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The flatworms, flat worms, Platyhelminthes, or platyhelminths are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Being acoelomates, and having no specialised circulatory and respiratory organs, they are restricted 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 can not be processed continuously.
In biology, taxonomy is the scientific study of naming, defining (circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a more inclusive group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum, class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the founder of the current system of taxonomy, as he developed a ranked system known as Linnaean taxonomy for categorizing organisms and binomial nomenclature for naming organisms.
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the broomrapes.
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Thomas Spencer Cobbold FRS was an English biologist.
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A sucker in zoology is a specialised attachment organ of an animal. It acts as an adhesion device in parasitic worms, several flatworms, cephalopods, certain fishes, amphibians, and bats. It is a muscular structure for suction on a host or substrate. In parasitic annelids, flatworms and roundworms, suckers are the organs of attachment to the host tissues. In tapeworms and flukes, they are a parasitic adaptation for attachment on the internal tissues of the host, such as intestines and blood vessels. In roundworms and flatworms they serve as attachment between individuals particularly during mating. In annelids, a sucker can be both a functional mouth and a locomotory organ. The structure and number of suckers are often used as basic taxonomic diagnosis between different species, since they are unique in each species. In tapeworms there are two distinct classes of suckers, namely "bothridia" for true suckers, and "bothria" for false suckers. In digeneal flukes there are usually an oral sucker at the mouth and a ventral sucker posterior to the mouth. Roundworms have their sucker just in front of the anus; hence it is often called a pre-anal sucker.
References
- ↑ Macleay, William Sharp (1819). Horae entomologicae : or, Essays on the annulose animals (PDF).
- ↑ Cobbold, Thomas Spencer (1869). Entozoa: an introduction of the study of helminthology, with reference to the internal parasites of man.
- ↑ Egerton, Frank N. (2013). "History of Ecological Sciences, Part 46: From Parasitology to Germ Theory". The Bulletin of the Ecological Society of America. 94 (2): 136–164. Bibcode:2013BuESA..94..136E. doi:10.1890/0012-9623-94.2.136.
- ↑ Torre-Bueno, J. R. de la (1989). The Torre-Bueno Glossary of Entomology (PDF). New York Entomological Society. ISBN 0-913424-13-7.
- ↑ Jordan, Robert C. R. (1855). "On the Entozoa, Especially Those Infesting the Human Subject: Bring the Substance of a Lecture Given at Queen's College". Association Medical Journal. 3 (139): 809–812. JSTOR 25496610.