Putative Molt-Inhibiting Hormone in Larvae of the Shore Crab Carcinus maenas L.: An Immunocytochemical Approach.

Immunocytochemical investigations of the eyestalk of Carcinus maenas zoeal larval stages, using an antiserum directed against putative Carcinus molt-inhibiting hormone (MIH), revealed immunopositive neuronal structures. These structures included perikarya associated with the medulla terminalis X-organ, parts of the sinus gland tract, and the neurohemal organ--the sinus gland. Apart from an increase in volume of the sinus gland between zoeal stage I and II, no striking changes in the topography or morphology of the MIH neurosecretory system were observed. Immunopositive structures were found in similar locations to those seen in adult crabs. Our results suggest that the control of molting by MIH in crustacean larvae may be similar to the currently accepted model of molt control in adult decapod crustaceans.