Crawdads, like all crustaceans, periodically shed their hard outer covering, known as an exoskeleton. This process, called molting or ecdysis, is necessary for these freshwater creatures to grow and maintain their health.
The Molting Process
The molting process begins with a preparatory phase called pre-molt. During this time, the crawdad’s body undergoes internal changes to prepare for shedding its rigid outer layer. Calcium is reabsorbed from the old exoskeleton and stored in specialized structures called gastroliths, which are disc-like calcium deposits found on either side of the stomach wall. This reabsorption weakens the old shell and provides minerals for the new one. If a crawdad has lost any limbs, regeneration of new limb buds begins during pre-molt, unfurling after the shed.
As the crawdad approaches the shedding phase, ecdysis, it absorbs water. This increases internal hydrostatic pressure, causing the body to swell and split the old exoskeleton. The old shell typically cracks along a line, often between the carapace (head region) and the abdomen (tail). The crawdad then backs out of its old shell, a process that can take hours or even several days. Immediately after emerging, the new exoskeleton is soft and pliable, allowing the crawdad to expand its size.
Why Crawdads Shed Their Shell
Crawdads shed their shells primarily for growth. Their hard exoskeleton does not expand, so as the crawdad grows, it becomes constrained. Molting allows the crawdad to increase in size. Young crawdads molt more frequently, sometimes every 7 to 10 days, due to rapid growth. Older individuals molt less often, potentially every 30 to 40 days or more.
Beyond growth, molting also serves other biological functions. It allows the crawdad to repair damage to its exoskeleton. The shedding process also helps in the removal of parasites or other attached organisms from the old shell. This ensures the crawdad maintains a healthy outer defense.
Life After the Shed
Following the successful shedding of its old shell, the crawdad enters a highly vulnerable period. Its newly exposed exoskeleton is extremely soft and offers little protection against predators or other environmental threats. During this time, crawdads instinctively seek out hiding places, such as crevices, burrows, or dense vegetation, to remain concealed until their new shell hardens.
The crawdad uses the calcium it reabsorbed and stored in its gastroliths during the pre-molt stage to quickly begin calcifying its new shell. In some cases, crawdads may also consume their discarded exoskeleton, known as the exuvia, to reclaim additional valuable nutrients like calcium and phosphorus. This consumption aids in the rapid hardening of the new shell, a process that can take several days to complete. Once the new shell has fully hardened, the crawdad can resume its normal activities with a larger, fully protective exoskeleton.