Platyhelminths, also known as flatworms, are a diverse group of invertebrate organisms belonging to the phylum Platyhelminthes. They are characterized by their flattened, soft body structure, which gives them the distinguishable appearance of being flat. Platyhelminths are widely distributed across various terrestrial, marine, and freshwater habitats.
These organisms exhibit bilateral symmetry, meaning that their body can be divided into nearly identical halves along a central axis. Their body shape and internal organization vary based on their specific species. However, most platyhelminths lack a specialized respiratory or circulatory system, and many rely on diffusion to exchange gases and nutrients with their environment.
Platyhelminths encompass a wide range of species, including free-living flatworms as well as parasitic forms. Some free-living flatworms are found in marine or freshwater environments and play essential roles in aquatic ecosystems. On the other hand, certain parasitic platyhelminths are responsible for causing diseases in humans, livestock, and other animals.
The phylum Platyhelminthes is further divided into four classes: Turbellaria, Monogenea, Trematoda, and Cestoda. Turbellaria comprises non-parasitic flatworms, while Monogenea includes parasites that typically infest fish. Trematoda refers to flukes, which are parasites that have complex life cycles involving multiple hosts. Cestoda, also known as tapeworms, are long, segmented parasites that inhabit the intestines of their hosts.
Overall, platyhelminths represent a diverse group of organisms with varied ecological roles and significant impacts on both the natural world and human health.
