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Thermotaxis
Thermotaxis is a behavior in which an organism directs its locomotion up or down a gradient of temperature. Thermotaxis is a behavior that organisms navigate on depending on the temperature. ''“Thermo”'' means heat and or the temperature and ''“taxis”'' refers to the direction or the movement. Thermotaxis is for the organism to find the best way to survive, it depends on whether it will survive in the warm or the cold. Lab research has determined that some slime molds and small nematodes (namely Meloidogyne incognita) can migrate along very shallow temperature gradients of less than 0.1°C/cm and sometimes as low as 0.001°C/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 ... [...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 Rato ... [...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. ''M. incognita'' can move along shallower temperature gradients (0.001 °C/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. Journal of Chemical Ecology. 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 ec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slime Molds
Slime mold or slime mould is an informal name given to a polyphyly, polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are near-microscopic; those in the Myxogastria form larger Plasmodium (life cycle), plasmodial slime molds visible to the naked eye. The slime mold Biological life cycle, life cycle includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic multicellular or multinucleate fruiting bodies that may be formed through aggregation or fusion; aggregation is driven by Cell signaling, chemical signals called acrasins. Slime molds contribute to the decomposition of dead vegetation; some are Parasitism, parasitic. Most slime molds are terrestrial and free-living, typically in damp shady habitats such as in or on the surface of rotting wood. Some myxogastrians and Protosteliales, protostelians are aquatic or semi-aquatic. The phytomyx ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nematodes
The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (helminths) are the cause of soil-transmitted helminthiases. They are classified along with arthropods, tardigrades and other moulting animals in the clade Ecdysozoa. Unlike the flatworms, nematodes have a tubular digestive system, 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 are uncertain. A 2013 survey of animal biodiversity suggested there are over 25,000. Estimates of the total number of extant species are subject ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
