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Previous The laws of physics and inheritance. Next Molting and the exoskeleton: Squishy crabs. However, the exoskeleton is rigid and cannot expand.
Thus, when an arthropod grows to a certain size, it must periodically shed its outer cuticle the major part of the hard exoskeleton , and a new cuticle forms. Shedding of the old cuticle allows for increases in body size and other morphological changes.
The overall process may occur over days or even weeks without obvious outward signs because the new exoskeleton forms underneath the old one. Only when the old layer is actually being shed does it become apparent that the arthropod has been undergoing a molting phase.
Sequentially, the old cuticle now called an exuviae splits open, and the arthropod draws itself out. The new cuticle which consists of an outermost epicuticle layer, a middle exocuticle, and an inner endocuticle expands and hardens over several hours, primarily as the result of the cross-linking of proteins and chitin a polysaccharide derived from glucose in the exocuticle.
See also: Endocrine system invertebrate ; Insect physiology ; Metamorphosis. Animals might shed feathers, hair, skin, or an exoskeleton. An exoskeleton is a hard outer skeleton that protects an animal's body. Instead, these animals undergo multiple molts as they mature into adults.
All arthropods—including crustaceans, spiders, and insects—must regularly go through the molting process. But animals like snakes, birds, and dogs molt too. Humans have skin and bones that stretch and grow with us over time. But animals like the Dungeness crab in Washington have rigid outer bodies. All arthropods, including crustaceans, spiders, and insects, must regularly go through the molting process.
Molting not only lets crabs grow larger, but it also allows them to get rid of parasites and barnacles that might be living on their old shells. They can also regenerate lost legs! A typical crab molts between 30 and 40 times in its lifetime.
When a crab is ready to molt, it starts forming a soft paper-thin shell under its existing one. It also absorbs extra nutrients it will use later to harden its new shell.
The crab sucks in water to expand its body and split the old shell open. Then it starts wiggling out of the shell—a process that can take up to three hours. The crab fully exits its old shell. But it leaves behind its esophagus, stomach lining, and part of its intestine in the old shell. It must regrow these parts. The crab pumps more water into its body to increase its size. With a vulnerable soft shell, it will go into hiding until the shell hardens.
During its year-long life, a grasshopper develops from an egg to a nymph to an adult. Molting occurs five to six times, but only during the nymph stage. Unlike other arthropods, which molt throughout their entire lives, most insects—including grasshoppers—stop molting once they become adults. The insect then begins to grow a new exoskeleton inside its old one.
Once the new shell is ready, the insect gulps in as much air as possible and breaks out of its old shell. Then it quickly attaches its muscles and nerves to the new shell. Grasshoppers live only for a year. In that time, it develops from an egg to a nymph to an adult. It molts five to six times, but only during the nymph stage. Most arthropods molt throughout their entire lives.
But most insects, including grasshoppers, stop molting once they become adults. This chemical signal tells the grasshopper's body that's it's time to molt. In this state the insects are easy prey for predators. When snakes molt, they leave behind their old skin in one piece. Lillywhite from the University of Florida.
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