Rhinophore
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Rhinophores ( altgr. ῥίς ( rhis ) = nose, φορος ( phoros ) = supporting) form an olfactory sense organ that artabhängige a selection of chemical substances such as Fragrances, flavors, pheromones recognizes. They occur, inter alia, with slugs and sea snails ( Opisthobranchia ) the order of the nudibranch ( Nudisbranchia ), in particular at the doriden nudibranchs. The sense organ consists of chemoreceptors, biological sensors with which substances are observed from input neurons to the nervous system, inducing the receptors for transmitting signals for perceived substances, and a pair of sensor, which is located in a prominent position on the top of the head and houses receptors as input neurons.
- 2.1 Mobility of rhinophores
- 2.2 Olfactory perception
- 2.3 form of rhinophores
Case study on Aplysia californica
The basic structure of rhinophores is here described the much studied genus of sea hare Aplysia californica using the example of the sort.
Function
The Alypsia the rhinophores of remote viewing of substances such as fragrances and flavorings as well as the Rheorezeption serve (perception of water flow ).
A large number of chemoreceptors on the surface of the rhinophores allows a fine perception, with the help of which the snail find food sources.
Construction
In Aplysia, the rhinophores are a pair of rod antennas that are based on the surface of the top of the head. Compared to the size of the animal, the rhinophores are usually quite small: in a full blown Aplysia californica was its length is only about 1 cm.
The physical perception center of the rhinophores is in a groove at the tip. The performance via specialized hair cells ( ciliated cells ) or protuberances (small protrusions ) on the surface of the outer fabric. These hair cells are chemoreceptors for fragrances and flavors.
The input to the nervous system via neurons in the tissue (epithelium ) are incorporated in the groove area. The dendrites of these neurons are connected to the hair cells and prominences. In perception of substances through the receptor cells on the surface, the neurons are activated. The neurons are derived, the input signal then their axons to Rhinophorenganglion (collection of nerve cells in the nervous system and processing center of the screw ) on ( projected).
In the throat near the Aplysia californica have tentacles that are also occupied with receptor cells and are used to sense perception. It is, however, of any function overlap from, but thinks the tentacle receptors are more chemo-or mechanoreceptors for touch perception.
Extensions
Based on the Alypsia californica the main elements of olfactory perception have been shown by rhinophores: Antenna - Chemoprezeptoren - input neurons - nervous system - ganglia. These elements and the signal path remain the same for all species of snails with rhinophores. However, there is variability in the states, will be made aware of the.
Mobility of rhinophores
The above picture of Chromodoris coi suggests that rhinophores are not only rigid attachments. In fact, some snails can align their rhinophores in different directions.
The antenna shape of the rhinophores is good for the tasks to be accomplished, but at the same time makes it to sensitive points of attack for their natural enemies: the rhinophores are easy to tear off, on or erode. To avoid this, most doriden nudibranchs are able to feed their rhinophores in pockets below the skin surface.
Olfactory perception
Compared to the visual and auditory senses, the olfactory perception to some differences.
Vision and hearing based on waves (light, sound waves). Waves propagate relatively quickly and evenly. The signal transmission follows the domino principle. You will come across a chain of dominoes at all dominoes remain in place, but change its status from " standing ", " like " in, and the last falling stone tells the recipient that the sender has initiated the chain before. So physically transfer are physical states, but not components. Furthermore, relatively just a few types of receptor cells for exercise. In the human eye, for example, are Rod cells for the nocturnal light-dark vision and three types of cone cells for filtering out frequency bands ( proportion of red, green, blue light) when tags marriages responsible.
In the olfactory perception fluctuating molecules of chemical substances from the medium ( water) must be filtered out and assigned. The filtering is often done by docking and entering into chemical bonds, which then trigger an internal signal chain. For the " recognition" of many substances, therefore, a sufficiently broad spectrum of receptor cells requires ( a man has ~ 320 chemoreceptors, a Sheepdog ~ 1200). The signal is transmitted over the physical transfer of molecules from origin to Wahrnehmungsort. Molecules, however, (eg, compared to electrons) quite large and vulnerable to barriers. Secondly, they are subject to the signal path influences the transport medium (eg currents ). Chemical signals are, therefore, if they are not very strong, diffuse and not as focused as light and sound waves.
From this we can formulate general quality criteria for olfactory senses: 1) per type of chemoreceptor should be as many receptors available, 2) the receptors should not be as concentrated as possible at points but be sensible spatially distributed, 3) the more types of chemoreceptors, the better the perception. In the space well distributed receptor sites with good enforcement of various types are therefore desirable.
Form of rhinophores
In the Sea Slug Forum diverse forms of rhinophores are shown. These differ both in the form of sensory areas in the position and shape of the antenna. Under the above considerations one can evaluate the forms of spawned rhinophores.
Many rhinophores have a basic form two rod antennas with attached sensory fields. Rod antennas are simple, flexible structures. You can be tilted in various directions, rotated and ein-/ausgefahren for protection purposes. On the other hand, the antennas themselves are not a lot of ground.
The above pictures of the Canthodoris pilosa, Chromodoris annulata and Chromodoris coi show attachments with sensory fields of different shape, length and grooving. When Chromodoris coi almost the entire rod with spiral grooves is occupied, in the Canthodoris pilosa only the upper part. Furthermore, inter alia even fields in brush shape, spring shape, documented with longitudinal wrinkles, and at the end of the rod fanning fields. Brushes, pens, trays are geometric shapes with large surface in a small space.
In addition to screw with pure rod antennas, there are snails ( Sternschnecke Born Ella stellifer ) in which the antennas are no headdresses, but to derive branching tentacles.
Etymology
The rhinophores name derives from its function from the olfactory organ. " Rhino " comes from the ancient Greek word ῥίς ( rhis ) for nose. " Phore " is derived from the ( New Latin ) " chromophores " for carry, and from the Greek word φορος ( phoros ), which means supporting.