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Protozoa: Ciliates
The Peritrich Ciliates. 
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Protozoa: Home Ciliates: Home Holotrich Heterotrich Peritrich Colonial Suctoria

  Peritrich Ciliates.

Peritrichs are ciliates which have no body ciliature other than that fringing the mouth end of the organism and which creates the current bringing food particles to the mouth (buccal cavity).
They are rarely free-swimming, usually sessile, sometimes enclosed in a vase-shaped lorica, but most frequently as separate stalked organisms and as branched colonies of up to a hundred or more individuals. (See Colonial Ciliates, most of which are peritrichs).


Vorticella, the classic peritrich, was also called the "bell animalcule" by early microscopists on account of its shape when fully extended (see diagram).
It is one of the more common microscopic creatures in fresh water. It is sessile, and can be found attatched to practically anything including small crustaceans such as water fleas, but more commonly on submerged plants and rocks. It is attatched by a contractile stalk -- a tubular structure with a central muscle fibre (myoneme) which very rapidly pulls the stalk into a tight spiral when the organism is disturbed. It slowly extends again when the disturbance has passed.
This contraction holds the record for the fastest known action in the Animal kingdom.

When conditions become adverse, the Vorticella can develop cilia around its base and detatch itself from its stalk to swim freely in search of a more congenial environment; whereupon it attatches again and generates another stalk. The free-swimming organism is called a telotroch, and in this form can be difficult to recognize as a Vorticella.
There are also green varieties of Vorticella (see below) which establish a symbiotoic relationship with unicellular algae (zoochlorellae).

All varieties feed mostly upon suspended bacteria, but also consume algal unicells and smaller protozoa.

Vorticella. A group of Vorticella actively feeding on organic debris amongst filamentous bacteria. Vorticellae often occur in groups, but these groups are not strictly speaking colonies as there is no connection between the individual organisms -- they are each attatched to the substrate by their own separate contractile stalk.
Darkfield: x100.
Vorticella. A single Vorticella actively feeding. Seen in profile, two of the three rows of cilia are visible, forming a counterclockwise spiral around the perimeter of the bell shape, and ending in the buccal cavity. Several small food vacuoles can also be seen.
Here is a diagram showing details of the ciliature.
Brightfield: x1000.
Vorticella. Another single Vorticella feeding. Phase contrast illumination clearly shows the muscle fibre (myoneme) which runs the length of the contractile stalk. The two free-swimming organisms immediately beneath are a flagellate, and (at bottom) the euglenoid Phacus.
Phase Contrast: x400.
Vorticella. A single Vorticella attatched to a filament of the alga Cladophora which is heavily encrusted with diatoms and other epiphytes. Its stalk is practically invisible in this picture.
Darkfield: x200.
Vorticella. Vorticella feeding. The bright organism in the background makes it easier to see the stalk with its central myoneme.
Darkfield: x400.
Vorticella. A Vorticella in sewage sludge. The long vaguely horseshoe-shaped nucleus can be seen.
Darkfield: x500.
Vorticella dividing. The final stages of cell division in Vorticella. The lower cell is the daughter, which will separate from the parent and swim away, assisted by both the normal adoral cilia as well as a skirt of cilia which can only just be seen circling the body nearest the point of attatchment. The daughter will find a place to attatch itself and generate a stalk of its own.
Darkfield: x400.
Vorticella dividing. A swarm of green Vorticellae, densely packed with commensal algae (zoochlorellae). When the pondwater containing them was first prepared as a microscope specimen, they were all attatched by their stalks and feeding vigourously. In the time it took to prepare the camera for the shot, they had almost all detatched themselves from their stalks, presumably because their new living conditions were no longer to their liking. In this free-swimmimg state, they are described as telotrochs.
Darkfield: x150.

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