Lobsters undergo molting, also known as ecdysis, to grow and survive. Because a lobster’s shell, or exoskeleton, cannot expand, molting is the only way for the animal to increase in size. This process allows them to grow larger and replace damaged or worn-out shells.
The Shedding Process
The molting process begins with hormonal changes that soften the lobster’s existing exoskeleton, particularly between the abdomen and tail. A new, soft shell then forms underneath the old one, an exact replica of the lobster’s body. Minerals, including calcium, are reabsorbed from the old shell and stored in the lobster’s body, in structures called gastroliths near the stomach, to be used for hardening the new shell.
As the lobster prepares to shed, it absorbs excess water, increasing internal pressure against the old shell, which causes the shell to split, typically along the seam between the carapace (main body section) and the tail. The lobster then rolls onto its side and bends almost in half, slowly pulling itself out of its old exoskeleton, including its stomach lining and rigid parts of its digestive system. The discarded outer shell is called the exuvia. Emerging from the old shell can take as little as 8-10 minutes, though the overall molting event, including preparation, can last for several hours.
Life Beyond the Old Shell
Immediately after shedding, the lobster’s new shell is extremely soft and flexible, resembling paper or even jelly. During this vulnerable period, known as the soft-shell phase, the lobster rapidly absorbs seawater to expand its body. This ensures the new shell hardens into a larger size, allowing for future tissue growth within the new exoskeleton. This water absorption can increase the lobster’s body weight by approximately 10%.
The new shell begins to harden almost immediately, though it can take anywhere from a few days to several weeks to become fully rigid. The stored calcium from the old shell is redeposited into the new one, accelerating the calcification process. Lobsters often consume their own shed shells to expedite hardening and replenish lost nutrients, recycling valuable calcium. During this time, soft-shelled lobsters are susceptible to predators and infections due to their lack of protective armor. They often seek hiding places in rocks or crevices until their new shell is strong enough for protection.
Molting Frequency and Purpose
Molting is a continuous process throughout a lobster’s life, with its frequency decreasing as the lobster ages and grows larger. Young lobsters, growing rapidly, may molt frequently, sometimes every few weeks or months. For example, a lobster might molt up to 25 times within its first five to seven years of life. This frequent shedding allows them to increase their size significantly, with each molt resulting in about a 20% increase in size.
As lobsters mature, molting becomes less frequent. Adult males typically molt about once a year, while adult females may molt once every one to two years. The primary purpose of molting is growth. Beyond growth, molting also allows lobsters to regenerate lost limbs or antennae, repair damaged shells, and facilitate the development of reproductive structures. Factors like water temperature and food availability can influence the timing and frequency of molting.