The relationship of three Brachionus calyciflorus morphotypes (two short-spined, single-spined and spineless ones) was studied in the laboratory. Newly hatched females of each morphotype were cultured individually in an inorganic or Asplanchna-conditioned mediums, and the morphotype of their offspring were checked at 200× magnification. Females of each morphotype, cultured in the inorganic medium, could produce offspring of these three morphotypes in a single generation. Females of all three morphotyes could respond to specific Asplanchna-substances when they were cultured in Asplanchna-conditioned medium. Moreover, we observed that these three morphotype females could coexist in the medium and had three types of egg-bearing females. Based on the above observations we suggest that B. calyciflorus was a morphotype complex and has three basic morphotypes.