Parasite diversity of Norwegian lemmings (Lemmus lemmus)

The parasite diversity of Norwegian lemmings Lemmus lemmus was studied in n orthern Fennoscandia during a moderate population peak in 1997-98. Our aim was to study the parasites of lemmings in their normal mountainous habitats in anticipation of the next great lemming migration in northern Fennoscand ia into the coniferous taiga. The blood parasites (Hepatozoon, Trypanosoma and Bartonella) found, Frenkelia sp., which invades the brain tissue of the host, and the pulmonary fungus Chrysosporium (Emmonsia) sp., have been det ected previously in the Norwegian lemming, but an unknown fungus, and oocys ts of Eimeria in spp. have not been reported from L. lemmus before. The Nor wegian lemming was found to have an exceptionally species-poor helminth fau na. Only one species of cestode (Andrya sp.) occurring in lemmings at the a dult stage was found, and the cestodes of carnivores that commonly parasiti ze voles at the larval stage were totally absent. The distribution and abun dance of vectors, and sympatric definitive hosts of parasites are predicted to have a major role in determining the parasites that lemmings will encou nter during their mass movements in new habitats. However, it is predicted that parasitism by adult and larval helminths is not markedly affected by t he habitat change associated with the mass migration.