[Post-embryonic differentiation of a cutaneous electro-receptor].

In order to decrease the rate of postembryonic development of electroreceptor organs, excisions of epidermis and deafferentations were carried out in the gymnotid fish Eigenmannia virescens. Twenty-five days later, the epidermis showed electroreceptor organs without innervation. Some of these at the beginning of their development consisted of masses of identical cells, whereas others showed presumed sensory cells whose cytoplasm contained rudimentary synaptic structures. The epidermis also showed differentiated tuberous organs with a low number of sensory cells. In all these organs, radioactive thymidine was fixed in the nuclei of the platform accessory cells. Thirty-five-40 days after surgery, tuberous organs were identical to the functional organs, and thymidine was detected in the nuclei of the cavity accessory cells. These results show that the gymnotid electroreceptor organs can develop before any nervous contact occurs, and suggest that they might originate from epidermal cells.