Crossword clues for planarian
The Collaborative International Dictionary
Planarian \Pla*na"ri*an\, n. (Zo["o]l.) One of the Planarida, or Dendroc[oe]la; any turbellarian worm. -- Pla*na"ri*an, a.
Wiktionary
n. Any of various flatworms of the order ''(taxlink Tricladida order noshow=1)'' living in marine, freshwater, or terrestrial environments.
WordNet
n. free-swimming mostly freshwater flatworms; popular in laboratory studies for the ability to regenerate lost parts [syn: planaria]
Wikipedia
A planarian is one of many flatworms of the Turbellaria class. It is also the common name for a member of the genus Planaria within the family Planariidae. Sometimes it also refers to the genus Dugesia.
Planaria are common to many parts of the world, living in both saltwater and freshwater ponds and rivers. Some species are terrestrial and are found under logs, in or on the soil, and on plants in humid areas.
Planaria exhibit an extraordinary ability to regenerate lost body parts. For example, a planarian split lengthwise or crosswise will regenerate into two separate individuals. Some planarian species have two eye-spots (also known as ocelli) that can detect the intensity of light, while others have several eye-spots. The eye-spots act as photoreceptors and are used to move away from light sources. Planaria have three germ layers ( ectoderm, mesoderm, and endoderm), and are acoelomate (they have a very solid body with no body cavity). They have a single-opening digestive tract; in Tricladida planarians this consists of one anterior branch and two posterior branches.
Planarians move by beating cilia on the ventral dermis, allowing them to glide along on a film of mucus. Some also may move by undulations of the whole body by the contractions of muscles built into the body membrane.
Triclads play an important role in watercourse ecosystems and are often very important as bio-indicators.
The most frequently used planarian in high school and first-year college laboratories is the brownish Girardia tigrina. Other common species used are the blackish Planaria maculata and Girardia 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 the existence of both asexual and sexual strains. Recent genetic screens utilizing double-stranded RNA technology have uncovered 240 genes that affect regeneration in S. mediterranea. Many of these genes have orthologs in the human genome.
Usage examples of "planarian".
Touch a planarian firmly with a glass rod and it will curl itself into a ball - its normal response to a threatening situation.
Your assistants, hereinafter to be called students, have been selected for planarian accelerated education.
Edgar sipped his drink and grimly contemplated the entire planarian idea.
When these trained worms were ground up and fed to other planarian worms, these latter learned the same responses faster than worms not so fed.
A small, hairless, closed-eye cross between a planarian and Khrushchev, ID tag illegible.
Robert Jordan and James McConnell, while still graduate students, began doing experiments with planarian worms at the University of Texas, studies that McConnell continued while a professor at the University of Michigan.
They assembled and reared into a single mass, cobra-like, but flat as a planarian worm.
Both ends of the planarian worm elongate, and soon there are two worms, two identities, two digestive systems, each as greedy as the original, each a whole, unwounded, unharmed by its experience.
The completeness of it is a little surprising, because laboratory tests of planarian worms have established that conditioned reflexes carry over into the new growth.
Humphries-Jacobsen experiment myself as an undergrad, training a planarian named Karen BlackI called it that because of its cute little cross-eyed faceto contract when exposed to light.
Both ends of the planarian worm elongate, and soon there are two worms, two identities, two digestive systems each as greedy as the original, each a whole, unwounded, unharmed by its experience.