored the asexual generations of the parasite. Mme. Kulachkova published two short papers (1961a, 1961b) on seasonal infec-tion of the mollusks and on the biology of the larval stages of P. alveatum. I am indebted to Dr. GaltsofT, who graciously translated the Russian texts for me. The studies of Mme. Kulachkova were occasioned by the mass mortality of young eider ducks; in the period 22 June to 7 July, 1949, 321 chicks died from the infection. As many as 50,000 worms were found in a single bird. The parasites penetrated between the intestinal villi, with inflammation and destruction of the epithelium and membranes. Fourteen per cent of the H. ulvae in the tide-pools were infected and the cercariae, on emergence, encysted promptly on the shells of the snails from which they had emerged. The cysts were 0.155 mm. in diameter and the worms matured in 6-8 days in the birds. The tide-pools had sandy-gravelly bottoms and the eider chicks, less than two weeks old, fed in these tide-pools where the shells of the hydrobias carried from 10 to 25 cysts per snail. Birds older than two weeks, fed in Fucus and mussel beds where the hydrobias were rare or absent, and birds older than two weeks survived. In the examination of 5427 snails over a four-year period, the rate of infection varied from 3.3% to 12%, with the greatest incidence in July and August. Shedding of the larvae began at water tempera-ture of 23 and massive discharge in the range 23 to 26. This was usually in the last week of June and first 10 days of July, although the dates varied with weather conditions, but this was the time when the eider chicks were feeding in the tide-pools. 1 Investigation supported by NSF, GB-3606, continuation of G-23561. 133
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