Suctoria are peculiar ciliates which are sessile, feed by extracellular digestion and lack cilia in the adult phase. They are found in both freshwater and marine environments, including some which live on the surface of aquatic animals, and typically feed on other ciliates. Instead of a single cytostome, each cell feeds by means of several specialized tentacles. These are supported by microtubules and phyllae, and have toxic extrusomes called haptocysts at the tip which attach to prey. Its cytoplasm is then sucked directly into a food vacuole inside the cell, where its contents are digested and absorbed. Most suctoria are around 15-30 μm in size, with a non-contractile stalk and often a lorica or shell. Classes & Subclasses Class Karyorelictea Class Heterotrichea (e. ... A cytostome or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. ... Extrusomes are membrane-bound structures in some eukaryotes which, under certain conditions, discharge their contents outside the cell. ... Vacuoles are large membrane-bound compartments within some eukaryotic cells where they serve a variety of different functions: capturing food materials or unwanted structural debris surrounding the cell, sequestering materials that might be toxic to the cell, maintaining fluid balance (called turgor) within the cell, exporting unwanted substances from the...

Suctoria reproduce primarily by budding, producing swarmers which lack both tentacles and stalks but have cilia. They may also reproduce through conjugation, which is peculiar in involving cells of different size and often involves total fusion. The way in which buds are formed is the primary way the different orders of suctoria are distinguished. Among the Exogenida, including common genera like Podophrya and Sphaerophrya, they appear directly on the cell surface. Among the Endogenida, for instance Tokophrya and Acineta, they are formed in an internal pouch and escape through an opening, and among the Evaginogenida, they are formed in a pouch that inverts before they are released.

Once the swarmers have found a place to attach themselves, they quickly develop stalks and tentacles. The cilia are lost, but the underlying infraciliature persists throughout the entire life-cycle. This has a structure which, together with other ultrastructural similarities, places the suctoria within the class Phyllopharyngea. Typical orders Subclass Phyllopharyngia     Chlamydodontida     Dysteriida Subclass Chonotrichia     Exogemmida     Cryptogemmida Subclass Rhynchodia     Rhynchodida     Hypocomatida Subclass Suctoria     Exogenida     Endogenida     Evaginogenida The Phyllopharyngea are a class of ciliate protozoa, including some which are extremely specialized. ...

Below is link to good page showing video's and pictures of some suctorians: http://www.microscopy-uk.org.uk/mag/artmar03/jmcsuctoria.html