Quite often, periwinkles can survive large
injuries to their shells. In such cases the shell is repaired and a scar
is visible on the shell. Even if enemies cannot damage the shell, certain
creatures i.e. fish that are quick, can bite off the periwinkles foot
before it retracts it into the shell. Crabs sometimes manage to stick
in one of their claws into the shell aperture and pull out the soft parts,
which wading birds often do with the help of their long beaks.
It is quite common in some countries like France and Great
Britian that people
collect and eat periwinkles.
In its natural environment, the periwinkle is
seldom older than 3 years, but in an aquarium it is known
that an individual was as old as 20 years.
Worms in their shell
Quite often it is noticed that the spires
on large individuals are perforated with small holes that haved been bored
by a little polychaete. If the shell is submerged in the water it is possible
for the worm to stick out two long tentacles and catch microscopic particles
of food suspended in the surrounding water.
Females grow quicker and larger than males.
Reproduction takes place from the spring and until the middle of the summer.
During this period it is possible to see males trying to mate with both
males and females of their own species; and with other specie of periwinkle.
Successful mating entails that the male creeps up onto the right side
of the females shell and from that position place its long penis into
the shell aperture of the female. The female stores the sperm in a small
bladder and can fertilize several batches of eggs over a period of several
days after mating.
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