Turbellaria

File:Bedford's Flatworm.jpg

Bedford's Flatworm

Pseudoceros dimidiatus

Mating Pseudobiceros bedfordi

Turbellaria is a class of mostly free-living flatworms belonging to the phylum Platyhelminthes. These organisms are primarily aquatic, inhabiting both marine and freshwater environments, although some species are terrestrial. Turbellarians are known for their ciliated epidermis, which aids in locomotion.

Characteristics

Turbellarians are characterized by their soft, flattened bodies and a lack of specialized respiratory and circulatory systems. They rely on diffusion for gas exchange and nutrient distribution. The body is covered with cilia, which are used for movement and feeding. Turbellarians exhibit a range of body sizes, from a few millimeters to several centimeters in length.

The digestive system of turbellarians is simple, often consisting of a mouth, pharynx, and a branched gut. Some species have a protrusible pharynx that can be extended to capture prey. Turbellarians are mostly carnivorous, feeding on small invertebrates and organic debris.

Reproduction

Turbellarians can reproduce both sexually and asexually. Sexual reproduction involves the exchange of sperm between individuals, as most turbellarians are hermaphroditic, possessing both male and female reproductive organs. Asexual reproduction occurs through fission, where the organism splits into two or more parts, each of which regenerates into a complete individual.

Ecology

Turbellarians play a significant role in aquatic ecosystems as predators of small invertebrates and as prey for larger animals. They are important in the food web, contributing to the control of invertebrate populations and the recycling of nutrients.

Classification

Turbellaria is traditionally divided into several orders, including Tricladida, Polycladida, and Rhabdocoela. However, recent molecular studies have suggested that Turbellaria is not a monophyletic group, leading to revisions in their classification.

Related pages

• Platyhelminthes
• Flatworm
• Cilia

References

• Ruppert, E. E., Fox, R. S., & Barnes, R. D. (2004). Invertebrate Zoology. Brooks/Cole.
• Tyler, S., Schilling, S., Hooge, M., & Bush, L. F. (2006). "Turbellarian taxonomic database". Version 1.4. Available at: [1]