Биологиялық электр және электрорецепция қабілеттері

Biological electricity related abilities

Electroreception and electrogenesis are the closely related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes (most famously the electric eel, which is not actually an eel but a knifefish) to stun prey. The capabilities are found almost exclusively in aquatic or amphibious animals, since water is a much better conductor of electricity than air. In passive electrolocation, objects such as prey are detected by sensing the electric fields they create. In active electrolocation, fish generate a weak electric field and sense the different distortions of that field created by objects that conduct or resist electricity. Active electrolocation is practised by two groups of weakly electric fish, the Gymnotiformes (knifefishes) and the Mormyridae (elephantfishes), and by Gymnarchus niloticus, the African knifefish. An electric fish generates an electric field using an electric organ, modified from muscles in its tail. The field is called weak if it is only enough to detect prey, and strong if it is powerful enough to stun or kill. The field may be in brief pulses, as in the elephantfishes, or a continuous wave, as in the knifefishes. Some strongly electric fish, such as the electric eel, locate prey by generating a weak electric field, and then discharge their electric organs strongly to stun the prey; other strongly electric fish, such as the electric ray, electrolocate passively. The stargazers are unique in being strongly electric but not using electrolocation. The electroreceptive ampullae of Lorenzini evolved early in the history of the vertebrates; they are found in both cartilaginous fishes such as sharks, and in bony fishes such as coelacanths and sturgeons, and must therefore be ancient. Most bony fishes have secondarily lost their ampullae of Lorenzini, but other non homologous electroreceptors have repeatedly evolved, including in two groups of mammals, the monotremes (platypus and echidnas) and the cetaceans (Guiana dolphin).

[[File:Gymnarchus niloticus005 (cropped). JPG|thumb|upright=1.3|Hans Lissmann discovered electroreception in 1950 through his observations of Gymnarchus niloticus. The electroreceptive function of these organs was established by R. W. Murray in 1960. In 1921, the German anatomist Viktor Franz described the knollenorgans (tuberous organs) in the skin of the elephantfishes, again without knowledge of their function as electroreceptors. In 1949, the Ukrainian British zoologist Hans Lissmann noticed that the African knife fish (Gymnarchus niloticus) was able to swim backwards at the same speed and with the same dexterity around obstacles as when it swam forwards, avoiding collisions. He demonstrated in 1950 that the fish was producing a variable electric field, and that the fish reacted to any change in the electric field around it.

In vertebrates, passive electroreception is an ancestral trait, meaning that it was present in their last common ancestor. The ancestral mechanism is called ampullary electroreception, from the name of the receptive organs involved, ampullae of Lorenzini. These evolved from the mechanical sensors of the lateral line, and exist in cartilaginous fishes (sharks, rays, and chimaeras), lungfishes, bichirs, coelacanths, sturgeons, paddlefishes, aquatic salamanders, and caecilians. Ampullae of Lorenzini appear to have been lost early in the evolution of bony fishes and tetrapods, though the evidence for absence in many groups is incomplete and unsatisfactory. Passively electrolocating groups, including those that move their heads to direct their electroreceptors, are shown without symbols. Non electrolocating species are not shown. Fish able to deliver electric shocks are marked with a red lightning flash 20px.

Two groups of teleost fishes are weakly electric and actively electroreceptive: the Neotropical knifefishes (Gymnotiformes) and the African elephantfishes (Notopteroidei), enabling them to navigate and find food in turbid water.

[[File:Platypus electrolocation. svg|thumb|left|upright=2.5|The platypus is a monotreme mammal that has secondarily acquired electroreception. Its receptors are arranged in stripes on its bill, giving it high sensitivity to the sides and below; it makes quick turns of its head as it swims to detect prey. The platypus localises its prey using almost 40,000 electroreceptors arranged in front to back stripes along the bill. The arrangement is highly directional, being most sensitive off to the sides and below. By making short quick head movements called saccades, platypuses accurately locate their prey. The platypus appears to use electroreception along with pressure sensors to determine the distance to prey from the delay between the arrival of electrical signals and pressure changes in water. Experiments have shown that echidnas can be trained to respond to weak electric fields in water and moist soil. The electric sense of the echidna is hypothesised to be an evolutionary remnant from a platypus like ancestor.

Until recently, electroreception was known only in vertebrates. Recent research has shown that bees can detect the presence and pattern of a static charge on flowers.