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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.
Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and include two main classes: Enteropneusta, and Pterobranchia. A third class, Planctosphaeroidea, is known only from the larva of a single species, Planctosphaera pelagica. The class Graptolithina, formerly considered extinct, is now placed within the pterobranchs, represented by a single living genus Rhabdopleura.
Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is known as a bud. Since the reproduction is asexual, the newly created organism is a clone and excepting mutations is genetically identical to the parent organism. Organisms such as hydra use regenerative cells for reproduction in the process of budding.
Planarians (triclads) are free-living flatworms of the class Turbellaria, order Tricladida, which includes hundreds of species, found in freshwater, marine, and terrestrial habitats. Planarians are characterized by a three-branched intestine, including a single anterior and two posterior branches. Their body is populated by adult stem cells called neoblasts, which planarians use for regenerating missing body parts. Many species are able to regenerate any missing organ, which has made planarians a popular model in research of regeneration and stem cell biology. The genome sequences of several species are available, as are tools for molecular biology analysis.
Fragmentation in multicellular or colonial organisms is a form of asexual reproduction or cloning, where an organism is split into fragments upon maturation and the spilted part becomes the new individual.
Botryllus schlosseri is a colonial ascidian tunicate. It is commonly known as the star tunicate, but it also has several other common names, including star ascidian and golden star tunicate. Colonies grow on slow-moving, submerged objects, plants, and animals in nearshore saltwater environments.
Corynactis californica is a brightly colored colonial anthozoan corallimorph. Unlike the Atlantic true sea anemone, Actinia fragacea, that bears the same common name, strawberry anemone, this species is a member of the order Corallimorpharia, and is the only member found in the North American West Coast. Other common names include club-tipped anemone and strawberry corallimorpharian. The anemone can live up to at least 50 meters (160 ft) deep on vertical rock walls, and at the bottom of kelp forests. It is known to carpet the bottom of some areas, like Campbell River in British Columbia, and Monterey Bay in California.
Dromia personata, also known as the sponge crab or sleepy crab, is a species of crab found in the North Sea, the Mediterranean Sea, and connecting parts of the northeastern Atlantic Ocean. Like most other epibenthic crustaceans, the biomass of this species is especially dense in the Mediterranean continental shelf. It mainly resides from the lower shore to a depth of 50 meters (164 ft), often in caves. Occasionally, they are found living in depths as low as 110 meters (360 ft). They serve as prey for octopus, starfish, and other fish. Their last two pairs of legs are positioned dorsally, and are used to hold a sponge in place as camouflage.
Lamellibrachia luymesi is a species of tube worms in the family Siboglinidae. It lives at deep-sea cold seeps where hydrocarbons are leaking out of the seafloor. It is entirely reliant on internal, sulfide-oxidizing bacterial symbionts for its nutrition. These are located in a centrally located "trophosome".
Alitta succinea is a species of marine annelid in the family Nereididae. It has been recorded throughout the North West Atlantic, as well as in the Gulf of Maine and South Africa.
Clavelina picta, common name the painted tunicate, is a species of tunicate, in the genus Clavelina. These animals, like all ascidians, are sessile filter feeders.
Berghia is a genus of sea slugs, aeolid nudibranchs. They are shell-less marine gastropod molluscs in the family Aeolidiidae. They are covered in cerata which give them their unique tentacle look and color. Berghia are commonly found in shallow waters and their diet consists of strictly Aiptasia Anemone. This genus is now commonly used commercially to fight off Anemone populations in fish tanks.
Convolutriloba is a genus of marine acoelomorph worms.
In biology, Gonozooids are any of the reproductive individuals of Tunicates, Bryozoan, or Hydrozoan colonies that produce gametes. Gonozooids may play a role in labour division or in alternation of generations. A gonozooid typically has hardly any other function than reproduction, amounting to little more than a motile gonad.
Polypodium is a genus of cnidarians that parasitizes in the eggs of sturgeon and similar fishes. It is one of the few metazoans (animals) that live inside the cells of other animals.
Physonectae is a suborder of siphonophores. In Japanese it is called 胞泳.
Ophionereis schayeri, Schayer's brittle star, is a brittle star in the family Ophionereididae.
Echinaster is a well-studied and common genus of starfish containing ~30 species and is the second-largest genus found within the family Echinasteridae. The genera Henricia and Echinaster encompass 90% of all the species found within the family Echinasteridae. It contains 30 species, however the number of species in this genus is still debatable because of uncertainty within the genera. This genus is currently sub-divided into two sub-genera: Echinaster and Othilia, evolutionary relationships between the sub-genera is not understood. Echinaster are found in the Pacific, Atlantic and Indian oceans, with most species being studied in the Gulf of Mexico and Brazil. The sub-genera Othilia is thought to encompass species mainly found in the Gulf of Mexico and Brazil. Echinaster is often one of the most studied species within the family Echinasteridae and is often used to find evolutionary relationships.
Ophiothela mirabilis is a species of ophiuroid brittle star within the family Ophiotrichidae. O. mirabilis is an epizoic species which have a non-parasitic relationship with host sponges or gorgonians. Although native to the Pacific Ocean, it has invaded the Caribbean and southwestern Atlantic since late 2000. Many of its characteristics, including reproduction and diet, allow O. mirabilis opportunities to quickly propagate and spread through habitats.
Paranemertes peregrina is a species of Nemertea, or ribbon worm, in the family Neesiidae.
References
- 1 2 Åkesson, Bertil; Robert Gschwentner; Jan Hendelberg; Peter Ladurner; Johann Müller; Reinhard Rieger (2001-12-01). "Fission in Convolutriloba longifissura: asexual reproduction in acoelous turbellarians revisited" (PDF). Acta Zoologica. 82 (3): 231–239. doi:10.1046/j.1463-6395.2001.00084.x. ISSN 1463-6395. Archived from the original (PDF) on 2016-03-04. Retrieved 2011-07-13.
- ↑ Egger, Bernhard (December 2008). "Regeneration: rewarding, but potentially risky" (PDF). Birth Defects Research Part C: Embryo Today: Reviews. 84 (4): 257–264. doi:10.1002/bdrc.20135. ISSN 1542-9768. PMID 19067421 . Retrieved 2011-07-13.
- 1 2 Herlant-Meewis, Henriette (1950-10-01). "Cyst-Formation in Aeolosoma Hemprichi (Ehr)". Biological Bulletin. 99 (2): 173–180. doi:10.2307/1538737. ISSN 0006-3185. JSTOR 1538737. PMID 14791418.
- ↑ Jaeckle, William B. (1994-02-01). "Multiple Modes of Asexual Reproduction by Tropical and Subtropical Sea Star Larvae: An Unusual Adaptation for Genet Dispersal and Survival". Biological Bulletin. 186 (1): 62–71. doi:10.2307/1542036. ISSN 0006-3185. JSTOR 1542036. PMID 29283296.
- ↑ Raikova, Ekaterina V. (1994-02-01). "Life Cycle, Cytology, and Morphology of Polypodium hydriforme, a Coelenterate Parasite of the Eggs of Acipenseriform Fishes". The Journal of Parasitology. 80 (1): 1–22. doi:10.2307/3283338. ISSN 0022-3395. JSTOR 3283338. PMID 7905920.