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Distribution in scandinavian waters
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Maximum length: 0,6 cm. Compare
with the size of a hair.
Appearance: The water fleas body is covered by a two flapped
shell that creates an opening on the underside. The two quite complex
eyes have grown together. The second pair of antennae are large and
are used to swim. The head is large, and the rostrum is pointed and
powerful. There is also a point on the shells upper side. Compare the
water flea with the cladocerans
of the Evadne and the Podon
families.
Depth: From sea-level and a few metres deep.
Environment: Water fleas are mainly freshwater organisms, but
a few specie tolerate brackish
water. Because of this they are found in rock
pools close to the sea and in relatively closed seas with a large
run-off of freshwater, for example the northern reaches of the Baltic.
Misc: Water fleas eat small organisms and other particles in
the water. In turn they themselves are often eaten by larger creatures,
for example, fish. With some females the young water fleas develope
in the ovary without being fertilized.
Several generations with only females can occur and multiply themselves
partenogenetically. When harsher conditions prevail even males
and certain females whose eggs were fertilized hatch. The
ovaries are released when sloughing
takes place or when there is a drought and are spread over large areas
by the wind. Water fleas exist globally.
Classification: Water fleas are cladocerans, which are crustaceans
under the arthropods. Daphnia longispina is pictured above.
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