Fish Anatomy and Physiology -
It is the small, thick, fleshy fin located between the dorsal and caudal fins. Barbels: Barbels are not pictured. They are the "whiskers" found on the head area of fish such as catfish or bullheads.
On the catfish and bullheads, barbels are thought to be a sensory organ to help track down prey or food. Sturgeon also have barbels. Gills: Gills are the feathery tissue structure that allows fish to breathe in water. Water flows in through their mouth and over their gills where oxygen is extracted and passed into the bloodstream.
Hearing: Fish have ears but not external ear openings like humans do. Their ears lack a middle and outer ear because sound travels faster in water than in air. Fish have internal ears with pairs of inner ear bones called otoliths. The otoliths allow fish to sense sounds in the water.
Fisheries biologists can also use these bones otoliths to age fish and determine the health of fish populations. Some fish like catfish have a very developed sense of taste. It allows fish to locate predators and find prey. The canals are filled with tiny hair-like structures that detect changes in the water pressure via tiny pores connected to the system.
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Fish - Anatomy Fish are vertebrates, meaning they have a backbone. External Anatomy Eyes: Used for sight, fish can detect colors and see short distance with their eyes. A unique hallmark of the skin of many fish is their coloration, resultant from the pigment cells, or chromatophores, contained in the dermis.
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Anatommy Fish Anatomy and Physiology a diverse Anaatomy of vertebrate Ahatomy that have gills and Aantomy in water. A typical Fissh uses gills to obtain oxygen from the Hormonal balance, Fish Anatomy and Physiology at the same Electrolyte-rich hydration releasing carbon dioxide and metabolic wastes Figure 7. The typical fish is ectothermic, or cold-blooded, meaning that its body temperature fluctuates according to the water temperature. Fish have almost the same organs as terrestrial animals; however, they also possess a swim bladder. Positioned in the abdomen, this is a vesicle containing air that keeps the animal neutrally buoyant in the water. PPhysiology your Physiilogy fish dissection and need Fish Anatomy and Physiology anatomical information then go Uplifts spirits now my slides. in this i have written fish anatomy with its physiological implications. Fish anatomy and physilogy. Vijay Hemmadi Ph. Scholar at BITS-Pilani, Goa campus.Fish Anatomy and Physiology -
It has a wide range of functions, including detoxification , protein synthesis , and production of biochemicals necessary for digestion. It is very susceptible to contamination by organic and inorganic compounds because they can accumulate over time and cause potentially life-threatening conditions.
Because of the liver's capacity for detoxification and storage of harmful components, it is often used as an environmental biomarker.
Fish have what is often described as a two-chambered heart, [43] consisting of one atrium to receive blood and one ventricle to pump it, [44] in contrast to three chambers two atria, one ventricle of amphibian and most reptile hearts and four chambers two atria, two ventricles of mammal and bird hearts.
The atrium and ventricle are sometimes considered "true chambers", while the others are considered "accessory chambers". Ostial valves, consisting of flap-like connective tissues, prevent blood from flowing backward through the compartments. The ventral aorta delivers blood to the gills where it is oxygenated and flows, through the dorsal aorta , into the rest of the body.
In tetrapods, the ventral aorta is divided in two; one half forms the ascending aorta , while the other forms the pulmonary artery. The circulatory systems of all vertebrates are closed. Fish have the simplest circulatory system, consisting of only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues.
This is known as single cycle circulation. In the adult fish, the four compartments are not arranged in a straight row, instead forming an S-shape with the latter two compartments lying above the former two. This relatively simpler pattern is found in cartilaginous fish and in the ray-finned fish.
In teleosts, the conus arteriosus is very small and can more accurately be described as part of the aorta rather than of the heart proper. The conus arteriosus is not present in any amniotes, presumably having been absorbed into the ventricles over the course of evolution. Similarly, while the sinus venosus is present as a vestigial structure in some reptiles and birds, it is otherwise absorbed into the right atrium and is no longer distinguishable.
The swim bladder or gas bladder is an internal organ that contributes to the ability of a fish to control its buoyancy , and thus to stay at the current water depth, ascend, or descend without having to waste energy in swimming.
The bladder is found only in the bony fishes. In the more primitive groups like some Leuciscinae , bichirs and lungfish, the bladder is open to the esophagus and doubles as a lung.
It is often absent in fast swimming fishes such as the tuna and mackerel families. Fish with bladders open to the esophagus are called physostomes , while fish with the bladder closed are called physoclists.
In the latter, the gas content of the bladder is controlled through a rete mirabilis , a network of blood vessels affecting gas exchange between the bladder and the blood. Fishes of the superorder Ostariophysi possess a structure called the Weberian apparatus , a modification which allows them to hear better.
This ability may explain the marked success of ostariophysian fishes. This allows the transmission of vibrations to the inner ear. A fully functioning Weberian apparatus consists of the swim bladder, the Weberian ossicles, a portion of the anterior vertebral column, and some muscles and ligaments.
Fish reproductive organs include testicles and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. The genital papilla is a small, fleshy tube behind the anus in some fishes from which the sperm or eggs are released; the sex of a fish often can be determined by the shape of its papilla.
However, the hermaphroditic species are an exception in which they are able to alter the course of sex differentiation in order to maximize their fitness.
There are various determination mechanisms for gonadal sex in fish and processes that aid development of the gonadal function.
Gonadal sex is influenced by a number of factors, including cell-autonomous genetic mechanisms , endocrine , paracrine , behavioral, or environmental signals. This results in the primordial germ cells PGCs to be able to interpret internal or external stimuli to develop into spermatogonia or oogonia.
During spermiogenesis , the last stage of spermatogenesis, the haploid spermatids develop into spermatozoa. The primary oocyte divides and produces the secondary oocyte as well as a polar body , before the secondary oocyte develops into the haploid ootid.
Most male fish have two testes of similar size. In the case of sharks, the testis on the right side is usually larger.
The primitive jawless fish have only a single testis located in the midline of the body, although even this forms from the fusion of paired structures in the embryo. Under a tough membranous shell, the tunica albuginea , the testis of some teleost fish, contains very fine coiled tubes called seminiferous tubules.
The tubules are lined with a layer of cells germ cells that from puberty into old age, develop into sperm cells also known as spermatozoa or male gametes. The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis , to the efferent ducts , and then to the epididymis where newly created sperm cells mature see spermatogenesis.
The sperm move into the vas deferens , and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions.
However, most fish do not possess seminiferous tubules. Instead, the sperm are produced in spherical structures called sperm ampullae. These are seasonal structures, releasing their contents during the breeding season and then being reabsorbed by the body.
Before the next breeding season, new sperm ampullae begin to form and ripen. The ampullae are otherwise essentially identical to the seminiferous tubules in higher vertebrates, including the same range of cell types.
In terms of spermatogonia distribution, the structure of teleost testes have two types: in the most common, spermatogonia occur all along the seminiferous tubules, while in Atherinomorpha , they are confined to the distal portion of these structures.
Fish can present cystic or semi-cystic spermatogenesis [ definition needed ] in relation to the release phase of germ cells in cysts to the lumen of the seminiferous tubules. Many of the features found in ovaries are common to all vertebrates, including the presence of follicular cells and tunica albuginea There may be hundreds or even millions of fertile eggs present in the ovary of a fish at any given time.
Fresh eggs may be developing from the germinal epithelium throughout life. Corpora lutea are found only in mammals, and in some elasmobranch fish; in other species, the remnants of the follicle are quickly resorbed by the ovary.
In some elasmobranchs, only the right ovary develops fully. In the primitive jawless fish and some teleosts, there is only one ovary, formed by the fusion of the paired organs in the embryo.
Fish ovaries may be of three types: gymnovarian, secondary gymnovarian or cystovarian. In the first type, the oocytes are released directly into the coelomic cavity and then enter the ostium , then through the oviduct and are eliminated.
Secondary gymnovarian ovaries shed ova into the coelom from which they go directly into the oviduct. In the third type, the oocytes are conveyed to the exterior through the oviduct. Cystovaries characterize most teleosts, where the ovary lumen has continuity with the oviduct.
Fish typically have quite small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal. Fish brains are divided into several regions. At the front are the olfactory lobes , a pair of structures that receive and process signals from the nostrils via the two olfactory nerves.
The olfactory lobes are very large in fish that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed telencephalon , the structural equivalent to the cerebrum in higher vertebrates.
In fish the telencephalon is concerned mostly with olfaction. The forebrain is connected to the midbrain via the diencephalon in the diagram, this structure is below the optic lobes and consequently not visible.
The diencephalon performs functions associated with hormones and homeostasis. This structure detects light, maintains circadian rhythms, and controls color changes. These are very large in species that hunt by sight, such as rainbow trout and cichlids. The hindbrain or metencephalon is particularly involved in swimming and balance.
The brain stem or myelencephalon is the brain's posterior. Vertebrates are the only chordate group to exhibit a proper brain. A slight swelling of the anterior end of the dorsal nerve cord is found in the lancelet, though it lacks the eyes and other complex sense organs comparable to those of vertebrates.
Other chordates do not show any trends towards cephalisation. The front end of the nerve tube is expanded by a thickening of the walls and expansion of the central canal of spinal cord into three primary brain vesicles; the prosencephalon forebrain , mesencephalon midbrain and rhombencephalon hindbrain then further differentiated in the various vertebrate groups.
Vesicles of the forebrain are usually paired, giving rise to hemispheres like the cerebral hemispheres in mammals. The circuits in the cerebellum are similar across all classes of vertebrates, including fish, reptiles, birds, and mammals. There is considerable variation in the size and shape of the cerebellum in different vertebrate species.
In amphibians, lampreys, and hagfish, the cerebellum is little developed; in the latter two groups, it is barely distinguishable from the brain-stem. Although the spinocerebellum is present in these groups, the primary structures are small paired nuclei corresponding to the vestibulocerebellum.
The cerebellum of cartilaginous and bony fishes is extraordinarily large and complex. In at least one important respect, it differs in internal structure from the mammalian cerebellum: The fish cerebellum does not contain discrete deep cerebellar nuclei.
Instead, the primary targets of Purkinje cells are a distinct type of cell distributed across the cerebellar cortex, a type not seen in mammals. In mormyrids a family of weakly electrosensitive freshwater fish , the cerebellum is considerably larger than the rest of the brain put together.
The largest part of it is a special structure called the valvula , which has an unusually regular architecture and receives much of its input from the electrosensory system.
Most species of fish and amphibians possess a lateral line system that senses pressure waves in water. One of the brain areas that receives primary input from the lateral line organ, the medial octavolateral nucleus, has a cerebellum-like structure, with granule cells and parallel fibers.
In electrosensitive fish, the input from the electrosensory system goes to the dorsal octavolateral nucleus, which also has a cerebellum-like structure. In ray-finned fishes by far the largest group , the optic tectum has a layer—the marginal layer—that is cerebellum-like. A neuron is "identified" if it has properties that distinguish it from every other neuron in the same animal—properties such as location, neurotransmitter , gene expression pattern, and connectivity—and if every individual organism belonging to the same species has one and only one neuron with the same set of properties.
In simpler nervous systems, some or all neurons may be thus unique. In vertebrates, the best known identified neurons are the gigantic Mauthner cells of fish. Each Mauthner cell has an axon that crosses over, innervating neurons at the same brain level and then travelling down through the spinal cord, making numerous connections as it goes.
The synapses generated by a Mauthner cell are so powerful that a single action potential gives rise to a major behavioral response: within milliseconds the fish curves its body into a C-shape , then straightens, thereby propelling itself rapidly forward.
Functionally, this is a fast escape response , triggered most easily by a strong sound wave or pressure wave impinging on the lateral line organ of the fish. Mauthner cells are not the only identified neurons in fish—there are about 20 more types, including pairs of "Mauthner cell analogs" in each spinal segmental nucleus.
Although a Mauthner cell is capable of bringing about an escape response all by itself, in the context of ordinary behavior, other types of cells usually contribute to shaping the amplitude and direction of the response.
Mauthner cells have been described as command neurons. A command neuron is a special type of identified neuron, defined as a neuron that is capable of driving a specific behavior all by itself. The concept of a command neuron has, however, become controversial, because of studies showing that some neurons that initially appeared to fit the description were really only capable of evoking a response in a limited set of circumstances.
Immune organs vary by type of fish. These fish rely on regions of lymphoid tissue within other organs to produce immune cells. For example, erythrocytes , macrophages and plasma cells are produced in the anterior kidney or pronephros and some areas of the gut where granulocytes mature.
They resemble primitive bone marrow in hagfish. Cartilaginous fish sharks and rays have a more advanced immune system. They have three specialized organs that are unique to chondrichthyes ; the epigonal organs lymphoid tissues similar to mammalian bone that surround the gonads, the Leydig's organ within the walls of their esophagus, and a spiral valve in their intestine.
These organs house typical immune cells granulocytes, lymphocytes and plasma cells. They also possess an identifiable thymus and a well-developed spleen their most important immune organ where various lymphocytes , plasma cells and macrophages develop and are stored. Chondrostean fish sturgeons, paddlefish and bichirs possess a major site for the production of granulocytes within a mass that is associated with the meninges , the membranes surrounding the central nervous system.
Their heart is frequently covered with tissue that contains lymphocytes, reticular cells and a small number of macrophages. The chondrostean kidney is an important hemopoietic organ; it is where erythrocytes, granulocytes, lymphocytes and macrophages develop. Like chondrostean fish, the major immune tissues of bony fish teleostei include the kidney especially the anterior kidney , which houses many different immune cells.
in the skin, gills, gut and gonads. Much like the mammalian immune system, teleost erythrocytes, neutrophils and granulocytes are believed to reside in the spleen whereas lymphocytes are the major cell type found in the thymus.
Although not confirmed as yet, this system presumably will be where unstimulated naive T cells accumulate while waiting to encounter an antigen. Contents move to sidebar hide. Article Talk. Read Edit View history. Tools Tools. What links here Related changes Upload file Special pages Permanent link Page information Cite this page Get shortened URL Download QR code Wikidata item.
Download as PDF Printable version. In other projects. Wikimedia Commons. Study of the form or morphology of fishes.
External anatomy of a bony fish Hector's lanternfish : 1. operculum gill cover , 2. lateral line , 3. dorsal fin , 4. adipose fin , 5. caudal peduncle , 6. caudal fin , 7. anal fin , 8. photophores , 9. pelvic fins paired , pectoral fins paired. See also: Fish bone.
The X-ray tetra Pristella maxillaris has a visible backbone. The spinal cord is housed within its backbone. A vertebra diameter 5 mm 0. Skull of a northern pike. Skull of Tiktaalik , a genus of extinct sarcopterygian lobe-finned "fish" from the late Devonian period.
Main article: Fish jaw. See also: Shark tooth. Zenion hololepis is a small deep water fish with large eyes. The deep sea half-naked hatchetfish has eyes which look overhead where it can see the silhouettes of prey. See also: Vision in fish. Main article: Fish gill. See also: Fish respiration.
Main article: Fish scale. Fish scales: 1. cycloid scale; 2. ctenoid scale; 3. placcoid scale; 4. ganoid scale. Main article: Lateral line.
Main article: Photophores. Main article: Fish fin. This section is an excerpt from Bladder § Fish. Most fish also have an organ called a swim-bladder which is unrelated to the urinary bladder except in its membranous nature. The loaches , pilchards , and herrings are among the few types of fish in which a urinary bladder is poorly developed.
It is largest in those fish which lack an air bladder, and is situated in front of the oviducts and behind the rectum. Main article: Swim bladder. Main article: Fish reproduction. See also: Reproductive processes in fish.
See also: Brain § Vertebrates. See also: Fish diseases and parasites. Anatomical terms of location Decapod anatomy Digital Fish Library Evolution of fish Fish development Fish measurement Fish physiology Gastropod anatomy Ichthyology terms Panderichthys digits Shark anatomy.
Ladd 18 March In Prosser, C. Ladd ed. Environmental and metabolic animal physiology. New York: Wiley-Liss. ISBN X. OCLC Archived from the original on 3 July Image courtesy of NOAA Ocean Explorer.
A Otolith ear bone of an American barrelfish B A pair of otoliths from a lb eight-banded grouper. Like the otoliths in human ears, otoliths in fishes help with hearing and with balance.
When a fish changes position, the otoliths bump the hair cells in the ampullae. The ampullae are bulges in the semicircular canals of the ears Fig 4. Some fishes also use other organs to aid in hearing.
For example, the gas bladder changes volume in response to sound waves. Some fishes can detect these changes in gas bladder volume and use them to interpret sounds. Most mammals get oxygen from the air, but most fishes get oxygen from the water. To get oxygen from the water, fish must pass water over their gills.
Gills are composed of a gill arch, gill filaments, and gill rakers see Fig. In many fishes the gill arch is a hard structure that supports the gill filaments. The gill filaments are soft with lots of blood vessels to absorb oxygen from the water.
Image Courtesy of National Oceanic and Atmospheric Administratrion NOAA. Image courtesy of National Oceanic and Atmospheric Administration NOAA. C A drawing of a gill showing gill filaments oxygen absorption , gill arch supporting structure , and gill rakers comb like structure for filtering.
A A bony fish with the operculum held open to show the gills B A single gill removed from a bony fish C A drawing of a gill showing gill filaments oxygen absorption , gill arch supporting structure , and gill rakers comb like structure for filtering.
Some fishes, like tunas, need to continuously swim to get oxygen from the water. Other fishes, like wrasses, can pass water over their gills by pumping it. This enables wrasses to remain motionless and still get oxygen.
Fishes get both oxygen and food from water. To get oxygen, water needs to move toward the gills. The gill rakers are comb-like structures that filter food from the water before it heads to the gills.
Fish that eat small prey like plankton tend to have many long, thin gill rakers to filter very small prey from the water as it passes from the mouth to the gills.
On the other hand, fish that eat large prey tend to have more widely spaced gill rakers, because the gill rakers do not need to catch tiny particles.
In chimeras and bony fishes, the operculum covers the posterior end of the head, which protects the gill openings. The bony operculum often has another bony flap, called the preoperculum , overlaying it Fig. Some fishes also have a strong spine, or spines, that project back from the preoperculum or operculum.
These spines are usually used for protection. Sharks and rays have open, naked gills see Table 4. Their classification name, elasmobranch , actually means naked gill. Most elasmobranchs have five gill openings—exceptions include the six gill and seven gill shark.
A A semicircle angelfish Pomacanthus semicirculatus with bright blue highlight color on the preoperculum, preoperculum spine, and operculum. Image by Stan Shebs. B A dog snapper Neomaenis jocu with preoperculum, operculum, and operculum spine labeled.
A A semicircle angelfish Pomacanthus semicirculatus with bright blue highlight color on the preoperculum, preoperculum spine, and operculum B A dog snapper Neomaenis jocu with preoperculum, operculum, and operculum spine labeled.
The buccal pump is what fish use to move water over their gills when they are not swimming. The buccal pump has two parts: the mouth and the operculum. During the first stage of pumping, both opercula close, and the mouth opens. Water then enters through the mouth.
Next, the fish closes its mouth and opens its opercula so that water moves over the gills, which remove oxygen from the water. Some fishes also use the buccal pump as part of their feeding strategy by filtering out small organisms living in the water as they pump water Fig.
As water passes through, the gill rakers help to trap plankton from the water. Some fishes feed by filtering out through their buccal pump such as this whale shark, which feeds on plankton. A pore is a small opening in the skin. A typical fish has anal, genital, and urinary pores located anterior of the anal fin.
The anal pore is where feces exits the fish body. The anus is the largest and most anterior of the pores Fig. The genital pore is where eggs or sperm are released. The urinary pore is where urine exits the body. Often the genital and urinary pore are combined into a single urogenital pore.
These pores are situated on a small papilla, or bump, just behind the anus Fig. Most fishes reproduce externally, meaning that the sperm and eggs meet outside their bodies.
However, some fishes reproduce internally. The females of these fishes often have a genital pore that is modified for internal fertilization. Different fishes have different types of scales. These different types of scales are made of different types of tissue Fig.
Types of scales also correspond to evolutionary relationships Fig. Placoid scales are found in the sharks and rays Fig. Placoid scales are made of a flattened base with a spine protruding towards the rear of the fish. These scales are often called dermal denticles because they are made from dentin and enamel, which is similar to the material teeth are made of.
Ganoid scales are flat and do not overlap very much on the body of the fish Fig. They are found on gars and paddlefishes. In the sturgeon, ganoid scales are modified into body plates called scutes. Cycloid and Ctenoid scales are found in the vast majority of bony fishes Figs 4. These types of scales can overlap like shingles on a roof, which gives more flexibility to the fish.
These scales also form growth rings like trees that can be used for determining age. Ctenoid scales are different than cycloid scales in that cycloid scales tend to be more oval in shape. Ctenoid scales are more clam shaped and have spines over one edge.
Cycloid scales are found on fishes such as eels, goldfish, and trout. Ctenoid scales are found on fishes like perches, wrasses, and parrotfish.
Some flatfishes, like flounder, have both cycloid and ctenoid scales. Four types of fish scales A Placoid, B Ganoid, C Cycloid, and D Ctenoid. Scale size varies greatly among species, and not all fishes have scales. Some fishes, like some rays, eels, and blennies, do not have any scales.
This is probably because these fishes spend a lot of time rubbing on the sand or in rocks. If they had scales, the scales would likely rub off. At the other extreme, some fishes have scales modified into bony plates, such as on a sturgeon and pinecone fish Fig. Other fish have scales modified into spines for protection, like the porcupine fish Fig.
Fishes are very diverse, and there are examples of extreme body modifications in many different groups of fishes see Table 4. For example, some fishes, like angler fish, have lures to attract prey.
Others, like lionfish, have poison sacs to protect them from predators. Color The color of fishes is very diverse and depends on where a fish lives.
Color can be used as camouflage. Color also plays a role in finding mates, in advertising services like cleaning, in attracting prey, and in warning other fishes of danger see Table 4.
Tunas, barracuda, sharks, and other fishes that live in the open ocean are often silvery or deep blue in color. These fishes also have a body coloring pattern called counter shading. Counter shading means dark on the dorsal, or top, surface and light on the ventral, or belly side.
Countershading helps to camouflage fishes by matching the dark, deep water when viewed from above and matching the light, surface water, when viewed from below Fig. Image courtesy of Fbattail. Nearer to shore, many fishes have also evolved to be camouflaged in their environment.
Kelpfish have developed both colors and a body shape that helps them blend in with the seaweed that they live in. Reef fish often look like coral. Fishes that hide in the sand, like blennies, flat fish, and flounder, are often a speckled sandy color Fig.
Image courtesy of EyeKarma. Image courtesy of Jason Marks. Many brightly colored fishes that live in coral reef habitats also use their color, stripes, and spots as camouflage Fig.
This is partly because wavelengths of light, and therefore color, appear different under water and change with depth and water color. Water absorbs light.
Thus, the amount of light decreases with increasing depth. Red color, for example, fades out very fast with increasing depth. Fishes with red color, like soldierfish Fig. Yellow and blue colors, on the other hand, blend in with the reef color, also providing camouflage from predators Fig.
Even stripes and spots can prevent an individual fish from standing out, making it harder for a predator to strike Fig. A Soldierfish B blue and yellow Hawaiian cleaner wrasse C school of convict tang and whitebar surgeonfish.
In addition to colors visible to humans, fish also use ultraviolet UV light colors for camouflage and communication. Some fishes can see using UV light, and so they use UV colors to identify each other and to avoid predators. Many reef fish can also blink their colors on and off to flash messages Fig.
Skin cells called chromatophores allow fish and other animals to quickly change skin color. Examples of color-changing fish. It can rapidly change skin colors. Image courtesy of Brocken Inaglory , Wikimedia Commons.
Image Courtesy of Wikimedia Commons. Image Courtesy of Hans-Petter Fjeld. Image Courtsey of Wikimedia Commons. Living things are composed of cells. Cells often become specialized to perform certain functions.
For example, muscle cells contract, nerve cells transmit impulses, and gland cells produce chemicals. A tissue is a group of similar cells performing a similar function Fig.
There are many kinds of tissues—bone, cartilage, blood, fat, tendon, skin, and scales. An organ is a group of different kinds of tissues working together to perform a specific function Fig.
The stomach is an example of an organ made of several types of tissues. An organ system is a group of organs that together perform a function for the body. The digestive system, for example, consists of organs such as the mouth, the stomach, and the intestine Fig.
These organs work together to break down food and provide nutrients to the body. An organism is an entire living thing with all its organ systems Fig. A complex organism like a fish has digestive, nervous, sensory, reproductive, and many other systems. Fish consist of interacting groups of organ systems that together enable a fish to function.
The integumentary system is commonly called the skin. It consists of two layers, the epidermis, or outer layer, and the dermis, or inner layer. Beneath these are the muscles and other tissues that the skin covers Fig. Image courtesy of Rajesh dangi. B A drawing of the skin and integumentary system of a fish, showing scales, epidermis, dermis, and muscle.
The epidermis is the top layer of the integumentary system. It is made of several sheets of cells that cover the scales. As the cells age, new cells growing underneath push older cells toward the outer surface.
In the epidermis of most fishes are cells that produce mucus, a slippery material like runny gelatin, that helps the fish slide through the water. The mucus wears off daily, carrying away microscopic organisms and other irritants that might harm the fish. The odor typical of most fish comes from chemicals in the mucus.
In their epidermis, fishes have cells containing pigment grains that give the fish its color. Some fish can change color by expanding or contracting pigment cells. The changes are controlled by hormones that are produced by the endocrine system and regulated by the nervous system.
The lower layer of the integumentary system contains blood vessels, nerves for sensing touch and vibration, and connective tissue made of strong fibers. A special layer of dermal cells secretes chemicals to produce scales, which grow larger as the fish grows.
Most fish have covering scales that protect them from damage when they bump into things or are attacked. As the scales grow, they form concentric rings in some fishes. A few fish, such as catfish, have no scales. The skeletal system supports the soft tissues and organs of the fish Fig.
The skeleton also protects organs and gives the body of the fish its basic shape. The many bones of the skull form a rigid box that protects the brain. Holes, hinges, and pockets in the skull allow room for the nostrils, mouth, and eyes.
The vertebral column , or backbone, is not a solid rod. The backbone is actually a string of small bones called vertebrae. Each vertebra has a small hole in it. Together, the small holes in the vertebrae form a canal through which the spinal cord passes.
The vertebrae bones protect the spinal cord. Spaces between the vertebrae allow the backbone to bend and nerves to reach the tissues and organs of the body.
Rib bones protect the body cavity. Additional bones support the spines and rays. Image Courtesy of Assianir. B A drawing of a fish skeleton vertebrae viewed from the front, showing rib and tail sections.
Muscles are tissues that contract to shorten and relax to lengthen. Fish move by contracting and relaxing their muscles. Like humans, fish have three types of muscles: skeletal muscles, smooth muscles, and heart muscles.
The muscles and bones of a fish work together. Skeletal muscles use bones as levers to move the body. Tendons are strong connective tissues that attach muscle to bone. When muscle cells are stimulated, they contract and shorten, which pulls on tendons to move bones.
Skeletal muscles are voluntary, meaning that they move only when the thinking part of the brain signals them to move. To swim, fish must contract and relax their skeletal muscles, just as humans do when they learn to walk.
These layers are arranged in W-shaped bands from belly to back Fig. This network of muscles is vertical and interlocking, which allows the fish to move the body back and forth in a smooth, undulating motion. Such motion would not be possible if the muscles ran horizontally along the length of the body, from head to tail.
This chapter highlights the major consistencies and differences that are evident in the anatomy and physiology of those fish most likely to be encountered by the veterinarian or biologist working in the realm of aquatic animal health. It describes teleost fish, members of the infraclass Teleostei that includes bony fish with protrusible upper jaws, as these represent the majority of species commonly encountered in clinical or research settings.
The chapter provides the more commonly encountered non-teleost fish including other bony fish like lungfish, sturgeons, and gars as well as the elasmobranchs. There are a number of external anatomical landmarks that are well conserved among fish.
Fish may be subdivided into three anatomical regions: head, body, and tail. Sensory organs may figure prominently among the external anatomy of fish. A unique hallmark of the skin of many fish is their coloration, resultant from the pigment cells, or chromatophores, contained in the dermis. Science Explorer.
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Fish anatomy Thermogenesis and weight management the Physioloty of the form or morphology of Immune system optimization strategies. It can be contrasted with fish physiologywhich is the study of Fidh the component parts of fish function Anato,y in the living Physiolovy. The anatomy Physiologyy fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage cartilaginous fish or bone bony fish.
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