Vorticella

Description:

Vorticella is a unicellular ciliated aquatic protist. Newly budded cells are free swimming, but in older organisms, the long stalk is usually attached to some sort of substrate such a plant detritus, rocks, or even animals such as crustaceans. During most of the life cycle, the cilia are localized to the “mouth” of the cell (peristome). These cilia sweep bacteria into the peristome where they are ingested by phagocytosis. The stalk of cell has several layers, including a contractile structure called a spasmoneme or myoneme (the thin, helical structure seen within the stalk in some photos). The spasmoneme allows the stalk to contract in a coiling pattern. This contraction happens so quickly that Vorticella is considered the fastest moving organism known. Contraction and the much slower relaxation of the stalk occurs in response to environmental disturbances and may be used in feeding as well. The bell-shaped “head” of the cell contains most of the organelles, including two nuclei (an S- or C-shaped macronucleus and a round micronucleus) and a contractile vacuole that prevents osmosis from destroying the cell. Vorticella can reproduce both sexually and asexually. They may be found individually or in large groups. Identification of species based on morphology is difficult at best, and unambiguous identification typically requires DNA sequence analysis (specifically, the sequence small subunit ribosomal RNA genes).

Habitat:

Vorticella is strictly aquatic, typically found in freshwater environments. This specimen was collected from a small vernal pool.

Notes:

The components and mechanism of spasmoneme movement involves calcium-binding proteins, including centrin (a component of basal bodies and involved in the movement of flagella and cilia) and spasmin. The spasmoneme is being studied in the context of nanotechnology applications. The video clip shows that, in addition to the movement of cilia, shape changes is the peristome occur during feeding. You can also get an idea of the speed of contraction as the organism periodically disappears from view. Another video of the whole organism can be seen here: https://vimeo.com/66332939. You can see the whole organism contracting, and what happens when a big rotifer runs into it.