planarian

pla·nar·i·an

P0347700 (plə-nâr′ē-ən)n. Any of various small, chiefly freshwater flatworms of the order Tricladida, having a soft, broad, ciliated body, a three-branched digestive cavity, and the ability to regenerate body parts.

[From New Latin Plānāria, genus name, from feminine of Late Latin plānārius, on level ground, from plānus, flat; see pelə- in Indo-European roots.]

planarian

(pləˈnɛərɪən) n (Animals) any free-living turbellarian flatworm of the mostly aquatic suborder Tricladida, having a three-branched intestine[C19: from New Latin Plānāria type genus, from Late Latin plānārius level, flat; see plane¹]

pla•nar•i•an

(pləˈnɛər i ən)

n. any of various free-swimming, mostly freshwater flatworms, having an undulating or sluglike motion. [1885–60; < New Latin Planari(a) a flatworm genus (n. use of feminine of Late Latin plānārius level, on level ground; taken to mean “flat”; see plane¹, -ary) + -an¹]

Thesaurus

Noun

planarian - free-swimming mostly freshwater flatworms; popular in laboratory studies for the ability to regenerate lost partsplanariaflatworm, platyhelminth - parasitic or free-living worms having a flattened bodyclass Turbellaria, Turbellaria - free-living flatworms

planarian

planarian,

common name for several genera of the free-living (turbellarian) flatworms belonging to the order Tricladida, a name that derives from their characteristic three-branched digestive cavities. Most species range from 1-8 in. to about 1 in. in length (.32–2.54 cm) although some giant tropical forms range up to 2 ft. (60 cm). The different species are generally white, gray, brown, or black; a few forms are transparent. Many are striped or streaked and some of the large terrestrial species are brightly colored. Although planarians can be found in marine or moist terrestrial habitats, most inhabit freshwater areas. They crawl about over a trail of mucus that is secreted by specialized epidermal cells; the smaller forms move about by means of cilia on their ventral, or lower, surface, and larger species utilize muscular contractions as well. Tactile and chemoreceptive cells, located in the epidermis, serve as general sense organs. In many species these cells are clumped in lobes at the sides of the head. Most planarians are also light-sensitive and in some, pigmented light-sensitive cells are clumped in two cups that serve as primitive eyes. Planarians are usually either carnivorous or scavengers. The mouth is located near the middle of the ventral surface. The tubelike pharynx can be everted from the mouth and inserted into the prey; food is partially digested externally before it is sucked into the gut. Planarians are hermaphroditic; each individual worm contains both male and female organs, and, most commonly, they reproduce sexually. However, species similar to the 1/2-in.-long (1.27-cm) Dugesia tigrina, the most common planarian in the United States, are much studied in classrooms and laboratories for their additional capacity to reproduce asexually by transverse rupture of the body: a rupture line develops behind the mouth, and while the back half of the worm is anchored, the front half moves forward until the worm snaps in half. Each half regenerates the missing parts. Such planarians can also regenerate parts that are cut from the body. Planarians are classified in the phylum PlatyhelminthesPlatyhelminthes
, phylum containing about 20,000 species of soft-bodied, bilaterally symmetrical, invertebrate animals, commonly called flatworms. There are four classes: the free-living, primarily aquatic class, Turbellaria, and Trematoda, Cestoda, and Monogenea, which are
..... Click the link for more information. , class Turbellaria, order Tricladida.

planarian

pla·nar·i·an

planarian

pla•nar•i•an

planarian

planarian,

planarian

planarian

planarian

Synonyms for planarian

noun free-swimming mostly freshwater flatworms

Synonyms

Related Words