Geographic Range |
Mediterranean, Black Sea, Eastern Atlantic. |
Physical Characteristics |
it is sessile, it has an oval operculum and
a scarious base which sticks to the substratum. The shell is made up of
six limestone plates of similar dimension; the upper opening (operculum)
can close in order to protect the animal in case of long periods out of
the water and of increase in the salinity. The shell diameter may be up
to 14 millimeters wide, but its dimension depends on the habitat, on the
quantity of available food and on the tide level. The tissue inside the
operculum is light blue with brown and orange spots. |
Notes |
it feeds thanks to the movement of the cirri,
which go out of the operculum to catch the plankton and the organic material
suspended in the water. They change their moult several times to grow up.
The feeding rate and the temperature determine the frequency of the moult.
No moult takes place during wintertime when the levels of phytoplankton
and the temperature are low. All these species grow faster during their
youth and less fast afterwards; their generally conical shell tends to become
tubular when the species grows in areas with a high density of individuals.
The rate of growth changes according to different biological and environmental
factors, such as the flow of the current, the orientation with regard to
the current, the food availability, the exposure to the waves, the level
of the tide, the intra- and inter specific competition. The reproduction
is autogamous and that means that the female gamete is inseminated by the
male gamete produced by the same individual. It reproduces every year. It
is sensitive to the decrease in the salinity and to the increase in the
sediment load. |
Habitat |
it is found in the middle and low eulittoral
zone on the exposed rocky coasts. |