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Planariam (family Planariidae) are common freshwater, non-parasitic flatworms of the phylum Platyhelminthes, class Turbellaria. It should be noted that the term "planaria" is most often used as a common name. It is also the name of a genus within the family Planariidae. It moves by beating cilia on the ventral dermis, allowing it to glide along on a film of mucus. Some move by undulations of the whole body by the contractions of muscles built into the body wall. They exhibit an extraordinary ability to regenerate lost body parts. For example, a Planaria split length wise or crosswise will regenerate into 2 separate individuals. The size ranges from 3 to 12 mm, and the body has two eye-spots (also known as ocelli) that can detect the intensity of light. The eye-spots act as photoreceptors and are used to move away from light sources. Planaria have 3 germ layers (ectoderm, mesoderm, and endoderm), but are acoelomate (having a solid body with no coelom, or body cavity). Thei have a single-opening digestive tract, consisting of one anterior branch and two posterior branches in freshwater planarians. Because of this three-branched organization, freshwater flatworms are often referred to as triclad planarians. They are active carnivious flatworms that feed on daphnie and midge and skipper. Image File history File linksMetadata Download high resolution version (2116x880, 439 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...
Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ...
“Animalia†redirects here. ...
subgroups Ctenophora Cnidaria Bilateria Eumetazoa is a clade comprising all major animal groups except sponges. ...
The Platyzoa are a group of protostome animals. ...
Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ...
Orders Acoela Catenulida Haplopharyngida Lecithoepitheliata Macrostomida Nemertodermata Polycladida Prolecithophora Rhabdocoela Seriata Turbellaria are a group of generally small (<1 - 60cm) and free-swimming members of the flatworm phylum Platyhelminthes. ...
For the village on the Isle of Wight, see Freshwater, Isle of Wight. ...
Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ...
Orders Acoela Catenulida Haplopharyngida Lecithoepitheliata Macrostomida Nemertodermata Polycladida Prolecithophora Rhabdocoela Seriata Turbellaria are a group of generally small (<1 - 60cm) and free-swimming members of the flatworm phylum Platyhelminthes. ...
cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ...
In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...
The dermis is a layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. ...
Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ...
In biology, regeneration is an organisms ability to replace body parts. ...
Photoreceptors are light-sensitive proteins involved in the function of photoreceptor cells. ...
Organs derived from each germ layer. ...
[image:FlatwormZIKA.pog|thumb|right|Side View]
Planaria are common to many parts of the world and reside in fresh water ponds and rivers. They are also commonly found residing on plants.
The most frequently used in the high school and first-year college laboratories is the brownish Dugesia tigrina. Other common varieties are the blackish Planaria maculata and Dugesia dorotocephala. Recently, however, the species Schmidtea mediterranea has emerged as the species of choice for modern molecular biological and genomic research due to its diploid chromosomes and existence in both asexual and sexual strains. Recent genetic screens utilizing double-stranded RNA technology have uncovered 240 genes that afect regeneration in S. mediterranea. Interestingly, many of these genes are found in the human genome (see link below).
Anatomy and physicology
 Planarian on the glass of an aquarium. The planarian has very simple organ systems. The digestive system consists of a mouth, pharynx, and an intestine. The mouth is located in the center of the underside of the body. Digestive enzymes secrete from mouth to begin external digestion. The pharynx connects the mouth to the intestines. The intestines of the Planaria branch throughout the body. They eat living or dead small animals that they suck with their muscular mouth. From there, the food passes through the pharynx into the intestines and digesting of the food takes place in the cells lining the intestine, which then diffuses to the rest of the body. Image File history File linksMetadata Flatworm. ...
Image File history File linksMetadata Flatworm. ...
It has been suggested that this article or section be merged with mouth (human). ...
The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. ...
In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine (or colon). ...
Planare receive oxygen and release carbon dioxide by diffusion. The excretory system is made of many tubes with many flame cells and excretory pores on them. Flame cells remove unwanted liquids from the body by passing them through ducts that lead to excretory pores where the waste is released on the dorsal surface of the planarian. At the head of the planarian there is a brain under the eyespots. From the brain there are two nerve cords which connect at the tail. There are many transverse nerves connected to the nerve cords which make it look like a ladder. With a ladder-like nerve system it is able to respond in a coordinated manner. This article or section does not cite any references or sources. ...
A flame cell is a specialized excretory cell found in the Platyhelminthes (except the tubellarian order Acoela), these are the simplest animals to have a dedicated excretory system. ...
In animals the brain, or encephalon (Greek for in the head), is the control center of the central nervous system, responsible for thought. ...
Nerves (yellow) Nerves redirects here. ...
Reproduction A planarian can reproduce either asexually or sexually. In asexual reproduction the planarian detaches its tail end and each half regrows the lost parts. In sexual reproduction each Planaria gives and receives sperm. Planaria have both testes and ovaries. Eggs develop inside the body and are shed in capsules. Weeks later the eggs hatch anb grow into adults. Planarians can also reproduce by regeneration. If a Planaria is cut into two halvel, both halves may become two new Planaria (regeneration). In one experiment, T.H. Morgan found that a peace coresponding to (wusup homie G dog, Home Skillet- Biskit⁄279th of a planarian could successfully regenerate into a new worm. This size (about 10,000 cells) is typically accepted as the smallest fragment that could regrow into a new planariam. It has been suggested that Parthenogenesis be merged into this article or section. ...
Sexual reproduction is a union that results in increasing genetic diversity of the offspring. ...
In biology, regeneration is an organisms ability to replace body parts. ...
Thomas Hunt Morgan in 1891. ...
See also Memory RNA is a now-discredited hypothetical form of RNA that was proposed by James V. McConnell and others as a means of explaining how long-term memories were stored in the brain. ...
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