Fish physiology is a scientific study of how parts of fish components work together in live fish. This can be contrasted with fish anatomy, which is the study of the shape or morphology of fish. In practice, fish and physiology anatomy complement each other, first dealing with fish structures, organs or component parts and how they are put together, as might be observed on the surgical table or under a microscope, and then dealing with how the components work together in live fish.
Video Fish physiology
Respiration
Most gas exchange fish use gills on both sides of the pharynx (throat). Gills is a network of threadlike structures called filaments. This filament has many functions and is involved in ionic and water transfer as well as the exchange of oxygen, carbon dioxide, acids and ammonia.Each filament contains capillary tissue which provides a large surface area for the exchange of oxygen and carbon dioxide.Gas exchange fish by attracting rich water oxygen through their mouths and pump them over their gills.In some fish, the capillary blood flow in the opposite direction to the water, causing the opposite exchange, gills push the oxygen-poor water out through the hole on the sides of the pharynx.
Fish from different groups can live out of water for a long time. Amphibian fish like mudskipper can live and move on land for a few days, or live in stagnant water or run out of oxygen. Many such fish can breathe air through various mechanisms. Anguillid eel skin can absorb oxygen directly. Electric buccal cavity eel can breathe air. Catfish from the Loricariidae family, Callichthyidae, and Scoloplacidae absorb the air through their digestive tract. Lungfish, with the exception of Australian lungfish, and bichir have lung pairs that are similar to tetrapods and should appear to swallow fresh air through the mouth and secrete air released through the gills. Garin and bowfin have bladder swimming with vascularization that works in the same way. Loaches, trahiras, and many catfish breathe by passing air through the intestine. Mudskippers breathe by absorbing oxygen in the skin (similar to frogs). A number of fish have evolved so-called accessory breathing organs that extract oxygen from the air. Labyrinth fish (like gouramis and bettas) have labyrinth organs over gills that perform this function. Some other fish have structures resembling labyrinth organs in form and function, especially snakehead, pikeheads, and the family of catfish Clariidae.
Air respiration is mainly used for fish that inhabit the shallow waters of seasonal variables where water oxygen concentrations can decrease seasonally. Fish depend only on dissolved oxygen, such as tengger and cichlids, rapidly suffocating, while air-breath lasts longer, in some cases in water that is little more than wet mud. At the most extreme, some air-breathing fish can survive in a moist burrow for weeks without water, entering aestivation state until the water returns.
Air breathing fish can be divided into mandatory air breath and facultative breath air. Remnants of compulsory air, such as African lungfish, are required to breathe air regularly or they suffocate. Facultative air respirators, such as catfish Hypostomus plecostomus , only breathe the air if they need to and can instead rely on their gills for oxygen. Much of the air breath is a facultative air breath that avoids energetic costs rising to the surface and exposure of fitness exposure surfaces.
All basal vertebrates breathe with gills. The gills are brought right behind the head, limiting the posterior margin of a series of openings from the esophagus to the outside. Each gill is supported by cartilage gill arch or bone. Vertebrate gills usually develop in the pharyngeal wall, along a series of gill openings to the outside. Most species use a counter-exchange system to increase the diffusion of substances inside and outside the gills, with blood and water flowing in opposite directions.
These gills consist of comb-like filaments, lamellae gills, which help increase the surface area for oxygen exchange. When the fish breathes, it pulls in its mouth full of water regularly. Then he pulled both sides of his throat together, forcing the water through the opening of the gills, so that it passed through the gills outward. The bony fish has three pairs of arches, the cartiline fish has five to seven pairs, while the primitive fish without jaws has seven pairs. The vertebrate ancestor no doubt has more arches, as some of his relatives have more than 50 pairs of gills.
High vertebrates do not develop gills, gill arch forms during fetal development, and laid the foundations of important structures such as the jaw, thyroid gland, larynx, columella (corresponding to stapes in mammals) and in malleus and incus mammals. Fish gill slits may be the evolutionary ancestors of the tonsils, thymus glands, and Eustachian tubes, as well as many other structures that originate from the embryonic branchial pouch.
Scientists have been investigating which parts of the body are responsible for keeping the respiratory rhythm. They found that neurons located in the brainstem were responsible for the origin of the respiratory rhythm. The positions of these neurons differ slightly from the centers of respiratory genesis in mammals but they lie in the same brain compartment, which has led to a debate about the homology of respiratory centers between aquatic and terrestrial species. In aquatic and terrestrial respiration, the exact mechanism by which neurons can produce this involuntary rhythm is not fully understood (see involuntary respiratory control).
Another important feature of the respiratory rhythm is that it is modulated to adapt to the body's oxygen consumption. As observed in mammals, fish "breathe" faster and heavier when they do physical exercise. The mechanism by which these changes occur has been strongly debated for over 100 years among scientists. The authors can be classified into 2 schools:
- Those who think that the main part of respiratory changes are pre-programmed in the brain, which would imply that neurons from the brain's drive center are connected to the respiratory center in anticipation of movement.
- Those who think that the main part of respiratory changes result from muscle contraction detection, and respiration that is adapted as a consequence of muscle contraction and oxygen consumption. This would imply that the brain has some sort of detection mechanism that will trigger a respiratory response when muscle contraction occurs.
Many now agree that both mechanisms may be present and complementary, or work together mechanisms that can detect oxygen and/or blood saturation of carbon dioxide.
bony fish
In bony fish, the gill is located in the branchial space covered by the bone operculum. The majority of species of bony fish have five pairs of gills, though some have lost some during evolution. The operculum can be important in adjusting the water pressure within the pharynx to allow proper gill ventilation, so the bony fish does not have to rely on the ram ventilation (and hence near constant movement) to breathe. The valve in the mouth keeps the water out.
Gill arches of bony fish usually do not have a septum, so the project's own gills from the arch, supported by individual gill rays. Some species maintain gill filters. Although all but the most primitive boned fish have no spiracles, the associated pseudobranch often remains, located at the base of the operculum. This, however, is often greatly reduced, consisting of a small number of cells without structures like the remaining gills.
Marine teleost also uses gills to remove electrolytes. Large gill surface area tends to create problems for fish trying to regulate the osmolarity of their internal fluids. Saltwater is less dilute than this internal fluid, so the marine fish lose a lot of water osmotically through its gills. To get back the water, they drank a large amount of sea water and took salt out. However, fresh water is thinner than the fish's internal fluid, so freshwater fish get the water osmotically through its gills.
In some primitive bony fish and amphibians, the larvae bear an external gill, branched from the gill arch. This is reduced in adulthood, their function is taken over by the gills right in fish and lungs in most amphibians. Some amphibians maintain the external larval gill in adulthood, the complex internal gill system as seen in fish appears to be lost forever in the early evolution of tetrapods.
Cartiline Fish
Like other fish, sharks extract oxygen from seawater when it passes through its gills. Unlike other fish, the gill slip of the shark is not covered, but lying on the back of the head. The modified slit called spiracle lies just behind the eye, which helps sharks by taking water during respiration and plays a major role in the sharks that live below. Spiracel decreases or disappears on active pelagic sharks. While sharks move, water passes through the mouth and above the gills in a process known as "ventilation ram". At rest, most sharks pump water above the gills to ensure a constant supply of oxygen water. A small number of species have lost the ability to pump water through their gills and have to swim without rest. These species are the obligatory ventilator and may suffocate if they can not move. Suitable ventilation of the ram also applies to some species of pelagic fish bony fish.
The process of respiration and circulation begins when deoxygenated blood leads to the heart of the two-space shark. Here the shark pumps blood into its gills through the ventral aortic artery where it branches into an afferent brachial artery. Reoxygenation occurs in the gills and the deoxygenated blood stream to the efferent brachial artery, which combines to form the dorsal aorta. Blood flows from the dorsal aorta throughout the body. Deoxygenated blood from the body then flows through the posterior cardinal vein and enters the posterior cardinal sinus. From there the blood enters the heart's ventricle and the cycle repeats itself.
Sharks and rays usually have five pairs of gill slits that open directly to the outside of the body, although some more primitive sharks have six or seven pairs. The adjacent cracks are separated by the gill arches of the ribs from which the long-term piece of the septum project is, partially supported by a further piece of cartilage called gill rays . Individual gill Lamellae is located on both sides of the septum. The base of the arch can also support the gill rib, a small projection element that helps filter food from water.
The smaller opening, the spiracle, is located behind the first gill slit. It contains a bit of pseudobranch that resembles gills in the structure, but only receives oxygenated blood by the correct gills. Spiracles are considered homologous by opening the ears in higher vertebrates.
Most sharks rely on ram vents, forcing water into the mouth and through the gills by swiming forward quickly. In slow-moving or under-lived species, especially between roller-skates and rays, spiracles can be enlarged, and fish breathe by sucking water through this hole, not through the mouth.
Chimaeras differ from other cartilagenous fish, losing both spiracles and the fifth gill slits. The rest of the gap is covered by the operculum, developed from the gill arch septum in front of the first gills.
Lamps and hagfish
Lamprey and hagfish do not have such gill slits. Instead, the gills are contained in a round bag, with a circular opening outward. Like the higher gills of the fish, each bag contains two gills. In some cases, openings can be combined together, effectively forming the operculum. Lamprey has seven pairs of bags, while hagfishe may have six to fourteen, depending on the species. In hagfish, the pouch is connected internally with pharynx. In adult lamprey, separate respiratory tubes develop under the proper pharynx, separating food and water from respiration by closing the valve at its anterior end.
Maps Fish physiology
Circulation
The circulatory system of all vertebrates is closed , just like in humans. However, fish, amphibian, reptile, and bird systems show the various stages of the evolution of the circulatory system. In fish, the system has only one circuit, with blood pumped through the gill capillaries and into the capillaries of body tissues. This is known as circulation one cycle . The fish's heart is therefore only a single pump (consisting of two rooms). Fish has a closed-loop circulation system. The heart pumps blood in a circle throughout the body. In most fish, the heart consists of four parts, including two rooms and the entrance and exit. The first part is the sinus venosus, a thin-walled sac that collects blood from the fish's veins before allowing it to flow into the second part, the atrium, which is a large muscle space. The atrium serves as a one-way front space, sending blood to the third, ventricle. The ventricle is a muscular space that has thick walls and pumps blood, first to the fourth part, bulbus arteriosus, large tube, and then out of the heart. The bulbus arteriosus is connected to the aorta, where blood flows into the gills for oxygenation.
In amphibians and most reptiles, a double circulation system is used, but the heart is not always completely separated into two pumps. Amphibians have three heart chambers.
Digestion
Jaws allow fish to eat a wide variety of foods, including plants and other organisms. Fish digests food through the mouth and breaks it down in the esophagus. In the stomach, food is more digested and, in many fish, is processed in a finger-shaped sac called caeca pylorus, which secretes digestive enzymes and absorbs nutrients. Organs like the liver and pancreas add enzymes and various chemicals as food travels through the digestive tract. The gut completes the process of digestion and absorption of nutrients.
In most vertebrates, digestion is a four-stage process involving the main structure of the gastrointestinal tract, starting with swallowing, placing food into the mouth, and ending with excretion of the digested material through the anus. From the mouth, food moves into the stomach, where the bolus is chemically broken. It then moves to the intestine, where the process of breaking food into simple molecules continues and the results are absorbed as nutrients into the circulatory and lymphatic system.
Although the exact shape and size of the abdomen vary widely among different vertebrates, the relative position of the esophageal and duodenal openings remains relatively constant. As a result, the organs always arc a little to the left before arching the back to meet the pyloric sphincter. However, lamprey, hagfish, chimaeras, lungfishes, and some teleost fish have no stomach at all, with the esophagus opening directly into the intestine. These animals all consume foods that require little food storage, or no pre-digestion with stomach juice, or both.
The small intestine is part of the gastrointestinal tract following the stomach and is followed by the colon, and where much of the digestion and absorption of food takes place. In fish, small bowel division is unclear, and the term anterior or proximal intestin may be used in lieu of duodenum. Small intestine is found in all teleosts, although the shape and length vary greatly between species. In teleosts, it is relatively short, usually about one and a half times the length of the fish's body. It usually has a number of pylorus caeca, a pocket-like structure along its length that helps to increase the overall surface area of ​​the organ to digest food. There is no ileocaecal valve in teleosts, with borders between the small intestine and rectum marked only by the end of the digestive epithelium.
No small intestine like non-teleost fish, such as shark, sturgeon, and lungfish. Instead, the digestive part of the intestine forms the intestinal spiral , connecting the stomach to the rectum. In this type of intestine, the gut itself is relatively straight, but has long creases along the inner surface spirally, sometimes for tens of turns. This valve greatly improves both the surface area and the effective length of the intestine. The spiral gut layer is similar to the small intestine in teleosts and non-mammalian tetrapods. In lamprey, the spiral valve is very small, probably because their diet needs a bit of digestion. Hagfish has no spiral valve at all, with digestion occurring almost throughout the length of the intestine, which is not divided into several regions.
The large intestine is the last part of the digestive system commonly found in vertebrate animals. Its function is to absorb water from food scraps that can not be digested, and then skip waste materials that are not useful from the body. In fish, there is no correct large intestine, but only a short rectum connecting the end of the digestive portion of the intestine to the cloaca. In sharks, these include the rectum glands that secrete salt to help the animals maintain an osmotic balance with sea water. The glands resemble the cecum in the structure, but not the homologous structure.
Like many aquatic animals, most fish release their nitrogenous waste as ammonia. Some waste spread through the gills. The blood waste is filtered by the kidneys.
Saltwater fish tend to lose water because of osmosis. Their kidneys return water to the body. The opposite is true of freshwater fish: they tend to get water osmotically. Their kidneys produce dilute urine for excretion. Some fish have specifically adapted the varying kidney function, allowing them to move from fresh water to saltwater.
On sharks, digestion can take a long time. Food moves from mouth to stomach in the shape of J, where it is stored and the initial digestion occurs. Unwanted items will never get past the stomach, and instead the shark also vomits or flips its stomach out and removes unwanted items from its mouth. One of the biggest differences between shark and mammalian digestive systems is that sharks have shorter intestines. This short length is achieved by a spiral valve with multiple turns in one short section rather than a long tube-like tube. The valve provides a long surface area, requiring food to circulate in the short intestine until fully digested, when the waste product residue enters the cloaca.
Endocrine system
Oxytocin is a group of neuropeptides found in most vertebrates. One form of oxytocin function as a hormone associated with human love. In 2012, researchers injected cichlid from the social species of Neolamprologus pulcher, either with isotocin or with saline control. They found isotocin to increase the "response to social information", suggesting "it is the main regulator of social behavior that has evolved and survived since ancient times".
Pollution Effects
Fish can accumulate pollutants that are discharged into waterways. The estrogenic compounds found in pesticides, contraceptives, plastics, plants, fungi, bacteria, and synthetic drugs that are crushed into the river affect the endocrine system of native species. In Boulder, Colorado, white suckers found in downstream municipal wastewater treatment plants show abnormal sexual interruptions or development. Fish have been exposed to higher estrogen levels, and lead to feminine fish. Men display female reproductive organs, and both sexes have reduced fertility, and higher mortality hatch. The same feminization effect can also be seen in African frogs when exposed to high levels of atrazine, widely used pesticides. In marine ecosystems, organochlorine contaminants such as pesticides, herbicides (DDT), and chlordans accumulate in fish tissues and disrupt their endocrine systems. The high frequency of infertility and high levels of organochlorine have been found in bonnethead sharks along the Gulf Coast of Florida. These endocrine disrupting compounds have structures similar to the natural hormones in fish. They can modulate hormonal interactions in fish by:
- binds cell receptors, causing unexpected and abnormal cell activity
- block receptor sites, block activity
- promote the creation of extra receptor sites, amplify the effects of hormones or compounds
- interacts with hormones that occur naturally, change their shape and effects
- affect the synthesis of hormones or metabolism, causing improper balance or quantity of hormones
Osmoregulation
The two main types of osmoregulation are osmoconformer and osmoregulator. Osmoconformers match their body osmolarity with their active or passive environment. Most marine invertebrates are osmoconformers, although their ionic composition may differ from sea water.
Osmoregulators strictly regulate the osmolarity of their bodies, which always remain constant, and more common in the animal kingdom. Osmoregulator actively controls salt concentration even though the concentration of salt in the environment. An example is freshwater fish. Active gills take salt from the environment by using mitochondrial rich cells. The water will diffuse into the fish, thus releasing the urine highly hypotonic (dilute) to expel all the excess water. A sea fish has an internal osmotic concentration lower than the surrounding seawater, so it tends to lose water and get salt. Actively remove salt from gills. Most fish are stenohaline, which means they are limited to salt or fresh water and can not survive in water with different salt concentrations than those adapted. However, some fish exhibit a remarkable ability to effectively osmoregulate in various salinity; fish with this ability are known as euryhaline species, for example, salmon. Salmon has been observed to inhabit two very different environments - the ocean and freshwater - and it is inherent to adapt to both by bringing behavioral and physiological modifications.
In contrast to bony fish, with the exception of coelacanth, blood and shark tissue and other Chondrichthyes are generally isotonic to their marine environment due to the high concentrations of urea and trimethylamine N-oxide (TMAO), which allows them to be in osmotic equilibrium with sea water. This adaptation prevents most sharks from surviving in fresh water, and therefore they are confined to the marine environment. There are some exceptions, such as the bull shark, which has developed a way to alter its kidney function to remove large amounts of urea. When the shark dies, urea is broken down into ammonia by bacteria, causing the body to die to gradually smell the ammonia.
Sharks have adopted different and efficient mechanisms to conserve water, ie, osmoregulation. They maintain urea in their blood in relatively higher concentrations. Urea destroys live tissue so, to overcome this problem, some fish retain trimethylamine oxide . This provides a better solution for urea toxicity. Sharks, have slightly higher solute concentrations (ie above 1000 mOsm which is the concentration of dissolved sea), do not drink water like freshwater fish.
Thermoregulation
Homeothermy and poikilothermy refer to how stable the temperature of an organism is. Most endothermic organisms are homeothermic, such as mammals. However, animals with facultative endomymy are often poikilothermic, meaning their temperatures may vary. Similarly, most fish are ectotherms, because all their heat comes from the surrounding water. However, most are homeotherms because the temperature is very stable.
Most organisms have a preferred temperature range, but some can adapt to cooler or warmer temperatures than they normally use. The preferred temperature of the organism is usually the temperature at which the physiological processes of the organism can act at an optimal level. When fish become accustomed to other temperatures, the efficiency of their physiological processes may decrease but will continue to function. This is called a thermal neutral zone in which an organism can survive indefinitely.
H.M. Vernon has done the work at the temperature of death and the temperature of paralysis (heat stiffness temperature) of various animals. He found that species of the same class showed very similar temperature values, of which Amphibia examined was 38.5 ° C, fish 39 ° C, Reptile 45 ° C, and various Mollusks 46 ° C.
To cope with low temperatures, some fish have developed the ability to keep functioning even when water temperatures are below freezing; some use antifreeze or natural antifreeze proteins to resist the formation of ice crystals in their tissues.
Most sharks are "cold-blooded" or, more precisely, poikilotermik, meaning that their inner body temperature corresponds to their ambient environment. Lamnidae family members (such as short-tailed sharks and large white sharks) are homeothermic and maintain a higher body temperature than the surrounding water. In this shark, an aerobic red muscle strip located near the center of the body generates heat, which the body stores through a reverse exchange mechanism by a vascular system called rete mirabile ("miraculous net"). Common destroyer sharks have the same mechanisms to maintain a high body temperature, which is considered to have evolved independently.
Tuna can maintain the temperature of certain parts of their bodies above the ambient sea water temperature. For example, bluefin tuna maintains a core body temperature of 25-33 ° C (77-91 ° F), in water as cold as 6 ° C (43 ° F). However, unlike typical endothermic creatures such as mammals and birds, tuna does not maintain the temperature in a relatively narrow range. Tuna reaches endothermy by saving the heat generated through normal metabolism. The rete mirabile ("beautiful clean"), arterial blood vessels and arteries at the periphery of the body, transfers heat from venous blood to arterial blood through the current counter-exchange system, thereby reducing the effects of surface cooling. This allows tuna to increase the temperature of a very aerobic network of skeletal muscles, eyes and brain, which supports faster swimming speeds and reduced energy expenditure, and which allows them to survive in cooler waters in a wider range of marine environments than any other fish. However, in all tuna, the heart operates at ambient temperature, as it receives the cooled blood, and direct coronary circulation of the gills.
- Homeothermy: Although most fish are exclusively ectothermic, there are exceptions. Specific fish species maintain high body temperature. Endothermic teleosts (bony fish) are all located in the Scombroidei suborder and include billfishes, tuna, including the primitive "mackerel species", Gasterochisma melampus . All sharks in the Lamnidae family - makmo shortfin, long mako, white, porbeagle, and shark salmon - are endothermic, and evidence suggests that trait exists in the Alopiidae family (shark thresher). The degree of endothermy varies from billfish, which only warms their eyes and brains, to bluefin tuna and porbeagle sharks that keep body temperature rising by more than 20 ° C above ambient water temperature. See also gigantothermy . Endothermy, though metabolically expensive, is thought to provide benefits such as increased muscle strength, higher central nervous system processing, and higher levels of digestion.
In some fish, the rete mirabile allows an increase in muscle temperature in the area where these veins and arteries are found. This fish is able to thermoregulate certain areas of the body. In addition, this increase in temperature causes an increase in basal metabolic temperature. Fish can now break ATP at a higher level and ultimately can swim faster.
Swordfish eyes can produce heat to better detect their prey at a depth of 2000 feet.
Muscular system
Fish swim by contracting red muscles lengthwise and white muscles oriented at an angle. Red muscle is aerobic and requires oxygen supplied by myoglobin. White muscle is anaerobic and does not require oxygen. Red muscles are used for ongoing activities such as slow-moving sailing on marine migration. White muscles are used for bursts of activity, such as jumping jumps or sudden speeds to catch prey.
Most fish have white muscle, but some fish muscles, such as scombroids and salmon, range from pink to dark red. The red myotomal muscles are derived from myoglobin, the oxygen-binding molecule, which tuna expresses in much higher quantities than most other fish. Oxygen-rich blood further enables the delivery of energy to their muscles.
Most fish move in turn contractions of a set of muscles on both sides of the spine. This contraction forms an S-shaped curve that moves down the body. When each curve reaches the rear fin, the reverse force is applied to the water, and together with the fins, moves the fish forward. The fish fins function like an airplane flap. The fins also increase the surface area of ​​the tail, increasing the speed. An efficient fish body reduces the amount of friction from water.
The typical characteristic of many animals that utilize motion movements is that they have segmented muscles, or blocks of myomeres, running from their heads to the tail separated by a connective tissue called myosepta. In addition, some muscle groups are segmented, such as lateral hypaxal muscles in a longitudinal oriented angle-oriented salamander. For these skewed oriented fibers, the strain in the elongated direction is greater than the strain in the direction of the muscle fibers leading to an architectural gear ratio greater than 1. The higher initial orientation angle and dorsoventral bulge result in faster muscle contraction but produce lower production amount of power. It is hypothesized that animals use a variable gearing mechanism that allows setting their own strength and speed to meet the mechanical demands of contraction. When the pennate muscle is subjected to low strength, resistance to changes in width of the muscle causes it to spin which consequently results in a higher architectural gear ratio (AGR) (high speed). However, when subjected to high strength, the fiber strength component perpendicularly overcomes resistance to changes in width and compresses the muscles resulting in a lower AGR (capable of maintaining higher output power).
Most fish bend as simple homogeneous rays during swimming through contraction of elongated red muscle fibers and tilted oriented white muscle fibers in the axial segmented muscle. The fiber tension (? F) experienced by longitudinal red muscle fibers is equivalent to the elongated strain (? X). The deeper muscle fibers of white muscle indicate diversity in settings. These fibers are arranged into a cone-shaped structure and attached to a connective tissue sheet known as myosepta; each fiber exhibits a typical dorsoventral (?) and mediolateral (?) trajectory. The theory of segmented architecture predicts that,? X & gt; ? f. This phenomenon results in an architectural gear ratio, defined as a longitudinal strain divided by a fiber strain (X X/F F), greater than one and longitudinal speed amplification; Furthermore, this emerging speed amplification can be supplemented by variable architectural equipment through mesolateral and dorsoventral shaping, a pattern seen in muscle contraction that signifies. The red-white gearing ratio (red? F/white? F) captures the combined effects of longitudinal red muscle fibers and tilted white muscle fibers.
Floating rate
The fish body is denser than water, so fish must balance the difference or they will sink. Many bony fish have internal organs called bladder swimming, or gas bladders, which adjust their buoyancy by gas manipulation. In this way, the fish can stay in the current water depth, or rise or fall without having to waste energy in swimming. The bladder is found only in bony fish. In more primitive groups such as small fish, bichir and lungfish, the bladder opens into the esophagus and doubles as the lungs. Often there are no fish that swim fast like tuna and mackerel families. The open bladder condition into the esophagus is called the physostome, a closed condition physoclist. In the latter, the gas content of the bladder is controlled through the rete mirabilis, a vascular tissue that affects the exchange of gas between the bladder and the blood.
In some fish, the rete mirabile fills the bladder swimming with oxygen. The opposite exchange system is used between venous capillaries and arteries. By lowering the pH level in the venous capillaries, oxygen breaks away from blood hemoglobin. This causes an increase in blood venous oxygen concentration, allowing oxygen to diffuse through the capillary membrane and into the artery capillaries, where oxygen is still sequestered to hemoglobin. The diffusion cycle continues until the oxygen concentration in the arterial capillaries is saturated (greater than the oxygen concentration in the swim bladder). At this point, the free oxygen in the arterial capillaries diffuses into the bladder swimming through the gas glands.
Unlike bony fish, sharks do not have a swimming bag containing gas for buoyancy. In contrast, sharks rely on a large heart filled with oil containing squalene, and their cartilage, which is roughly half the normal bone density. Their liver forms up to 30% of their total body mass. Liver effectiveness is limited, so sharks use dynamic lifting to maintain depth when not swimming. Tiger sand sharks store air in their stomachs, using it as a swim bladder form. Most sharks must constantly swim in order to breathe and can not sleep for long without drowning (if at all). However, certain species, such as shark nurses, are able to pump water in their gills, allowing them to rest on the ocean floor.
Sensory system
Most fish have highly developed sense organs. Almost all fish during the day have color vision that is at least as good as humans (see vision in fish). Many fish also have chemoreceptors responsible for their extraordinary sense of smell and smell. Although they have ears, many fish may not hear very well. Most fish have sensitive receptors that form a rib-line system, which detects soft currents and vibrations, and feels the movement of nearby fish and prey. Sharks can sense frequencies in the range of 25 to 50 Hz through the ribs.
Fish adjust to using landmarks and can use mental maps based on some landmarks or symbols. Fish behavior in the labyrinth reveals that they have spatial memory and visual discrimination.
Vision
Vision is an important sensory system for most fish species. Fish eyes are similar to terrestrial vertebrates like birds and mammals, but have more rounded lenses. Their retinas generally have stem cells and cone cells (for skotopic and photopic vision), and most species have color vision. Some fish can see ultraviolet and some can see polarized light. Among the jawless fish, lampreys have well-developed eyes, while hagfish only has primitive eyespots. The vision of the fish shows adaptation to their visual environment, for example deep-sea fish have eyes that match the dark environment.
Hearing
Hearing is an important sensory system for most species of fish. The auditory threshold and the ability to localize the sound source are reduced underwater, where the speed of sound is faster than in the air. Underwater hearing is done by bone conduction, and the localization of sound seems to depend on the difference in amplitude detected by bone conduction. Aquatic animals such as fish, however, have more specialized specialized hearing aids under water.
Fish can sense sound through their lateral lines and otolith (ears). Some fish, such as some goldfish and herring species, hear through their swimming sacs, which function more like hearing aids.
Hearing develops well in goldfish, which has Weberian organs, three special vertebral processes that transfer vibrations in the bladder to swim to the inner ear.
Although it is difficult to test the hearing of sharks, they may have sharp hearing and may be able to hear prey for miles and miles. Small opening on each side of their head (not spiracle) leads directly to the inner ear through a thin channel. The ribs show the same arrangement, and are open to the environment through a series of openings called rib pores. This is a general reminder of the origin of two vibration and noise detecting organs grouped together as an acoustico-lateral system. In bony fish and external opening tetrapod to the inner ear has been lost.
Chemoreception
Sharks have a keen sense of smell, located in short (united, unlike bone fish) channels between the anterior and posterior nostrils, with some species capable of detecting at least one part per million of blood in seawater.
The shark has the ability to determine the direction of the scent given based on the time of aroma detection in each nostril. This is similar to the mammal method used to determine the direction of sound.
They are more interested in the chemicals found in the intestines of many species, and as a result often linger near or at waste disposal. Some species, such as nurse sharks, have external spines that greatly increase their ability to feel prey.
Magnetoception
Electroreception
Some fish, such as catfish and sharks, have organs that detect weak electrical currents at the millivolt order. Other fish, such as South American electric fish, Gymnotiformes, can produce weak electrical currents, which they use in navigation and social communication. On the shark, Lorenzini's ampullae is an electoreceptor organ. The numbers are hundreds to thousands. The shark uses the Lorenzini ampullae to detect the electromagnetic fields generated by all living things. It helps sharks (especially hammerhead sharks) find their prey. Sharks have the greatest electrical sensitivity in any animal. The sharks find prey hidden in the sand by detecting the electric fields they produce. Ocean currents moving in the Earth's magnetic field also produce electric fields that sharks can use for orientation and navigation possibilities.
- Ampullae from Lorenzini allows sharks to feel the release of electricity.
- An electric fish can produce an electric field by modifying the muscles in its body.
Pain
Experiments conducted by William Tavolga provide evidence that fish have a response of pain and fear. For example, in the Tavolga experiment, the toadfish grunted when electrocuted and over time they grunted just by looking at the electrodes.
In 2003, Scottish scientists at the University of Edinburgh and Roslin Institute concluded that the behavior of rainbow trout is often associated with pain in other animals. Bee venom and acetic acid injected into the lips cause the fish to shake their bodies and rub their lips along the sides and floors of their tank, which the researchers conclude is an attempt to relieve pain, similar to what mammals do. Neurons are fired in patterns that resemble human neuronal patterns.
Professor James D. Rose of the University of Wyoming claims the study is flawed because it does not provide evidence that fish have "consciousness, especially a kind of meaningful consciousness like us". Rose argues that because the brains of fish are so different from the human brain, the fish may not be aware of the human way, so a reaction similar to that of a human reaction to pain has another cause. Rose has published a study a year earlier on the grounds that fish can not feel pain because their brains lack the neocortex. However, animal behavioralist Temple Grandin argues that fish can still have consciousness without the neocortex because "different species can use different structures and brain systems to handle the same function."
Animal welfare supporters raise concerns about possible fish suffering caused by fishing. Some countries, like Germany have banned certain types of fish, and the British RSPCA now officially prosecute cruel people against fish.
The reproduction process
Development of Oogonia in teleosts fish varies according to the group, and the determination of the dynamics of oogenesis allows understanding of the process of maturation and fertilization. Changes in the nucleus, ooplasm, and surrounding layers characterize the process of oocyte maturation.
Postovulation follicles are structures that form after oocyte release; they have no endocrine function, present a wide irregular lumen, and are rapidly reabsorbed in a process involving follicular cell apoptosis. A degenerative process called follicular atresia reabsorbs vitellogenic oocytes that do not spawn. This process can also occur, but more rarely, in oocytes at other developmental stages.
Some fish are hermaphrodites, have both testes and ovaries either at different phases in their life cycle or, as in the hamlet, have them simultaneously.
More than 97% of all known fish are vegetated, that is, eggs develop outside the mother's body. Examples of ovipar fish include salmon, goldfish, cichlid, tuna, and eel. In most of these species, fertilization occurs outside the mother's body, with male and female fish dumping the gametes into the surrounding water. However, some oviparous fish perform internal fertilization, with men using a kind of intromittent organ to deliver sperm into the female genital opening, especially oviparous sharks, such as horn sharks, and colored rays, such as roller skates. In this case, males are equipped with a pair of modified pelvic fins known as claspers.
Sea fish can produce large amounts of eggs that are often released into open water columns. Eggs have an average diameter of 1 millimeter (0.039 inches). Eggs are generally surrounded by extraembryonic membranes but do not develop hard or soft shells around this membrane. Some fish have thick and coarse coats, especially if they have to withstand physical strength or drought. Eggs of this type can also be very small and fragile.
Newly hatched ovipar fish are called larvae. They are usually poorly formed, carrying large yolk sacs (for food) and very different in appearance from teen and adult specimens. The larval period in oviparous fish is relatively short (usually only a few weeks), and the larvae quickly grow and alter appearance and structure (a process called metamorphosis) to become adolescents. During this transition period larvae have to shift from their yolk sac to feed on zooplankton prey, a process that relies on usually inadequate zooplankton density, starvation of many larvae.
In ovoviviparous eggs the egg develops within the mother's body after internal fertilization but receives little or no food directly from the mother, depending on the yolk. Each embryo develops in its own egg. Examples of known ovoviviparous fish include guppies, angel sharks, and coelacanths.
Some fish species are vivipar. In such species the mother preserves the egg and nourishes the embryo. Typically, viviparous fish have structures similar to the placenta seen in mammals that connect the mother's blood supply to the embryo. Examples of vivipar fish include surf-perches, splitfins, and lemon shark. Some viviparous fish exhibit oophagy, in which the developing embryo feeds on another egg produced by the mother. It has been observed mainly among sharks, such as mako shortfin and porbeagle, but is known for some bony fishes as well, such as halfbeak Nomorhamphus ebrardtii . Intrauterine cannibalism is a more unusual vivipary way, in which the largest embryo takes on a weaker and smaller brother. This behavior is also most commonly found among sharks, such as the gray nurse shark, but has also been reported for Nomorhamphus ebrardtii .
In many species of fish, fins have been modified to allow internal fertilization.
Aquarists generally refer to ovoviviparous and viviparous fish as livebearers.
- Many fish species are hermaphrodites. Synchronous Hermafrodit has both ovaries and testes at the same time. sequential hygodies have both types of tissue in their gonads, with one dominant species while the fish belonging to the appropriate gender.
Social behavior
Cognition
See also
References
Further reading
- Bernier NJ, Van Der Kraak G, Farrell AP and Brauner CJ (2009) Fish Physiology: Fish Neuroendocrinology Academic Press. ISBN: 978-0-08-087798-3.
- Eddy FB and Handy RD (2012) Ecology and Environmental Physiology of Fish Oxford University Press. ISBN 978-0-19-954095-2.
- Evans DH, JB Claiborne and S Currie (Eds) (2013) Physiology Fish 4th edition, CRC Press. ISBN: 978-1-4398-8030-2.
- Grosell M, Farrell AP and Brauner CJ (2010) Fish Physiology: Multifunctional Fish Intestines Academic Press. ISBN 978-0-08-096136-1.
- Hara TJ and Zielinski B (2006) Fish Physiology: Sensory System of Neuroscience Academic Press. ISBN 978-0-08-046961-4.
- Kapoor BG and Khanna B (2004) "Ichthyology handbook" Page 137-140, Springer. ISBN: 978-3-540-42854-1.
- McKenzie DJ, Farrell AP and Brauner CJ (2007) Physiology of Fish: Primitive Fish Academic Press. ISBN 978-0-08-054952-1.
- Slave Train, Wilson RW and Balshine S (2006) Fish Behavior and Physiology Gulf Professional Publishing. ISBN 978-0-12-350448-7.
- Wood CM, Farrell AP and Brauner CJ (2011) Fish Physiology: Non-Important Metal Homeostasis and Toxicology Academic Press. ISBN 978-0-12-378634-0.
External links
Source of the article : Wikipedia
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