GENETIC-DIVERGENCE BETWEEN S-TYPE AND L-TYPE STRAINS OF THE ROTIFER BRACHIONUS-PLICATILIS MULLER,O.F.

Allozyme variation was determined for 67 strains of the rotifer Brachionus plicatilis O.F. Muller including 37 strains of S type and 30 strains of L type collected from all over the world, using horizontal starch gel electrophoresis. Six of the 18 enzymes assayed were variable, viz., lactate dehydrogenase (LDH), malate dehydrogenase (MDH), 6-phosphogluconate dehydrogenase (6PGD), superoxide dismutase (SOD), phosphoglucomutase (PGM) and glucose phosphate isomerase (GPI). 33 of the 46 alleles detected for the six loci were specific for either S or L type strains. On the basis of genetic distances calculated from allele frequencies of the 46 alleles, a dendrogram of the similarity among 67 strains was drawn. The strains were divided into two groups at a large genetic distance. One group consisted of 37 strains which coincided with the strains classified as S type in morphometric analysis. The other group consisted of 30 strains which coincided with ones classified as L type in morphometric analysis. The result indicates that the two groups of the rotifer, S and L, are genetically divergent.