An exoskeleton is a hard layer outside some creatures’ bodies. An exoskeleton is an ‘external skeleton,’ the opposite of an endoskeleton.
But invertebrate insects aren’t the only creatures with exoskeletons. Spiders, centipedes, crabs, snails, and lobsters all have a kind of external armor.
Some creatures can outgrow their exoskeletons – a rigid exoskeleton can prevent development, so some animals will shed their armor and grow it again. This process is called ecdysis, or ‘molting.’ After that, there’s a period when the new exoskeleton is soft and has to harden over time.
Creatures that outgrow their exoskeletons include:
- Hermit crabs
Except for hermit crabs, creatures with shells do not generally outgrow and shed their exoskeletons. Instead, their bodies expand as they do.
Animals with expanding shells include: