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Thermotaxis
Thermotaxis is a behavior in which an organism directs its locomotion up or down a gradient of temperature. Lab research has determined that some slime molds and small nematodes (namely Meloidogyne incognita) can migrate along amazingly shallow temperature gradients of less than 0.1C/cm and sometimes as low as 0.001C/cm. Theoretical analysis indicates that even this impressive feat is far from pushing the limits set by thermal noise. The natural environment always contains temperature gradients that organisms could respond to, if it were useful. The response of the slime mold and nematode is complicated and thought to allow them to move toward an appropriate level in soil.Dusenbery, David B. (1996). “Life at Small Scale”, pp. 101-109. Scientific American Library, New York. . Recent research suggests that mammalian sperm employ thermotaxis to move to an appropriate location in the female's oviduct (see Sperm guidance Sperm guidance is the process by which sperm cells (spermatoz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperm Guidance
Sperm guidance is the process by which sperm cells (spermatozoa) are directed to the oocyte (egg) for the aim of fertilization. In the case of marine invertebrates the guidance is done by chemotaxis. In the case of mammals, it appears to be done by chemotaxis, thermotaxis and rheotaxis. Background Since the discovery of sperm attraction to the female gametes in ferns over a century ago, sperm guidance in the form of sperm chemotaxis has been established in a large variety of speciesMiller, R.L. (1985) ''Sperm chemo-orientation in the metazoa''. In: ''Biology of Fertilization'' (Metz, C.B. and Monroy, A., eds.), pp. 275–337. Academic Press, New York. Although sperm chemotaxis is prevalent throughout the Metazoa kingdom, from marine species with external fertilization such as sea urchins and corals, to humans,Cosson, M.P. (1990) ''Sperm chemotaxis''. In: ''Controls of Sperm Motility: Biological and Clinical Aspects'' (Gagnon, C., ed.) pp. 103–135. CRC Press, Boca Raton, FL.Eise ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slime Molds
Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic multicellular or multinucleate fruiting bodies which may be formed through aggregation or fusion. Slime molds were formerly classified as fungi but are no longer considered part of that kingdom. Although not forming a single monophyletic clade, they are grouped within the paraphyletic group Protista. More than 900 species of slime mold occur globally. Their common name refers to part of some of these organisms' life cycles where they can appear as gelatinous "slime". This is mostly seen with the Myxogastria, which are the only macroscopic slime molds. Most slime molds are smaller than a few centimetres, but some species may reach sizes up to several square metres and masses up to 20 kilograms. They feed on microorganisms that live in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nematodes
The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broad range of environments. Less formally, they are categorized as Helminths, but are taxonomically classified along with arthropods, tardigrades and other moulting animals in the clade Ecdysozoa, and unlike flatworms, have tubular digestive systems with openings at both ends. Like tardigrades, they have a reduced number of Hox genes, but their sister phylum Nematomorpha has kept the ancestral protostome Hox genotype, which shows that the reduction has occurred within the nematode phylum. Nematode species can be difficult to distinguish from one another. Consequently, estimates of the number of nematode species described to date vary by author and may change rapidly over time. A 2013 survey of animal biodiversity published in the mega jo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meloidogyne Incognita
''Meloidogyne incognita'' (root-knot nematode - RKN), also known as the "southern root-nematode" or "cotton root-knot nematode" is a plant-parasitic roundworm in the family Heteroderidae. This nematode is one of the four most common species worldwide and has numerous hosts. It typically incites large, usually irregular galls on roots as a result of parasitism. ''Meloidogyne incognita'' can move along shallower temperature gradients (0.001C/cm) than any other known organism, an example of thermotaxis. The response is complicated and thought to allow the nematodes to move toward an appropriate level in soil, while they search for chemical cues that can guide them to specific roots.Diez and Dusenbery. 1989. Repellent of root-knot nematodes from the exudate of host roots. J. Chem. Ecol. 15:2445-2455. Distribution ''Meloidogyne incognita'' is widely spread around the globe and found in many different soil types. Host ''Meloidogyne incognita'' is probably the most economically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
