The brain and the thoracic ganglion of a crustacean can synthesize and secrete gonad-stimulating hormone(GSH)which stimulates the maturation of gonad.In the previous experiments,sex steroid hormones(estradiol,testosterone,progesterone,etc.)have been detected from the crustacean.However,the feedback regulation of sex steroid hormones on the brain and the thoracic ganglion of the crustacean has not been reported so far.In the present experiment,monoclonal antibodies were applied to investigate the immuno-recognition of estrogen receptor(ER)and androgen receptor(AR)in the brain and the thoracic ganglion mass of Scylla paramamosain.The results showed that the distribution of the immunopositive substances of ER and AR was extremely similar.They distributed in the protocerebrum,deutocerebrum and tritocerebrum of the brain,and mainly in protocerebrum.In the thoracic ganglion mass,immuno-positive substances distributed in the subesophageal ganglion,thoracic ganglion and abdominal ganglion,and mostly in subesophageal ganglion.Immunopositive substances of ER and AR mostly existed in the cytoplasm of neurons.The present study will provide mor-phological evidence for the origin and the evolution of ER and AR.In addition,the immunoreactivities of ER and AR suggested that the estrogen and androgen may be involved in the feedback regulation of crustacean neuroendocrine. The brain and the thoracic ganglion of a crustacean can synthesize and secrete gonad-stimulating hormone (GSH) which stimulates the maturation of gonad. The previous experiments, sex steroid hormones (estradiol, testosterone, progesterone, etc.) Have been detected from the crustacean. However, the feedback regulation of sex steroid hormones on the brain and the thoracic ganglion of the crustacean has not been reported so far.In the present experiment, monoclonal antibodies were applied to investigate the immuno-recognition of estrogen receptor (ER) and androgen receptor (AR) in the brain and the thoracic ganglion mass of Scylla paramamosain. The results showed that the distribution of the immunopositive substances of ER and AR was similar. They distributed in the protocerebrum, deutocerebrum and tritocerebrum of the brain, and mainly in protocerebrum. the thoracic ganglion mass, immuno-positive substances distributed in the subesophageal ganglion, thoracic ganglion and abdominal ganglion, and mostly in subesophageal ganglion. Immunopositive substances of ER and AR mostly existed in the cytoplasm of neurons. The present study will provide mor-phological evidence for the origin and the evolution of ER and AR. addition, the immunoreactivities of ER and AR suggested that the estrogen and androgen may be involved in the feedback regulation of crustacean neuroendocrine.