The flatworms, flat worms, Platyhelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates, and have no specialised circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion and egestion ; as a result, the food cannot be processed continuously.
Gnathostomulids, or jaw worms, are a small phylum of nearly microscopic marine animals. They inhabit sand and mud beneath shallow coastal waters and can survive in relatively anoxic environments. They were first recognised and described in 1956.
The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from 1 mm (0.039 in) to large freshwater forms more than 500 mm (20 in) long or terrestrial species like Bipalium kewense which can reach 600 mm (24 in) in length. All the larger forms are flat with ribbon-like or leaf-like shapes, since their lack of respiratory and circulatory systems means that they have to rely on diffusion for internal transport of metabolites. However, many of the smaller forms are round in cross section. Most are predators, and all live in water or in moist terrestrial environments. Most forms reproduce sexually and with few exceptions all are simultaneous hermaphrodites.
Acoelomorpha is a subphylum of very simple and small soft-bodied animals with planula-like features which live in marine or brackish waters. They usually live between grains of sediment, swimming as plankton, or crawling on other organisms, such as algae and corals. With the exception of two acoel freshwater species, all known Acoelomorphs are marine.
The Polycladida represents a highly diverse clade of free-living marine flatworms. They are known from the littoral to the sublittoral zone, and many species are common from coral reefs. Only a few species are found in freshwater habitats.
Pseudocerotidae is a family of flatworms which includes the Bedford's flatworm. Pseudocerotidae are simple organisms categorized by their oval bodies and tentacles and bright colors. They use the cilia to glide along surfaces. Most commonly referred to as marine flatworms, closely related to the orders Macrostomorpha and Lecithoepitheliata. These organisms have very complex reproductive systems, no blood systems or organs for gas exchange, a simple brain and are hermaphroditic.
Pseudoceros is a genus of the flatworms Platyhelminthes.
Geoplanidae is a family of flatworms known commonly as land planarians or land flatworms.
Pseudobiceros is a genus of flatworms. Like all flatworms, Pseudobiceros are hermaphrodites. This particular genus engages in penis fencing. When the "winner" touches its penis to the "skin" of the other, insemination occurs, and the "loser" has to bear the burden of motherhood.
Pseudoceros bicolor, known as the two-colored flatworm, is a rare species of polycladid flatworm.
The Lecithoepitheliata are an order of rhabditophoran flatworms. They are free-living worms, found in freshwater, soil, and marine environments. However, it is still poorly known their roles in the natural food web.
Pseudoceros ferrugineus, the Fuchsia flatworm, is a marine flatworm species that belongs to the Pseudocerotidae family.
Pseudoceros lindae, common name Linda's flatworm, is a marine Flatworm species that belongs to the Pseudocerotidae family.
Thysanozoon nigropapillosum is a species of polyclad flatworms belonging to the family Pseudocerotidae. Some common names include gold-speckled flatworm, marine flatworm, yellow papillae flatworm, yellow-spotted flatworm, and yellow-spotted polyclad flatworm.
Pseudoceros susanae is a marine flatworm species that belongs to the Pseudocerotidae family.
Cotylea is a suborder of free-living marine turbellarian flatworms in the order Polycladida.
Müller's larva or Mulleria is a larva of some Polycladida. It has 8-fold symmetry and is somewhat like a ctenophore. Müller’s larva is ciliated and has several paired and unpaired lobes. The cilia on the lobes are longer than cilia on the rest of the body. At the anterior and posterior ends of the larva are tufts of longer cilia. The apical tuft originates from the apical organ, a sensory structure associated with the central nervous system.
Diana Marcela Bolaños Rodríguez is a Colombian marine biologist who has studied and classified various types of platyhelminths. She was a recipient of the L'Oréal-UNESCO Fellowship for Women in Science in 2010, was selected as Colombian biologist of the year in 2012, and in 2013 was named by the BBC as one of the top ten women in science in Latin America.
Trepaxonemata is a subclass of the Platyhelminthes or flatworms. It includes all parasitic flatworms and several free-living species that were previously grouped in the now obsolete class Turbellaria. Therefore, it contains the majority of species in the phylum Platyhelminthes, excluding the Catenulida, and the Macrostomorpha.
Pseudoceros canadensis, commonly known as the Puget flatworm, is a species of free-living flatworm in the genus Pseudoceros, belonging to the family Pseudocerotidae.
