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Can holds its breath for a long
time
It is tough
sitting high up above the waterline. The Northern rock barnacle, that
often sits high up on the beach and unable to move, must find other ways
to survive hardships, e.g. heat, cold, variatians in salinity
and drought. The barnacle must also have the ability to breath in air,
but at the same time keep its shell closed to prevent evaporation and
dehydration, which is accomplished by occasionally by opening its shell
and changing air. If too much water evaporates, the salt content within
the barnacle can increase and have a negative effect. The cold also has
the same effect: when the water around the tissues freezes, salt content
will also increase in the unfrozen water.
Because of the barnacles protective calcareous
shell and tight skin, they are able to survive out of the
water at least a couple of weeks - even when it is warm and
dry during the summer. When conditions became critical, the
barnacle goes over to an anerobic way of life, meaning that
it can keep its shell closed tightly all the time and can
survive without oxygen.
It is not only high salt concentrations that cause problems
for the Northern rock barnacle, even brackish water effects the barnacle
negatively. Even then the barnacle closes its shell and goes over to an
anerobic life style when it rains at low
water.
Ice and the dogwhelk kill
The
dogwhelk can be quite common in certain areas, where it kills
and eats barnacles. To assault the barnacle, the dogwhelk
has to wait patiently until the barnacle has opened its shell.
At that time the dogwhelk inserts its rasp furnished trunk and scapes
up the softer parts of the barnacle. Occasionally, the dogwhelk
uses this trunk to bore a hole through the barnacles shell.
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