Many fishes, like goatfish and catfish, also have fleshy structures called barbels around the chin, mouth, and nostrils see Table 4. In some fishes, these barbels are used for touch and chemoreception. Not all barbels have chemoreception. The barbels of some fish, like catfishes, are not equipped for chemical reception Fig.
Some fish also have fleshy tabs called cirri on the head Fig. Cirri are not sensory organs. Lateral line Most fish have a structure called the lateral line that runs the length of the body—from just behind the head to the caudal peduncle Fig. The lateral line is used to help fishes sense vibrations in the water. Vibrations can come from prey, predators, other fishes in a school, or environmental obstacles.
The lateral line is actually a row of small pits that contain special sensory hair cells Fig. These hair cells move in response to motion near the fish. The lateral line sense is useful in hunting prey, escaping predators, and schooling. Ampullary receptors are sense organs made of jelly-filled pores that detect electricity. They can detect low frequency alternating current AC and direct current DC.
Fishes that have ampullae include sharks, sturgeon, lungfish, and elephant fish. The ampullae of sharks are known as Ampullae of Lorenzini—named for Stefano Lorenzini, who first described them in Fig. Fig 4. Some fishes can also generate their own electrical fields.
These fishes have both ampullae type receptors and tuberous type receptors. The tuberous receptors are most sensitive to the electric organ discharge of the fish itself, which is important for object detection.
The tuberous type of receptor is usually deeper in the skin than ampullae. Some fishes that produce electricity also use it for communication. Electric fishes communicate by generating an electric field that another fish can detect. For example, elephant fishes use electrical communication for identification, warning, submission, courtship, and schooling Fig.
Sound travels well underwater, and hearing is important to most fishes. Fishes have two inner ears embedded in spaces in their skulls. The lower chambers, the sacculus and the lagena, detect sound vibrations. See Fig. Each ear chamber contains an otolith and is lined with sensory hairs. Otoliths are small, stone-like bones See Fig. They float in the fluid that fills the ear chambers. Otoliths lightly touch the sensory hair cells, which are sensitive to sound and movement.
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. 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 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.
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.
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.
A A leafy seadragon hiding in kelp B A blenny hiding in coral C A three-spot flounder hiding in sand. 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. 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. 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.
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.
A Side view of salmon skeletal muscle B Drawing of skeletal muscle pattern in a fish. A fish swims by alternately contracting muscles on either side of its body See Fig. Swimming begins when the muscles on one side of the body contract, pulling the caudal fin toward that side. The sideways movement of the caudal fin pushes the fish forward. Then the muscles on the opposite side of the body contract, and the caudal fin moves toward the other side of the body.
A Sardines swim by contracting their tail muscles B A drawing contrasting a typical fish swimming movement with the movement of a typical human swimming with dive fins. Fishes with wide pectoral fins, like wrasses, swim by flapping their pectoral fins. Other fishes, like fast-swimming tunas, move mostly with their caudal fin but use long, thin pectoral fins for steering.
Skeletal muscles also move dorsal fins. Faster-swimming fishes reduce water drag by tucking in their dorsal fins while swimming.
Slower-swimming reef fishes have larger dorsal fins, which they sometimes flare to protect themselves in encounters with other fish. Smooth muscles move internal organs of the body and line tubes such as the intestinal tract and blood vessels. Smooth muscles are involuntary; they move without signals from the thinking part of the brain.
For example, smooth muscles automatically contract and relax to push food through the digestive tract from the mouth to the anus. Other smooth muscles control the flow of blood and other body fluids and movement in the urogenital tract. Heart muscles are also involuntary.
However, the structure of heart muscle cells is different from involuntary smooth muscles, so these two muscle types are given separate names. Heart muscles pump blood through the blood vessels by rhythmically contracting and relaxing.
Respiratory System The respiratory system takes oxygen O2 into the body and passes carbon dioxide CO2 out of the body. The respiratory organs in fish are gills. Each gill has many gill filaments, which contain a network of tiny blood vessels called capillaries Fig. The gill cover also called the operculum is the body surface that covers the gills. The gill rakers filter food from the water as water passes out to the gills.
A Exposed fish gills as viewed from the ventral, or belly side, of the head B A drawing of a gill filament with a gill raker and the gill arch labeled. Water moves over the gills in a pumping action with two steps Fig.
In the first step, the mouth opens, the gill covers close, and the fish brings water into its mouth. In the second step, the mouth closes, the gill covers open, and water passes out of the fish. This action is called buccal pumping and is named for the cheek muscles that pull water into the mouth and over the gills. Some fish also use ram ventilation to move water over their gills.
When swimming fast, fish like sharks and tunas open both their mouths and gill openings to let water pass continuously through their gills. They do not need to open and close their mouth because water is pushed over their gills by their swimming action. As water passes over the gills, carbon dioxide in the blood passes into the water through the capillaries of the gill filaments. In the first gill arch, both species of Parapimelodus and H.
These three species showed the smallest distance between the gill rakers, followed by S. In the second, third and fourth arches, both species of Parapimelodus and H. The highest spine length in the first gill arch was found in H. In the second and third gill arch, P. The highest spine length in the fourth gill arch was found in S. Parapimelodus valenciennis showed the lowest spine length in the fourth arch. Hypostomus commersonii did not show any significant differences from the other species.
In the first gill arch, H. No significant difference in this parameter was found among the other species. In the second gill arch, the distance between spines was higher in both species of Parapimelodus. In the third gill arch, this distance was the highest in P. Both species of Parapimelodus showed a higher distance between spines in the fourth arch than H.
The length of the gill rakers increased in proportion to the length of the fish in P. The distance between gill rakers also increased with fish length in the first and second gill arches of P. The spine length and the distance between spines had a weak relationship with fish length in all gill arches except the first gill arch of I.
The gill rakers of H. The gill rakers of S. Both species show spines covering the rakers. Hoplias lacerdae Miranda Ribeiro, ; Erythrinidae , a piscivorous species, shows the same pattern found in H. The same characteristics found in S. The gill rakers of I. The widely spaced gill rakers of this species allow the retention of larvae, whereas particles of inorganic matter, such as sand, are rejected FUGI et al.
The species of Parapimelodus analyzed in the present study have long, filiform and closely spaced gill rakers. It is probable that both species of Parapimelodus use filtering to feed and that the gill rakers act as a filter for retaining particles. The first gill arch presents longer gill rakers in most species analyzed in the present study.
The relationship between fish length and gill raker length detected in most of the species examined in the present study is also found in A. During growth in C.
A possible explanation of these changes is that juveniles ingest smaller particles than do adults, but difference in prey ingestion with age may also reflect changes in fish swimming abilities ROSS et al. The present study found that the distance between gill rakers increased with fish length only in P.
In addition, instead of dead-end filtration, several planktivore species use crossflow filtration, in which the major flow is parallel to the filter surface and particles aggregate together on the surface of the filter to form clumps that are much larger than the apparent pore size ROSS et al. The results of the present study demonstrated that the characteristics of the gill rakers rakers and spines length, distance between rakers and spines may vary between gill arches of the same species, and also with the fish size.
Therefore, comparisons between species must be between fish of the same size and with the same gill arch. The characteristics of the gill rakers of the studied species allow the conclusion that these structures show adaptations related to the diet of the fish but that morphological variation may also occur, even between species that show the same feeding habit.
In general, gill raker length and the distance between gill rakers showed a positive relationship with fish length.
However, there was no relationship between fish length and spine length or the distance between spines. Abrir menu Brasil. Abrir menu. Key words: filtering, gill arches, feeding behavior. ABES, S. Brazilian Archives of Biology and Technology , v. Accessed: Dez. BEHR, E. Accessed: 20 dez. Relationship between morphology and diets of six neotropical loricariids. Journal of Fish Biology , v. Gills of the freshwater fish Hypostomus commersonii Val. FUGI, R. Trophic morphology of five benthic-feeding fish species of a tropical floodplain.
Revista Brasileira de Biologia , v. HAHN, N. Morphology of the pharyngeal cavity, especially the surface ultrastructure of gill arches and gill rakers in relation to the feeding ecology of the catfish Rita rita Siluriformes, Bagridae.
0コメント