Limnological Institute, Russian Academy of Science, Siberian Branch, Irkutsk 664033, Russia

Abstract

Baikal planaria from genus Bdellocephala were typified using rDNA locus coding 5' - end domain of 18S ribosome RNA. Five colour forms of 24 possible variants that differ in diapason 0-1, 3% of genotype were determined by comparative analysis of nucleotide sequences. The authors use back colour - one of the most variable and typical character in the given group - to collect material for investigation. It allows to minimize the size of investigation sample and at the same time to cover maximum variability of Bdellocephala. One of the positive result of molecular typification of colour forms was a discovery of unique individuals that belong to new species. Karyological analysis of colour forms shows variations in chromosome numbers that divide planaria into 3 groups (2n=20, 24, 26). Comparative analysis of morphological and ecological characters and karyotypes of some forms united by the same genotype allows to distinguish them as separate species. Criteria of modern phenetic system of Baikal planaria are discussed.