Chromosomes of Phagocata kawakatsui and Bdellocephala annandalei from LakeBiwa-ko in Honshu, central Japan

Two lake-dwelling species of paludicolen triclads from Lake Biwa-ko (Honshu , Japan) were studied taxonomically and karyologically. (1) Phagocata kawak atsui Okugawa, 1956, is an epigean species usually inhabiting shallow sprin gs and spring-fed streams in Central Japan. In Lake Biwa-ko, animals were o btained from several bottom stations of the littoral area in the southern p art of the northern basin (3-70 m in depth). Chromosome numbers and karyoty pe: 2x=24 (2m+2sm+2sm+2m+2sm+2m+2sm+2m+2m+2sm+2m+2m). The first pair of met acentric chromosomes is very large in size. (2) Bdellocephala annandalei Ij ima et Kaburaki, 1916, an endemic species, is distributed widely in the dee p areas of the northern basin (30 to over 100 m in depth). Chromosome numbe rs and karyotype: 2x=28 (2m+2sm+2sm+2sm+2sm+2m+2m+2m+2m+2m+2m+2m+2m+2m) wit h the first pair of metacentric chromosomes very long.