SENSORY ORGANS OF FISH

Jan 19, 2011 Lorenzo Martinez Bernal CURIOSITIES 12

 SENSORY ORGANS OF FISH

THE SENSORY ORGANS OF FISH

RESPIRATORY SYSTEM

Fish do most gas exchange by using gill, They found on both sides of the pharynx. The gills are made of threadlike structures called gill filaments. Each of these filaments contain capillaries, They are allowing a large surface area for the exchange of oxygen and carbon dioxide. This exchange occurs when the pez draws water, It is passing through the gills.

there are fish, like sharks and lampreys, having multiple openings gill. Nevertheless, Most fish have gills protected by a bony cover called operculum.

Being able to breathe air is directly a result of adaptation to fish that inhabit shallow water, where levels vary or where the concentration of oxygen in water may decrease in certain seasons. The mechanisms for this are varied. The thin skin of electric eels allow them a degree of absorption of oxygen. They can also swallow breathing air directly from the surface. catfishes of the families Loricariidae, Callichthyidae and Scoloplacidae are able to absorb air through your digestive tract.

For lungfish and poliptéridos described lungs similar to tetrapods, so they must rise to the surface of the water to swallow fresh air through the mouth to be passed through the gills.

DIGESTIVE SYSTEM

While all species of fish have mouths, All jaws have not developed (example is agnathans). In the case of species that if developed jaws, This allowed them to access a much wider variety of foods, including plants and other organisms.

In fish, food being ingested through the mouth, It is broken down in the stomach. Organs such as liver and pancreas added digestive enzymes. Nutrient uptake is via the intestine.

LOCOMOTOR SYSTEM

In order to move in the best way in the aquatic environment (mainly), fish have developed a series of fins, with different functions, some of them are:

dorsal fins: Located in the back area, its main function is to provide stability and maneuverability.

caudal fin:  Located in the queue, its function is to promote swimming.

anal fins: Located ventral to the anus, its function is stabilizing.

pectoral fins: Located behind the gills, its main function is stabilizing, although there are interesting modifications of these fins (as in the case Sailfish).

pelvic fins or ventrales:  Ventral to the pectoral fins.

CIRCULATORY SYSTEM

Fish have a closed circulatory system with a heart that pumps blood through a single circuit through the body. Blood from the heart to the gills, of these to the body, and finally returns to the heart. In most fish heart consists of four parts: venous sinus, the atrium, ventricle and bulbus arteriosus. Despite consist of four parts, the heart of the fish consists of two cavities located in series, an atrium and a ventricle. The sinus venosus is a thin-walled chamber that receives blood from the veins of the fish before allowing it to flow to the atrium, a large muscular chamber and serves as a unique address compartment which directs the blood into the ventricle. The ventricle bag is a thick-walled muscular pumping charge to the heart. The ventricle contracts and pushes the blood to a large tube called arteriosus bulb. At the end of the opposite side, arteriosus bulb meets a large blood vessel called the aorta, through which blood flows into the gills of fish.

EXCRETORY SYSTEM

Like many aquatic animals, most of the fish excrete waste nitrogen as ammonia. Part of their excretions diffuse through the gills into the surrounding water. The rest is expelled by the kidneys, excretory organs that filter waste from the blood. Kidneys help fishes control the amount ammonia in their bodies. Saltwater fish tend to lose water because of osmosis. In saltwater fish, kidneys concentrate garbage and leave the body as much water as they possibly can. In the case of freshwater fish, the situation is reversed and water tend to get continuously. The kidneys of freshwater fish are specially adapted to pump large amounts of urine diluida.Algunos fish have developed specially adapted kidneys that change their function, allowing them to move from freshwater to seawater.

NERVOUS SYSTEM

Central Nervous System

Compared with other vertebrates, fish generally have a small brain in relation to body size, about one fifteenth of the cerebral mass bird or mammal of a size similar.Sin however, Some fish have a relatively large brain, such as the fish and sharks family Mormyridae, whose brains cerebral ratio and body mass similar to birds and marsupials.

The brain is divided into several regions. On the front are the olfactory lobes, a pair of structures that receive and process signals from the nares through two olfactory nerves. The olfactory lobes are more developed in fishes that hunt primarily by smell, as hagfish, sharks and catfish. After the telencephalon olfactory lobes or forebrain is, bilobular structure in fish smell particularly concerned.

Connecting the forebrain to the midbrain is the diencephalon (in the diagram adjacent, this structure is below the optic lobes and therefore not visible). Diencephalon performs various functions associated with hormones and homeostasis. The pineal gland is located just above the diencephalon. This structure performs many different functions, including light perception, maintaining heart rate and control of pigmentation changes.

The midbrain contains the two optical lobes. These lobes are larger in species that hunt with view, such as rainbow trout and cichlids.

The hindbrain is particularly involved in swimming and balance. The cerebellum is a structure monolobular usually large and usually more large brain part. Hagfish and lampreys have relatively small cerebella, but instead the elephant fish is highly developed and apparently related to its electrical capacity.

Myelencephalon the back of the brain. In addition to controlling the functions of some muscles and body organs, in bony fish also responsible for breathing and osmoregulation.

sensory system

Many fish have highly developed sensory organs. Almost all daytime fish have well-developed eyes perceive color at least as well as humans. Many fish also have specialized cells known as chemoreceptors that are responsible for the senses of taste and smell. Although they have ears in their heads, many fish do not perceive sounds good. Nevertheless, fish most sensitive receptors that form the lateral line. The lateral line allows many fish detect gentle currents and vibrations, and feel the movement of their prey or other nearby fish. Some fishes, as sharks or puffers, bodies have perceived low electrical current. Others, as the electric eel, you can produce your own electricity.

Fish are oriented using benchmarks and may use mental maps of geometric relationships based on multiple signs or symbols. In studies with fish in labyrinths, It has been determined routinely used fish spatial memory and visual discrimination.

Ability to feel pain

Experiments conducted by Dr.. William Tavolga, zoólogo del Mote Marine Laboratory, provide evidence that fish show pain and fear responses. For example, in experiments Tavolga, toad fish snarling when he was subjected to electric shocks, and eventually they found that and snarling at the mere sight of an electrode.

In 2003, Scottish scientists at the University of Edinburgh who performed an investigation steelhead concluded that fish exhibit behaviors usually associated with pain. In tests at both the University of Edinburgh and the Roslin Institute, bee venom and acetic acid was injected into the lips of rainbow trout, what made the fish will balance their bodies and rubbed her lips against the walls and floor of their tanks, so the researchers believe were efforts to relieve pain, similarly to how they would mammals. Neurons in brains of fish showed similar to humans when they experience pain model.

Professor James D. Rose of the University of Wyoming criticized the study, stating that it was wrong, mainly because it did not provide evidence that fish have «conscious awareness, in particular a type of perception seems significantly to our». Rose argues that since the brain of the fish is very different from ours, fish are probably unaware (in the way that people are), so that similar reactions to human reactions to pain have other causes. Rose had published his own opinion a year earlier arguing that fish can not feel pain because their brains lack neocortex. Nevertheless, animal behaviorist Temple Grandin argues that the fish could have consciousness yet neocortex, why «different species and different systems can be used to treat brain structures the same functions.»

Advocates of animal rights expressed concerns about the possible suffering of fish caused by angling. In view of recent research, Some countries like Germany have banned certain types of fishing, y la Royal Society for the Prevention of Cruelty to Animals (RSPCA) British, it believes that the fish are unlikely to perceive pain in the same way that people, but currently there is evidence indicating that fish actually have the ability to perceive pain and suffering, so judicially persecuted individuals who are cruel to fish.

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