A New Species of <i>Leptomonas</i> Parasitizing the Macronucleus of <i>Paramecium trichium</i>*

Abstract

SYNOPSIS. A leptomonad zooflagellate infecting the macronucleus of Paramecium trichium is described. The cell body of Leptomonas karyophilus n. sp. is 5μ long and the flagellum is 12μ long. There is a central ovoid nucleus, a bar‐shaped kinetoplast and a contractile vacuole. The flagellate undergoes division in the macronucleus, proliferating there until it has killed its host. Mildly infected paramecia are able to divide and if fed regularly can be maintained carrying the parasite. Cross infections with P. caudatum, P. bursaria and P. aurelia were successful to varying degrees.