|
How do crabs grow?
The rigid shell imprisons the
crab and limits growth.
Crabs grow by
shedding their outgrown shell.
Once the shell is shed, the crab can absorb
water and expand into its new-grown shell.
|
 |
Having reached the "buster" molt
stage, a Maryland blue crab, Callinectes sapidus, sheds its
shell. During its lifetime a crab may molt 20 to 25 times,
increasing its size as much as 1/4 to 1/3 each time. |
|
Photos
Courtesy of Mary
Hollinger, NODC biologist, NOAA
- America's Coastlines Collection |
|
 |
 |
How much does a blue crab
increase in size on molting?
Under normal conditions, the Blue Crab increases about one-third
it's size with each molt.
 What is the difference
between soft and hard shell crabs?
They are the same species.
A soft-shell crab is a crab that has just discarded its shell.
Immediately after the molt, when the old hard shell has been shed,
the crab's new shell is pliable and easily stretched. Now the crab is
called a "soft crab" or a "soft shell crab".
Large amounts of water are consumed prior to and shortly after the
molt, causing the soft shell to expand and increase in size. This entire
process takes 2-3 hours and within 2 hours after the shed, the new shell
begins to harden.
Crabs which have just shed their shell hide in rocks or bury
themselves in sand and mud to escape predators.
The "papershell" is formed within 12 hours and an additional 2-3 days
are needed before the shell fully hardens.
They come back out after the new shell hardens.
|
