Didinium
Didinium is a genus of predatory ciliates belonging to the order Haptorida. They are characterized by their barrel-shaped bodies and the presence of a prominent proboscis or cytostome, which is used to capture and engulf their prey. Didinium primarily feed on other ciliates, particularly Paramecium.
Characteristics:
- Shape: Typically barrel-shaped or globular.
- Size: Microscopic, generally ranging from 50 to 200 micrometers in length.
- Proboscis: A retractable proboscis or cytostome is the most distinctive feature. It is located at the anterior end and used for capturing and ingesting prey.
- Cilia: Possess bands of cilia arranged around the body, though these may be reduced compared to other ciliates.
- Macronucleus: Contains a single, large macronucleus that is responsible for vegetative cell functions.
- Contractile Vacuole: A contractile vacuole helps regulate osmotic pressure.
Ecology:
Didinium are found in freshwater habitats, including ponds, lakes, and streams. They play an important role in the microbial food web as predators, controlling populations of other ciliates, especially Paramecium. Their presence and population dynamics can influence the structure and stability of microbial communities. When a Didinium population is introduced to a Paramecium population, oscillations between the two populations usually occur - the Didinium population will increase with available Paramecium, however, once the Paramecium are consumed, the Didinium population will rapidly decline.
Reproduction:
Didinium reproduce asexually through binary fission. During fission, the cell divides into two identical daughter cells. Sexual reproduction, through conjugation, has also been observed.
Classification:
- Kingdom: Protista
- Phylum: Ciliophora
- Class: Litostomatea
- Order: Haptorida
- Family: Didiniidae
- Genus: Didinium