Statoliths, otoliths ( "ear stones " ), otoconia or Statoconia are microscopic grains to several centimeters large stones of solid material ( for example, lime or starch ) that are found in protozoa and in the management and balance organs of many other species. Due to its inertial mass and its weight they enable the organism, accelerations ( dynamic) and perceive the direction of gravity (static). The term otolith refers on the one hand to the fact that these structures are in vertebrates in the inner ear, on the other hand they serve at many fish the hearing. As otoconia in the narrow sense refers to the existing calcium carbonate biominerals in mammals.
Can statoliths In multicellular organisms, in Statozysten freely lie ( then take the lowest point of the room and press the respectively located at this point sensory cells ), or they can be attached to the hairs of the sensory cells (and thus the direction to the center of the earth Show ). Here are perceived shear pressure, and train. The reflexes that are triggered by the gravity - sense organs, cause the animal to maintain its normal position in space.
Two sacs of the membranous labyrinth - - In mammals, the utricle and saccule contain structures in the inner ear statoliths of so-called auditory sand ( calcite crystals) in a gel-like matrix of organic material. These gel lumps ( otoconia ) the stereocilia of the hair cells stick in the cave wall. Transferred relative movements of statoliths to the hairs and produce sensory stimuli. As otoconia refers to the essential, non-cellular constituents above the vestibular sensory cells of the utricle and saccule in the vestibular organ of mammals. They are there embedded in a gelatinous mass (matrix) of organic material. Otoconia are among the biominerals, that is, Structures of inorganic materials (minerals ) and organic ( biomolecules ), in a self-organized growth process of living organisms for specific functions (eg balance ) are formed. Otoconia chemically consist mainly of calcite, a stable modification of calcium carbonate and organic components ( <5%, for example, glycoproteins and calcium- binding proteins). At the nanoscale show human otoconia structurally defined inorganic / organic subunits ( nanocomposite ) of different order (mosaic structure). Otoconia are therefore characterized as mosaic- controlled nanocomposite. The internal structure consists of a dumbbell-shaped, dense volume and nano- structurally more ordered dumbbell-shaped structure ( " branches "), which is surrounded by a less dense, nano- structurally less-ordered external structure ( "belly ").
In fish, the otoliths three on each side ( lapillus in the utricle, saccule and Sagitta in Asteriscus in the lagena ) are usually only a few millimeters in size, but may also be a few centimeters long ( for example, the Sagittae the eagle fish). They are composed of aragonite or vaterite with a protein content ( Otolin ) from 0.2 to 10 percent and can be used to determine the age, as they while growing an onion shell structure with daily, but at least ( in areas with distinct seasons ) Annual rings ( s form. annulus ). The otoliths of the sacculus and the lagena serve in teleosts mainly the sense of hearing and are therefore very large and sometimes interconnected. The Sagittae are often flattened oval and laterally. They have mostly external appendages, inside they are relatively smooth and have regular patterns. The latter can ( and many others around at Umberfischen ) even a species identification to and, not least in fossils, interesting questions regarding the origin of bony fishes.
In plants provide amyloplasts in Statocyten that are located in the root cap, statoliths dar. This will help the plant roots in the direction of center of the earth to grow. The tendency to grow center of the earth depends on the type of root and its order.
Artificial ( biomimetic ) otoconia
The research group led by Kniep et al. from the Max Planck Institute for Chemical Physics of Solids in Dresden in 2008, it is the first time succeeded in manufacturing artificial ( biomimetic ) otoconia ( calcite - gelatine - composite ) in vivo. On the basis of these studies, in which human and artificial otoconia the drug gentamicin sulfate were suspended in vitro could be demonstrated that the principal morphological, chemical and physical properties of human and biomimetic otoconia are identical. This assumption was confirmed by studies of the solution behavior of human and artificial otoconia in gentamicin exposure. Walther et al. have shown that artificial ( biomimetic ) otoconia are useful as a model system to open questions, such as elucidate structural changes, such as those caused by degenerative changes ( benign paroxysmal positional vertigo ) or can occur as a result of ototoxic drugs in otoconia.