Freshwater zooplankton Daphnia can release two kinds of chemical cues; "kairomone", inducing polymorphology in green algae Scenedesmaceae, and "crowding chemicals", suppressing the population size of Daphnia itself through changing individual life history. The kairomone has already identified as aliphatic sulfates, whereas the crowding chemicals are still unknown. In the present study, we evaluated the dose-dependent effect of the info-chemicals released from Daphnia galeata, by analyzing the individual responses (changes in life history traits, population growth rate, and morphology) under differently conditioned D. galeata culture water. To adjust content levels of info-chemicals, the culture water of D. galeata at 25 inds L-1 (generally lower than active-level density of crowding chemicals) was concentrated up to 200 inds L-1 by a solid-phase extraction. The green alga Desmodesmus subcapitata was exposed to the culture water to check the activity of info-chemicals as the kairomone. In the experiment, we always detected morphological changes in D. subcapitata. On the other hand, D. galeata gradually responded to the conditioned water along the content levels of info-chemicals. Our results suggest two possibilities; (1) the kairomone at high concentration exert as the crowding chemicals, or (2) the crowding chemicals are generally released from Daphnia but only work at high concentration.