Gonadotropinreleasing hormone(GnRH)is a kind of very important and crucial hormone in neuroregulation and reproduction.In order to elucidate whether the GnRH receptor exists or not,and to investigate its locations in the crustaceanpeculiar optic ganglion as well,the immunohistochemical technique of MaxVision^TM method was used in this study.The locations of immunoreactive substances in the optic ganglion of the female swimming crabs, Portunus trituberculatus were found out in different vitellogenesis stages.The results reveal that:the immunoreactive substances of GnRH receptor were widely detected in many parts of the optic ganglion of the female crabs,lamina ganglionaris(LG),medulla externa(ME),medulla interna(MI),medulla terminalis(MT)and X organ as well.And they were more strongly marked in the neurosecretory cells of ME,MI and X organ.In the optic ganglion of the female crabs in different vitellogenesis stages,the locations of immunoreactive substances of GnRH receptor were nearly the same,and there were also differences in the intensity of the immunoreaction.The results of this study,show that the immunoreactive substances of GnRH receptor existing in the optic ganglion of P. trituberculatus,can provide morphologic evidence for GnRH participating in the neuroendocrine regulation of the optic ganglion.