A new species of planktonic rotifer, Keratella sinensis n.sp. is descr
ibed from Lake Yaoquan, Heilongjiang, P.R. China. It probably also occ
urs in the Republic of Korea and Japan. The new morphospecies is chara
cterised by an unusually smooth lorica, and strongly reduced lateral a
nterior spines. It is the first example of a planktonic freshwater rot
ifer, endemic to North East Asia.