Q:
How do crabs breathe? How long can they stay
out of water?
A:
Crabs use their gills to extract oxygen from
the water, much like a fish. However, crabs can survive for long periods
out of water, and some live almost exclusively on land. As long as a crab
can keep its gills moist, oxygen from the air will diffuse into the
moisture, and then into the gills. One way to keep their gills from drying
out is to seek out cool, dark and moist hiding places when on land. This
way they can keep breathing and stay hidden from predators. Also, they
have articulating plates around their gills that help seal them in and
prevent drying out. Land crabs have even more adaptations to prevent
drying out. They drink water from dew and the ground, they get it from
food, and even from water vapor. They also store water in their bladder,
blood, and specialized pockets throughout their bodies.
This information obtained
from
OceanLink Answers to Anthropoda Questions
Q:
How do crabs find food in the dark?
A:
Crabs do not rely on vision like you and I
do, when looking for food. Crabs cannot see very well and usually only use
their vision when their prey is very close. Crabs find their food in the
dark (or in the light) by something called "chemoreception". This is kind
of like our sense of smell. They have very sensitive chemoreceptors (or
smell organs) on their antennae and in their mouthparts and distributed
throughout their body. So, crabs can "smell" the chemicals that their prey
put out in the water and follow these "smells" to find food.
This information obtained
from
OceanLink Answers to Anthropoda Questions
Q:
Do more crabs molt during a full moon?
A:
Some say yes and some say no.
Click here for more information.
Q:
Where do crabs go in the winter?
A:
When the water temperature starts to fall
and the days start getting shorter, the blue crab retreats to deep water
and burrows into the muddy or sandy bottom to spend the winter. A crab
buries itself by forcing its abdomen backwards into the bottom with quick
snapping motions. While doing this, the crab will also pick and claw at
the bottom with its hind walking legs and flip it away with the paddles of
its swimming legs. Within a few minutes the crab is resting at a 45° angle
in the bottom, with only antennae, the tips of its eye stalks, and small
breathing channels visible in the mud. Crabs do not hibernate, rather they
lie dormant for the long winter (usually from November through May.)
Q:
I've heard that a mouth bite from the blue
crab can cause death, is there any truth to this?
A:
The blue crab doesn't have a mouth (or
teeth) in which to bite, however people have been known to get blood
poisoning from a claw pinch if the the skin is broken (always wear
gloves!) As for a crab's mouth, located in the anterior portion of the
cephalothorax of the crab are its mouth parts, grouped around the opening
of the esophagus. These mouth parts are generally similar to those of
shrimps and lobsters. The outermost pair is the third maxillipeds, used
for holding food. Under and in front of these are two more pairs of
maxillipeds and two pairs of maxillae, also used for holding food, and a
pair of mandibles, or jaws, which push the food into the esophagus. |