ABSTRACT
Our most detailed knowledge of cirripede endocrinology concerns the histology of neurosecretory centres and the processes that control moulting and egg hatching. Control of moulting in cirripedes is achieved in a similar way to that in other Crustacea, and involves ecdysteroids and a moult-inhibiting hormone. One ecdysteroid, 20-hydroxyecdysone, may have an additional role as a gonad inhibitor, although this view has been questioned.
The retention of juvenile characters by the cypris larva following metamorphosis from nauplius stage VI in the presence of a juvenile hormone or analogue suggests that larval moulting is controlled by such a hormone. However, juvenile hormone has not yet been demonstrated to occur naturally in barnacle larvae.
The control of the egg hatching in barnacles has received much attention. In Semibalanus balanoides*, a prostaglandin is released by the adult into its mantle cavity in response to feeding. This compound acts directly on the embryos, which respond by secreting dopamine. This causes vigorous muscular movements of the embryo to bring about hatching of the stage I nauplius larva. Synchrony between egg hatching and food supply indicates environmental control of an endocrine process.
The more detailed data on endocrine processes in other arthropods, particularly in the Malacostraca and the Insecta, can provide models upon which experimental studies of barnacle endocrinology may be based.
