Many invertebrates go through a process called
ecdysis. Taken from the ancient Greek the word means, literally,
to strip off. It leaves behind an
exuviae (often spelled with the final
e omitted), the remains of the exoskeleton which has been shed, often with related structures still attached. For some invertebrates it can be a regular occurrence to facilitate growth. For others it can be part of a series of
instars which culminate in the emergence of the finished, adult form. It is a fascinating process where beauty can be found in the grotesque. For these animals, however, the process of growing up is far more than simply skin deep.
Essentially, ecdysis is the molting of the cuticle, the tough multi-layered cover outside the epidermis that provides protection as an exoskeleton. The exoskeleton must be shed as it constrains growth. First, the cuticle separates from the epidermis – yet the arthropod remains inside for now - this is called apolysis. Next, a hormone called ecdysone is secreted from the epidermis. It fills the gap between the old cuticle and the epidermis which is known as the exuvial space. The enzymes in the hormone are not activated until a new epicuticle (the outermost waxy layer of the arthropod exoskeleton) is formed. Once this is done they kick in and the lower regions of the old cuticle are digested. Finally the process of molting can start.
