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Several litters and fast growing
young
The female carries the eggs on the underside
of her nether regions and mud shrimps are almost 1 mm long when they hatch.
They stay in their nursery until they have sloughed their exoskeleton
for the first time. After about 2 weeks they have developed enough to
leave their mothers burrow to dig their own. Mud shrimps can increase
in numbers very rapidly because they are able to have several litters
during the same summer, and the young from the first litter are able to
reproduce that same summer. Populations can in this way reach a density
of 70 000 individuals per m2.
Fishfood and aviation fuel
Because mud shrimps can
appear in such quantities they are an important source of
food for the common
shrimp, shore
crab, fish and birds.
Most mud shrimps live only one summer, but a
few individuals can hibernate during the winter and
thereafter build new populations the following summer.
There are several specie of mud shrimps
Corophium volutator has been the
most studied and probably the most noticable of the 6 sea-living specie
within the phylum that have been found in southern scandinavia. In addition
there are 3 freshwater specie known in the river systems of Finland
and those that merge into the southern Baltic and North Sea. These
specie are also found in brackish
water and it is very likely that at least some of these specie are
found in Swedish estural areas.
To distinguish between the different specie, the legs and
antennae need to be magnified and studied closely.
Bo Johannesson
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