Description of Vorticella
(
anglais
)
fourni par BioPedia
As with the majority of peritrich ciliates, Vorticella has a bell-shaped body and attached to the substrate by means of a stalk. The stalk is contractile, there is an inner element called the spasmoneme that can contract very rapidly. Contractile elements also extend into the body of the cell so the body rounds up when the cell contracts. Normally, there is a wreath of feeding cilia at the unattached end of the cell, and these create a water current from which small particles of food (mostly bacteria) can be removed and ingested. Vorticella cells usually reproduce by forming a daughter cell that has a basal wreath of cilia. This cell breaks away from the parent, and swims around as a cylindrical telotroch larva. Eventually it settles, attached by the back end, withdraws the basal wreath of cilia, secretes the stalk and changes into a more conical shape. Occasionally, when conditions are not satisfactory, cells may sprout a basal wreath of cilia, break away from their stalk, and swim around settling at another location. This is a solitary species, in that the cells do not form colonies, although it is not unusual to find many individual Vorticella cells living side-by-side and to form a cluster. The behavior of contracting is quite distinctive and because of this, we know that this is one of the first free-living protozoa to be described (by Antony van Leeuwenhoek in the 17th century).
