Changes

Before moulting, the lobster’s skin cells enlarge and secrete the beginning of a new shell under the old one, and calcium accumulates in reservoirs called [[gastrolith]]s on either side of the stomach. During moulting, the lobster pumps sea water into its shell and distributes it around its body so that [[hydrostatic pressure]] forces the old shell away from the new one.  

Before moulting, the lobster’s skin cells enlarge and secrete the beginning of a new shell under the old one, and calcium accumulates in reservoirs called [[gastrolith]]s on either side of the stomach. During moulting, the lobster pumps sea water into its shell and distributes it around its body so that [[hydrostatic pressure]] forces the old shell away from the new one.  

When the lining membrane bursts, the lobster is helpless for twenty minutes, and then must detach itself from its old shell. This is easier said than done. It must lose the mass of muscle in its great claws, or it cannot pull them through the shell around its wrists. Because the teeth inside its stomach that grind its food are part of the exoskeleton, the lobster must pull out the lining of its [[throat]], [[stomach]] and [[anus]] before it can be free of the old shell. Not all lobsters survive moulting.  

When the lining membrane bursts, the lobster is helpless for twenty minutes, and then must detach itself from its old shell. This is easier said than done. It must lose the mass of muscle in its great claws, or it cannot pull them through the shell around its wrists. Because the teeth inside its stomach that grind its food are part of the exoskeleton, the lobster must pull out the lining of its [[throat]], [[stomach]] and anus before it can be free of the old shell. Not all lobsters survive moulting.  

After this stage, the lobster digests its gastroliths in order to recycle some of the calcium from its old shell into the new one. This calcium goes to harden the tips of the legs and the cutting edges of the mouthparts, without which the lobster cannot feed. It pumps itself full of water again, to expand to a larger size than that contained by the old shell, and then eats its old shell as another source of calcium.

After this stage, the lobster digests its gastroliths in order to recycle some of the calcium from its old shell into the new one. This calcium goes to harden the tips of the legs and the cutting edges of the mouthparts, without which the lobster cannot feed. It pumps itself full of water again, to expand to a larger size than that contained by the old shell, and then eats its old shell as another source of calcium.