How many Lateral lines (옆줄, 측선) does Kelp Greenling have?

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Lateral line


In this oblique view of a goldfish (Carrasius auratus), some of the pored scales of the lateral line system are visible.

The lateral line, also called lateral line system (LLS) or lateral line organ (LLO), is a system of senseorgans found in aquatic vertebrates, used to detect movement, vibration, and pressure gradients in the surrounding water.

The sensory ability is achieved via modified epithelial cells, known as hair cells, which respond to displacement caused by motion and transduce these signals into electrical impulses via excitatory synapses. Lateral lines serve an important role in schooling behavior, predation, and orientation. Fish can use their lateral line system to follow the vortices produced by fleeing prey. Lateral lines are usually visible as faint lines of pores running lengthwise down each side, from the vicinity of the gill covers to the base of the tail. In some species, the receptive organs of the lateral line have been modified to function as electroreceptors, which are organs used to detect electrical impulses, and as such, these systems remain closely linked. Most amphibian larvae and some fully aquatic adult amphibians possess mechanosensitive systems comparable to the lateral line.

Due to many overlapping functions and their great similarity in ultrastructure and development, the lateral line system and the inner ear of fish are often grouped together as the octavolateralis system (OLS).

Function



The small holes on the head of this Northern pike (Esox lucius) contain neuromasts of the lateral line system.

The lateral line system allows the detection of movement, vibration, and pressure gradients in the water surrounding an animal, providing spatial awareness and the ability to navigate in the environment. This plays an essential role in orientation, predatory behavior, defense, and social schooling.[3] A related aspect to social schooling is the hypothesis that schooling confuses the lateral line of predatory fishes. In summary, a single prey fish creates a rather simple acoustic pattern while pressure gradients of many closely swimming (schooling) prey fish will overlap; that creates a complex pattern, and accordingly the predator will be unable to identify the individual fish through lateral line perception.[4]
The lateral line system is necessary to detect vibrations made by prey, and to orient towards the source to begin predatory action.[5] Fish are able to detect movement, produced either by prey or a vibrating metal sphere, and orient themselves toward the source before proceeding to make a predatory strike at it. This behavior persists even in blinded fish, but is greatly diminished when lateral line function was inhibited by CoCl2 application. Cobalt chloride treatment results in the release of cobalt ions, disrupting ionic transport and preventing signal transduction in the lateral lines.[6] These behaviors are dependent specifically on mechanoreceptorslocated within the canals of the lateral line.[5]
The role mechanoreception plays in schooling behavior was demonstrated in a 1976 study. A school of Pollachius virens was established in a tank and individual fish were removed and subjected to different procedures before their ability to rejoin the school was observed. Fish that were experimentally blinded were able to reintegrate into the school, while fish with severed lateral lines were unable to reintegrate themselves. Therefore, reliance on functional mechanoreception, not vision, is essential for schooling behavior.[7] A study in 2014 suggests that the lateral line system plays an important role in the behavior of Mexican blind cave fish (Astyanax mexicanus).[8]

AnatomyEdit





Some scales of the lateral line (center) of a Rutilus rutilus.



A three-spined stickleback with stained neuromasts

The major unit of functionality of the lateral line is the neuromast. The neuromast is a mechanoreceptiveorgan which allows the sensing of mechanical changes in water. There are two main varieties of neuromasts located in animals, canal neuromasts and superficial or freestanding neuromasts. Superficial neuromasts are located externally on the surface of the body, while canal neuromasts are located along the lateral lines in subdermal, fluid filled canals. Each neuromast consists of receptive hair cells whose tips are covered by a flexible and jellylike cupula. Hair cells typically possess both glutamatergic afferent connections and cholinergicefferent connections.[9] The receptive hair cells are modified epithelial cells and typically possess bundles of 40-50 microvilli "hairs" which function as the mechanoreceptors.[10] These bundles are organized in rough "staircases" of hairs of increasing length order.[11] This use of mechanosensitive hairs is homologous to the functioning of hair cells in the auditory and vestibular systems, indicating a close link between these systems.[12]
Hair cells utilize a system of transduction that uses rate coding in order to transmit the directionality of a stimulus. Hair cells of the lateral line system produce a constant, tonic rate of firing. As mechanical motion is transmitted through water to the neuromast, the cupula bends and is displaced. Varying in magnitude with the strength of the stimulus, shearing movement and deflection of the hairs is produced, either toward the longest hair or away from it. This results in a shift in the cell's ionic permeability, resulting from changes to open ion channels caused by the deflection of the hairs. Deflection towards the longest hair results in depolarization of the hair cell, increased neurotransmitter release at the excitatory afferent synapse, and a higher rate of signal transduction. Deflection towards the shorter hair has the opposite effect, hyperpolarizing the hair cell and producing a decreased rate of neurotransmitter release.[12] These electrical impulses are then transmitted along afferent lateral neurons to the brain.
While both varieties of neuromasts utilize this method of transduction, the specialized organization of superficial and canal neuromasts allow them different mechanoreceptive capacities. Located at the surface of an animal's skin, superficial organs are exposed more directly to the external environment. Though these organs possess the standard "staircase" shaped hair bundles, overall the organization of the bundles within the organs is seemingly haphazard, incorporating various shapes and sizes of microvilli within bundles. This suggests a wide range of detection, potentially indicating a function of broad detection to determine the presence and magnitude of deflection caused by motion in the surrounding water.

In contrast, the structure of canal organs allow canal neuromasts to be organized into a network system that allows more sophisticated mechanoreception, such as the detection of pressure differentials. As current moves across the pores of a canal, a pressure differential is created over the pores. As pressure on one pore exceeds that of another pore, the differential pushes down on the canal and causes flow in the canal fluid. This moves the cupula of the hair cells in the canal, resulting in a directional deflection of the hairs corresponding to the direction of the flow.

This method allows the translation of pressure information into directional deflections which can be received and transduced by hair cells.

Electrophysiology

Notes

References

Last edited 4 months ago by an anonymous user

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