Crossword clues for flatworm
The Collaborative International Dictionary
Flatworm \Flat"worm`\, n. (Zo["o]l.) Any worm belonging to the Platyhelminthes; also, sometimes applied to the planarians.
Wiktionary
n. Any of very many parasitic or free-living worms, of the phylum ''Platyhelminthes'', having a flattened body with no skeleton or body cavity.
WordNet
n. parasitic or free-living worms having a flattened body [syn: platyhelminth]
Wikipedia
The flatworms, flat worms, Platyhelminthes, Plathelminthes, or platyhelminths (from the Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates (having no body cavity), and have no specialized 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 (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food cannot be processed continuously.
In traditional medicinal texts, Platyhelminthes are divided into Turbellaria, which are mostly non- parasitic animals such as planarians, and three entirely parasitic groups: Cestoda, Trematoda and Monogenea; however, since the turbellarians have since been proven not to be monophyletic, this classification is now deprecated. Free-living flatworms are mostly predators, and live in water or in shaded, humid terrestrial environments, such as leaf litter. Cestodes (tapeworms) and trematodes (flukes) have complex life-cycles, with mature stages that live as parasites in the digestive systems of fish or land vertebrates, and intermediate stages that infest secondary hosts. The eggs of trematodes are excreted from their main hosts, whereas adult cestodes generate vast numbers of hermaphroditic, segment-like proglottids that detach when mature, are excreted, and then release eggs. Unlike the other parasitic groups, the monogeneans are external parasites infesting aquatic animals, and their larvae metamorphose into the adult form after attaching to a suitable host.
Because they do not have internal body cavities, Platyhelminthes were regarded as a primitive stage in the evolution of bilaterians (animals with bilateral symmetry and hence with distinct front and rear ends). However, analyses since the mid-1980s have separated out one subgroup, the Acoelomorpha, as basal bilaterians—closer to the original bilaterians than to any other modern groups. The remaining Platyhelminthes form a monophyletic group, one that contains all and only descendants of a common ancestor that is itself a member of the group. The redefined Platyhelminthes is part of the Lophotrochozoa, one of the three main groups of more complex bilaterians. These analyses had concluded the redefined Platyhelminthes, excluding Acoelomorpha, consists of two monophyletic subgroups, Catenulida and Rhabditophora, with Cestoda, Trematoda and Monogenea forming a monophyletic subgroup within one branch of the Rhabditophora. Hence, the traditional platyhelminth subgroup "Turbellaria" is now regarded as paraphyletic, since it excludes the wholly parasitic groups, although these are descended from one group of "turbellarians".
Over half of all known flatworm species are parasitic, and some do enormous harm to humans and their livestock. Schistosomiasis, caused by one genus of trematodes, is the second-most devastating of all human diseases caused by parasites, surpassed only by malaria. Neurocysticercosis, which arises when larvae of the pork tapeworm Taenia solium penetrate the central nervous system, is the major cause of acquired epilepsy worldwide. The threat of platyhelminth parasites to humans in developed countries is rising because of the popularity of raw or lightly cooked foods, and imports of food from high-risk areas. In less developed countries, people often cannot afford the fuel required to cook food thoroughly, and poorly designed water-supply and irrigation projects increase the dangers presented by poor sanitation and unhygienic farming.
Two planarian species have been used successfully in the Philippines, Indonesia, Hawaii, New Guinea, and Guam to control populations of the imported giant African snail Achatina fulica, which was displacing native snails. However, there is now concern that these planarians may themselves become a serious threat to native snails. In northwest Europe, there are concerns about the spread of the New Zealand planarian Arthurdendyus triangulatus, which preys on earthworms.
Usage examples of "flatworm".
Animals simpler than the flatworms, such as the coelenterates, sponges, and single-celled creatures, generally have either radial symmetry or no marked symmetry at all.
It swims slowly, conserving its energy, not alerting its prey, commonly flatworms and tiny-segmented creatures, predominantly isopods.
Having carried out all kinds of experiments, they finally made flatworms from the family with the sonorous name Dugesia Dorotocephala the stars of an experiment that was to lead to fantastic results.
The next more complicated group of animals are the flatworms, which, although still simple, show certain developments that foreshadow the structure of all other, more complicated, animals.
The nerve cord had to specialize, even in the flatworms, and this specialization arose, in all probability because of the shape of the flatwonn.
Even in flatworms there is an enlargement and enrichment of the nerve cord at the head end, therefore.
The originator of this research was the maverick James McConnell, at Ann Arbor, Michigan, who in a series of papers during the 1960s, first in conventional scientific journals and then in his own publication, the exotically named Worm-Runners Digest-, reported experiments in which flatworms, trained by pairing light with electric shock, were chopped up and other, 'naive' (that is, untrained) worms allowed to cannibalize them.
But flatworms don't matter, coincidences don't matter, no mundane proof matters: There is no proof that some cocksure psychiatrist could not explain away as coincidence, or déjà vu, or self-delusion.
But flatworms don’t matter, coincidences don’t matter, no mundane proof matters: There is no proof that some cocksure psychiatrist could not explain away as coincidence, or déjà vu, or self-delusion.
Maybe there'll be a new partnership out there among the starsthe descendants of free-living flatworms existing side by side in technological symbiosis with the descendants of parasitic roundworms.
As flatworms are very aphotic (averse to light), they curled up every time the lamp was switched on.
These, in turn, become food for various flatworms and numerous tiny-segmented creatures, such as isopods, which, in turn, serve as food for small, blind, white crayfish, felts and salamanders.