A remarkable, precisely timed release of hyperglycemic hormone from endocrine cells in the gut is associated with ecdysis in the crab Carcinus maenas

Molting or ecdysis is the most fundamentally important process in arthropod life history, because shedding of the exoskeleton is an absolute prerequis ite for growth and metamorphosis. Although the hormonal mechanisms driving ecdysis in insects have been studied extensively, nothing is known about th ese processes in crustaceans. During late premolt and during ecdysis in the crab Carcinus maenas, we observed a precise and reproducible surge in hemo lymph hyperglycemic hormone (CHH) levels, which was over 100-fold greater t han levels seen in intermolt animals. The source of this hormone surge was not from the eyestalk neurosecretory tissues but from previously undescribe d endocrine cells (paraneurons), in defined areas of the foregut and hindgu t, During premolt (the only time when CHH is expressed by these tissues), t he gut is the largest endocrine tissue in the crab. The CHH surge, which is a result of an unusual, almost complete discharge of the contents of the g ut endocrine cell, regulates water and ion uptake during molting, thus allo wing the swelling necessary for successful ecdysis and the subsequent incre ase in size during postmolt, This study defines an endocrine brain/gut axis in the arthropods. We propose that the ionoregulatory process controlled b y CHH may be common to arthropods, in that, for insects, a similar mechanis m seems to be involved in antidiuresis. It also seems likely that a cascade of very precisely coordinated release of (neuro) hormones controls ecdysis .