Taxis
Encyclopedia
A taxis is an innate behavior
Behavior
Behavior or behaviour refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with its environment, which includes the other systems or organisms around as well as the physical environment...

al response by an organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

 to a directional stimulus
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....

 or gradient of stimulus intensity. A taxis differs from a tropism
Tropism
A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus...

 (turning response, often growth towards or away from a stimulus) in that the organism has motility
Motility
Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...

 and demonstrates guided movement towards or away from the stimulus source . It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.

Examples

For example, flagellate protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

ns of the genus Euglena
Euglena
Euglena is a genus of unicellular flagellate protists. It is the best known and most widely studied member of the phylum Euglenozoa , a diverse group containing some 44 genera and at least 800 species. Species of Euglena are found in fresh and salt waters...

 move towards a light source. Here the directional stimulus is light, and the orientation movement is towards the light. This reaction or behaviour is a positive one to light and specifically termed "positive phototaxis", since phototaxis is a response to a light stimulus, and the organism is moving towards the stimulus. If the organism moves away from the stimulus, then the taxis is negative. Many types of taxis have been identified and named using prefixes to specify the stimulus that elicits the response. These include aerotaxis (stimulation by oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

) anemotaxis (wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

), barotaxis (pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

), chemotaxis
Chemotaxis
Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...

 (chemicals), galvanotaxis (electrical current), gravitaxis (gravity), hydrotaxis (moisture
Moisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...

), magnetotaxis
Magnetotaxis
Logically, magnetotaxis describes an ability to sense a magnetic field and coordinate movement in response. It was applied to the behavior of certain motile, aquatic bacteria in 1975 by R. P. Blakemore....

 (magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

), phototaxis
Phototaxis
Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves in response to the stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis...

 (light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

), rheotaxis
Rheotaxis
Rheotaxis is a form of taxis seen in many aquatic organisms, e.g., fish, whereby they will turn to face into an oncoming current...

 (fluid flow), thermotaxis (temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 changes) and thigmotaxis (physical contact
Somatosensory system
The somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...

).

Depending on the type of sensory organs present, taxes can be classified as klinotaxes, where an organism continuously samples the environment to determine the direction of a stimulus, tropotaxes, where bilateral sense organs are used to determine the stimulus direction, and telotaxes, which are similar to tropotaxes but where a single organ suffices to establish the orientation movement.

Aerotaxis

Aerotaxis is the response of an organism to variation in oxygen concentration, and is mainly found in aerobic bacteria.

Chemotaxis

Chemotaxis is a migratory response that is elicited by chemicals: that is, a response to a chemical concentration gradient. For example, chemotaxis in response to a sugar gradient has been observed in motile bacteria such as E. Coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

. Chemotaxis also occurs in the antherozoids
Antheridium
An antheridium or antherida is a haploid structure or organ producing and containing male gametes . It is present in the gametophyte phase of lower plants like mosses and ferns, and also in the primitive vascular psilotophytes...

 of liverworts
Marchantiophyta
The Marchantiophyta are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information....

, fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s, and mosses in response to chemicals secreted by the archegonia
Archegonium
An archegonium , from the ancient Greek ἀρχή and γόνος , is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female gamete. The archegonium has a long neck canal and a swollen base...

.

Unicellular (e.g. protozoa) or multicellular (e.g. worms) organisms are targets of chemotactic substances. A concentration gradient of chemicals developed in a fluid phase guides the vectorial movement of responder cells or organisms. Inducers of locomotion towards increasing steps of concentrations are considered as chemoattractants, while chemorepellents result moving off the chemical. Chemotaxis is described in prokaryotic
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

 and eukaryotic
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

 cells, but signalling mechanisms (receptors, intracellular signaling) and effectors are significantly different.

Energy taxis

Energy taxis is the orientation of bacteria towards conditions of optimal metabolic activity by sensing the internal energetic
conditions of cell. Therefore in contrast to chemotaxis (taxis towards or away from a specific extracellular compound), energy taxis responds on an intracellular stimulus (e.g. proton motive force, activity of NDH- 1
NADH dehydrogenase
NADH dehydrogenase is an enzyme located in the inner mitochondrial membrane that catalyzes the transfer of electrons from NADH to coenzyme Q...

) and requires metabolic activity.

Phototaxis

Phototaxis is the movement of an organism in response to light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

: that is, the response to variation in light intensity and direction.
  • Negative phototaxis, or movement away from a light source, is demonstrated in some insects, such as cockroaches.
  • Positive phototaxis, or movement towards a light source, is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis
    Photosynthesis
    Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

    . Many phytoflagellates, e.g. Euglena
    Euglena
    Euglena is a genus of unicellular flagellate protists. It is the best known and most widely studied member of the phylum Euglenozoa , a diverse group containing some 44 genera and at least 800 species. Species of Euglena are found in fresh and salt waters...

    , and the chloroplast
    Chloroplast
    Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

    s of higher plants positively phototactic, moving towards a light source. Two types of positive phototaxis are observed in prokaryotes.
  1. Scotophototaxis is observable as the movement of a bacterium out of the area illuminated by a microscope. Entering darkness signals the cell to reverse direction and reenter the light.
  2. A second type of positive phototaxis is true phototaxis, which is a directed movement up a gradient to an increasing amount of light.

Thermotaxis

Thermotaxis is a migration along a gradient of temperature. Some slime molds and small nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s can migrate along amazingly small temperature gradients of less than 0.1C/cm. They apparently use this behavior to move to an optimal level in soil.

Gravitaxis

Gravitaxis (known historically as geotaxis) is a response to the attraction due to gravity. The plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

ic larvae of the king crab
King crab
King crabs, also called stone crabs, are a superfamily of crab-like decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab, Paralithodes camtschaticus.King...

 Lithodes aequispinus use a combination of positive phototaxis (movement towards the light) and negative gravitaxis (upward movement) . Both positive and negative gravitaxes are found in a variety of protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

ns .

Rheotaxis

Rheotaxis is a response to a current
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...

 in a fluid. Positive rheotaxis is shown by fish turning to face against the current. In a flowing stream, this behavior leads them to hold their position in a stream rather than being swept downstream. Some fish will exhibit negative rheotaxis where they will avoid currents.

Magnetotaxis

Logically, magnetotaxis is the ability to sense a magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

 and coordinate movement in response. However, the term is commonly applied to bacteria that contain magnets and are physically rotated by the force of the Earth's magnetic field. In this case, the "behavior" has nothing to do with sensation, and the bacteria are more accurately described as "magnetic bacteria".

Galvanotaxis / electrotaxis

Galvanotaxis or electrotaxis is directional movement of motile cells in response to an electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

. It has been suggested that by detecting and orientating themselves toward the electric fields, cells are able to direct their movement towards the damages or wounds to repair the defect. It also is suggested that such a movement may contribute to directional growth of cells and tissues during development and regeneration. This notion is based on 1) the existence of measurable electric fields that naturally occur during wound healing, development and regeneration; and 2) cells in cultures respond to applied electric fields by directional cell migration – electrotaxis / galvanotaxis.

Thigmotaxis

Thigmotaxis is the response of an organism to physical contact, or to the proximity of a physical discontinuity in the environment (e.g. rats preferring to swim near the edge of a water maze).

Terminology regarding direction of taxis

Based on classification of finding path the taxis may be classified into following 5 types:

Klinotaxis

Klinotaxis occur in organisms with receptor cells but no paired receptor organs. The cells for reception are located all over the body, particularly towards the anterior side. The organisms detect the stimuli
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....

 by turning their head sideways and compare the intensity. When the intensity of stimuli is balanced equally from all sides then the organisms move in a straight line. Examples: movement of larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

 of blowfly and butterfly
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...

.

Tropotaxis

Tropotaxis are displayed by organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s with paired receptor cells. When the stimuli coming from a source is balanced equally the organisms show movement. In this animals are capable of showing sideways movement unlike klinotaxis where the organisms show movement in a straight line. Example: movement of Greyling butterfly
Grayling (butterfly)
The Grayling is a species in the brush-footed butterfly family Nymphalidae. It sometimes occurs in coastal areas of northeast Scotland such as the Fowlsheugh Nature Reserve. It can also be found near the coast around England, such as Fire Beacon Hill...

, fish louse

Telotaxis

Teleotaxis require paired receptors. The movement occurs along the direction where the intensity of the stimuli is stronger. For example: when bee
Bee
Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila...

s move from their hive
Hive
A hive may refer to a beehive, an enclosed structure in which some honey bee species live and raise their young.Hive may also refer to:-Arts:* The Hives, a Swedish rock band* Hive , a DJ and producer in the drum and bass music genre...

 for food they balance the stimuli from the sun as well as flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

 but reside on the flower whose intensity is higher for them.

Menotaxis

Menotaxis In this constant angular orientation of the organisms takes place. Example: Bees returning to their hive at night, movement of ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...

 with response to the sun.

Mnemotaxis

Mnemotaxis are a complex type of stimuli. In this the organisms pick up the trails left by them when traveling back to their home. Thus this is a memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

 response of an organisms.

See also

  • Animal locomotion
    Animal locomotion
    Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...

  • Optomotor response
    Optomotor response
    The optomotor response is an innate behaviour common to fish and all insects. It serves for course stabilization during free locomotion through an involuntary displacement from a straight course. The purpose of this behaviour is to regain the desired course of locomotion....

  • Haptotaxis
    Haptotaxis
    Haptotaxis is the directional motility or outgrowth of cells, e.g. in the case of axonal outgrowth, usually up a gradient of cellular adhesion sites or substrate-bound chemoattractants...

  • Mechanotaxis
    Mechanotaxis
    Mechanotaxis refers to the directed movement of cell motility via mechanical cues...

  • Tropism
    Tropism
    A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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