In general, the crab's
mating period usually comes after a short period
of courtship, in
which a male searches for a female about to molt her
shell. He
then cradle-carries her beneath him for two to three days until she
sheds her shell
and her new one hardens. At this point, the mating process
begins, which normally
lasts five to twelve hours. After the eggs are
fertilized, they
remain on the outside of the female's body until the
larvae emerge.
Very few species emerge from the egg looking like miniature
crabs. These
"zoea" larvae go through a series of body molts in order to reach
a stage called the
"megalops" larvae, in which they finally resemble a
crab. After
many more developments, the larva develops into a mature, adult crab.
Many of the eggs
are killed by fungi, eaten by worms, suffocate in low-oxygen
water or die in
too high or low water temperatures. Jellyfish, fish and other
enemies eat many
of the zoea and megalops larvae. Only a lucky 0.0001 percent
of the eggs become
full-fledged adults in as little as one year after hatching.
These various factors
affect where crabs lay their eggs depending on
favorable conditions.
Different species
of crabs have different reproduction processes. As
in the Alaskan King
Crab, the female lays her eggs and then sometime later
they are fertilized
by the male externally. The Land Hermit Crabs have genital pores
located on their
pereiopod and the males specifically have a coxal tube as an
extension of a pereiopod.
Their reproduction occurs when their shells are hard
and are often in
or near the burrows of the males. The male places a
spermatophore on
the female, which is dissolved by secretions as the eggs
are released.
The eggs are attached to the female's abdomen and stay
there until she
leaves them on the wet sand or rock for the tide to carry
them out to sea
and they hatch. The Blue Crabs mate primarily in low salinity
waters selected
by female crabs for molting. After carrying the female for a
few days, he stays
with her during the process. Unlike Blue Crab males,
the females only
mate once. The male's spermatozoa are stored in the
female for later
fertilization, so that the female uses this for repeated
spawnings.
The eggs (The spongy orange stuff in the picture) are stored on the abdominal
of the Blue Crab female for up to two weeks.
