The cladoceran crustacean Daphnia pulex is representative species bearing the ESD system. In the natural favorable environmental conditions, they produce female offspring by parthenogenesis. However, when adult female of D. pulex receives unfavorable environmental cues, they produce male offspring to alter their reproductive modes to sexual reproduction. Sexual fate of offspring in D. pulex WTN6 strain can be controlled by simply changing the day length conditions parent WTN6 strain produces female progeny reared under the long day condition (LD, 14 h light : 10 h dark), whereas male progeny were emerged under the SD condition (SD, 10 h light : 14 h dark). In this study, to understand the mechanisms involved in reception of primary environmental stimuli and its signaling cascades regulating JH pathway for male production, we screened differentially expressed genes in ovaries including maturing oocytes, and whole bodies of adult D. pulex WTN6 strain reared under LD (female-inducing), SD (male-inducing) and MF-treated (male-inducing) conditions by using RNA-seq analysis.