The digestive system of fish consists of the digestive tract and glands. Fish are divided into omnivores, detritophages, predators and herbivores. Herbivores eat microalgae, aquatic flowering plants, plankton. Some marine ones feed on macroalgae. Predators use crustaceans, mollusks, worms and small fish, parasites and dead parts of other fish for a food resource. Some varieties change their diet over the course of their life, from plankton to fish and invertebrates. The species, work and importance of the digestive system in fish will be discussed in this article.
In most fish, the oral cavity is equipped with many conical teeth designed to capture and hold food. It does not delimit with the pharynx, which leads into the short esophagus. The stomach has a variety of shapes and sizes. Its ability in deep-sea predatory fish to stretch helps them to stock up on food.
Partial processing of food in the stomach occurs under the influence of juice, which is produced by small glands of the mucous membrane. Food is completely processed and absorbed in the small intestine. To increase the surface of digestion in the upper part there are blind processes. The secret produced by the pancreas through the ducts flows into the initial section of the intestine. There also comes bile. Undigested food debris accumulates in the hind gut, which is removed through the anus.
In fish, it consists of five sections: the oral cavity, pharynx, esophagus and stomach, which serves to partially digest food. In addition, there is an intestine in which the final absorption of food, nutrients and waste through the anus occurs. The quality of nutrition is reflected in the digestive system of fish, and it can vary significantly between different breeds. Large-sized species have a mouth in the form of a special suction funnel inside equipped with teeth. Fish stick to their prey, drilling a body with a sharp tongue. In the wound, they secrete a substance that partially dissolves the protein. Already partially processed food enters the gastrointestinal tract.
The mouth included in the digestive system in predator fish is a grabbing tool with sharp teeth, which are often located in several rows and hold the prey tight.
The teeth have no roots and do not last long, and then new ones grow. They can be located not only on the jaw, but also in other places of the oral cavity, including the tongue. Predators have sharp teeth that are bent back, they are even in the throat. And many peaceful breeds do not have teeth at all.
From the mouth, food enters the next section of the digestive system of the fish - the pharynx. It contains gill slots that open outwards. There are stamens on the gills.
They help predators to retain prey and protect against gill damage. Other fish filter the water through the latter and retain the feed. In addition, in the throat are glands that produce mucus, which helps swallow.
Esophagus and stomach
The pharynx passes into the esophagus, which is a small organ of the digestive system of fish, passing into the stomach, which helps to promote feed. In puffer fish, the esophagus can swell, filling with air. In sharks, stingrays and salmon, it consists of two sections, and in perches, a blind process. Some aquatic inhabitants have no stomach at all, and the esophagus is replaced by the intestines.
The esophagus passes into the intestine, which begins with the small intestine. Two ducts flow into it from:
- bile delivery liver
- pancreas with catalysts (enzymes).
These components contribute to the breakdown of proteins into amino acids, fats into fatty acids and glycerin, and polysaccharides into sugars. After splitting, nutrients are absorbed into the blood through the folded walls of the stomach, equipped with outgrowths and penetrated by lymphatic vessels and capillaries. A feature of the digestive system of fish is the length of the intestine. It is directly dependent on the calorie content of food. In predators, it is short, and in fish that feed on plankton, it is long. The intestine of silver carp is 16 times longer than its own size. In all species of fish, it ends with an anus located between the genital and urinary tract.
Liver and pancreas
Considering the structure of the digestive system of fish, it should be said that it includes the liver and pancreas. The enzymes they produce flow through the ducts into the small intestine. Cartilaginous fish species have a three-lobed liver, and bony - from one to three. It makes up to 20% of the total weight of the fish. Bile produced by the liver stimulates the intestines by breaking down fats. This body neutralizes toxic substances, synthesizes carbohydrates and proteins, and stores vitamins and glycogen. All this is necessary for adequate body activity. The pancreas synthesizes enzyme substances that affect food processing. In addition, it produces insulin, which regulates the concentration of glucose in the blood. In some fish (such as cyprinids), pancreatic tissue is found in the liver. In fish that feed on plant foods, microorganisms located in the intestines and secrete enzymes are involved in the processing of nutrients.
Digestive system of cartilaginous fish
Cartilaginous fish are mainly inhabitants of salt bodies of water, but some species exist beautifully in fresh water. This species belongs to predators and feeds on small relatives and near-bottom crayfish, crabs, mollusks, and sometimes jellyfish. Due to the special shape of the body, cartilaginous fish move quickly and have jaws with very sharp teeth, a real language is missing.
Their skeleton consists entirely of cartilage, there are no gill covers and there is no swim bladder. The digestive system of cartilaginous fish consists of an oral cavity, a pharynx with gill slits, a short esophagus, which has muscular walls and a stomach. The breakdown and assimilation of food occurs in the small intestine, which has a folded inner surface and a small length that ends in the anus. Cartilaginous fish retain cloaca. The digestive system of fish is performed by the liver, gall bladder and pancreas. They produce enzymes that enter the upper part of the small intestine through the ducts and help break down nutrients into amino acids, vitamins, and fatty acids. It should be noted that the pancreas in cartilaginous fish is an independent organ and is located separately, and the large liver consists of three lobes and makes up to 20% of body weight.
Digestion features of bone fish
The digestive system of bone fish has the same departments as cartilaginous. The location of the mouth depends on the type of food. There are many teeth in the oral cavity. All of them are of the same type with a slope to the throat and are adapted only to capture and hold food. The pharynx with gill slits is actively involved in the nutrition process. In some species of fish, powerful and large pharyngeal teeth for grinding food are located in the throat on the branchial arch. The short esophagus passes into the stomach, which is not present in all fish species.
After the stomach, food enters the small intestine. At its very beginning there are ducts of the liver and pancreas. It is here that the breakdown and assimilation of food occurs. In bone fish, the small intestine is much longer than in cartilaginous. It forms a loop, which increases the surface of the suction. Many species of fish when moving the stomach into the small intestine have appendages for the breakdown of protein and absorption of amino acids. Bone fish have a gall bladder and multi-lobed liver, which may consist of 1-3 lobes. The structures of the pancreas, unlike cartilaginous fish, are found in the tissues of the liver. The small intestine smoothly passes into the large and ends with the anus.
Features of the digestive system of sturgeons
Sturgeons have a digestive tract, which occupies in its structure an intermediate place between cartilage and bone fish. All sturgeons have a retractable jaw apparatus, representing a mouth funnel. Its ability to move far out allows you to collect food from the bottom of the reservoir. Teeth are present only in larvae. In adults, they are replaced by horn rollers. In the digestive system, sturgeons have two devices that increase the absorption surface area:
- like bone, the intestines create several loops,
- like cartilage, the middle intestines retain a spiral fold.
In sturgeons on the walls of the intestine, fused appendages form a pyloric gland, which opens into the intestine. Instead of cesspools, two openings: genitourinary and anal. The digestive tract has the same departments as the vertebrates. An irregularly shaped liver occupies the entire front of the body and consists of three lobes. The shape of the gallbladder is oval. Its ducts flow into the duodenum. The pancreas is an independent organ.
Digestive system classification of fish
The digestive tract in fish is much simpler in structure than in higher vertebrates. But a wide variety of fish species and structural features of their gastrointestinal tract are still not fully understood. To facilitate work in this direction, all types of fish by the type of digestive system were divided into:
- salmon - a stomach with thin walls, pyloric appendages from 80 to 400,
- perch - the walls of the pharynx are thick, the stomach is cylindrical, 3 pyloric appendages,
- pike - esophagus with thick walls, an elongated stomach, an elongated liver in body geometry,
- cyprinids - there is no stomach, the digestive tract is a thin tube consisting of several loops, there is an extension in the upper part of the intestine,
- acne - the esophagus is narrow and muscular, surrounded by the liver, it has several layers: mucous, submucous, muscular, serous, ciliary.
At first glance, fish digestion is simple. In fact, with a detailed study of this issue, it turns out that there are many devices that help them get and absorb food. Separate groups of fish developed under very different conditions.
Some of them turned out to be in fresh water, and the other in marine. There are fish species that can exist in a salty and fresh environment. Climatic conditions are also very different. As a result of this, in different regions there is a completely different food supply, to which the fish were forced to adapt. All this has led to a diversity of species and their digestive systems.
1. The common hauliod (Chauliodus sloani)
The Hauleyod family has 6 species of deep-sea fish, but the most common of these is the common Hauliod. These fish live in almost all the waters of the oceans, with the exception of the cold waters of the northern seas and the Arctic Ocean.
The hauliods got their name from the Greek words “chaulios” - an open mouth, and “odous” - a tooth. Indeed, in these relatively small fish (about 30 cm in length), teeth can grow up to 5 centimeters, which is why their mouth never closes, creating a terrible grin. Sometimes these fish are called marine vipers.
Howliodes live at a depth of 100 to 4,000 meters. At night, they prefer to rise closer to the surface of the water, and during the day fall into the very abyss of the ocean. Thus, during the day, fish make huge migrations of several kilometers. With the help of special photophores located on the body of a howliode, they can communicate with each other in the dark.
On the dorsal fin of the viper fish there is one large photophore, with which it lures its prey directly to the mouth. Then, with a sharp bite of teeth sharp as needles, howlioids paralyze the prey, leaving her no chance of salvation. The diet mainly includes small fish and crustaceans. According to false data, some individuals of howliodes can live up to 30 years or more.
2. Long-horned saber-toothed (Anoplogaster cornuta)
Long-horned saber-toothed is another frightening deep-sea predatory fish that lives in all four oceans. Although the saber-toothed looks like a monster, it grows to a very modest size (about 15 centimeters in length). The head of a fish with a large mouth occupies almost half the length of the body.
The long-horned saber-toothed got its name from the long and sharp lower fangs, which are the largest in relation to body length among all fish known to science. The terrifying look of the saber-toothed earned him an unofficial name - "monster fish."
The color of adults can vary from dark brown to black. Young representatives look completely different. They have a light gray color and long spikes on their heads. Sabretooth is one of the deepest fish in the world, in rare cases they sink to a depth of 5 kilometers or more. The pressure at these depths is huge, and the water temperature is about zero. Food is catastrophically scarce, so these predators prey on the first thing that gets in their way.
3. Dragon Fish (Grammatostomias flagellibarba)
The dimensions of a deep-sea dragon fish absolutely do not fit with its ferocity. These predators, which reach a length of no more than 15 centimeters, can eat prey two, or even three times its size. Dragon fish lives in tropical zones of the World Ocean at a depth of up to 2000 meters. The fish has a large head and mouth, equipped with many sharp teeth. Like Hawliod, the dragon fish has its own prey bait, which is a long mustache with a photophore at the end, located on the chin of the fish. The principle of hunting is the same as that of all deep-sea individuals. Using a photophore, a predator lures the prey to the closest possible distance, and then with a sharp movement inflicts a fatal bite.
4. Deep sea angler (Lophius piscatorius)
The deep-sea angler is rightfully the ugliest fish that exists today. In total there are about 200 species of anglerfish, some of which can grow up to 1.5 meters and weigh 30 kilograms. Because of its creepy appearance and bad character, this fish was called the devil. Deep-sea anglerfish live everywhere at a depth of 500 to 3,000 meters. The fish has a dark brown color, a large flat head with many spikes. A huge devil's mouth is dotted with sharp and long teeth, curved inward.
Deep-sea anglers have pronounced sexual dimorphism. Females are ten times larger than males and are predators. Females have a fishing rod with a fluorescent appendage at the end to fish. Anglers spend most of their time on the seabed, burying themselves in sand and silt. Due to the huge mouth, this fish can completely swallow prey, exceeding it in size by 2 times. That is, hypothetically, a large individual anglerfish can eat a person, fortunately there have never been such cases in history.
5. Sackcloth (Saccopharyngiformes)
Probably the most strange inhabitant of the sea depths can be called the sacculata or, as it is also called, the Pelican-shaped latitudinalus. Due to its abnormally large mouth with a sack and a tiny skull in relation to the length of the body, the sackcloth is more like some kind of alien creature. Some individuals can reach two meters in length.
In fact, the saccaliformes belong to the class of ray-finned fish, but there are not too many similarities between these monsters and cute fish that live in warm sea backwaters.Scientists believe that the appearance of these creatures changed many thousands of years ago due to a deep-sea lifestyle. Sackcloths have no gill rays, ribs, scales, and fins, and the body has an oblong shape with a luminous process on the tail. If it weren’t for the big mouth, the sackcloth could easily be confused with eel.
Sackcloth live at depths from 2000 to 5000 meters in three world oceans, except for the Arctic. Since there is very little food at such depths, the baggies have adapted to long breaks in meals, which can last more than one month. These fish feed on crustaceans and other deep-sea cousins, mainly swallowing their prey whole.
6. Giant Squid (Architeuthis dux)
The elusive giant squid, known to science as Architeutis Dux, is the largest mollusk in the world and is thought to be up to 18 meters long and weigh half a ton. At the moment, the living giant squid has not yet fallen into the hands of man. Until 2004, there were no documented cases of encountering a living giant squid, and a general idea of these mysterious creatures was formed only by the remains thrown ashore or caught in a network of fishermen. Architeutis live at a depth of 1 kilometer in all oceans. In addition to gigantic sizes, these creatures have the largest, among living creatures, eyes (up to 30 centimeters in diameter).
So in 1887, the largest instance of 17.4 meters long was thrown onto the coast of New Zealand. In the following century, only two large dead representatives of the giant squid were discovered - 9.2 and 8.6 meters. In 2006, the Japanese scientist Tsunemi Kubodera still managed to capture a live female 7 meters long in a natural habitat at a depth of 600 meters. The squid was lured to the surface with a small bait squid, but the attempt to deliver a live individual aboard the vessel was unsuccessful - the squid died from numerous injuries.
Giant squids are dangerous predators, and the only natural enemy for them are adult sperm whales. There are at least two described cases of squid and sperm whale fighting. In the first, the sperm whale won, but soon died, suffocating by the giant tentacles of the mollusk. The second battle took place off the coast of South Africa, then a giant squid fought with a sperm whale calf, and after an hour and a half battle still killed a whale.
7. Giant isopod (Bathynomus giganteus)
The giant isopod, known to science as Bathynomus giganteus, is the largest crustacean species. The average size of the deep-sea isopod ranges from 30 centimeters, but the largest recorded specimen weighed 2 kilograms and was 75 centimeters in length. In appearance, giant isopods are similar to wood lice, and like a giant squid are a consequence of deep-sea gigantism. These crayfish inhabit at a depth of 200 to 2500 meters, preferring to bury themselves in silt.
The body of these creepy creatures is covered with rigid plates that act as shells. In case of danger, the crayfish can curl up and become inaccessible to predators. By the way, isopods are also predators and can enjoy a few small deep-sea fish and sea cucumbers. Powerful jaws and strong armor make the isopod a dangerous adversary. Although giant crayfish love to eat live food, they often have to eat up the remains of shark prey that fall from the upper layers of the ocean.
8. Latimeria (Latimeria chalumnae)
Coelacanth or coelacanth is a large deep-sea fish, the discovery of which in 1938 became one of the most important zoological finds of the 20th century. Despite its unattractive appearance, this fish is notable for the fact that for 400 million years it has not changed its appearance and body structure. In fact, this unique relict fish is one of the oldest living creatures on planet Earth, which existed long before the advent of dinosaurs.
Latimeria lives at a depth of up to 700 meters in the waters of the Indian Ocean. The length of the fish can reach 1.8 meters with a weight of more than 100 kilograms, and the body has a beautiful blue tint. Since coelacanth is very slow, it prefers to hunt at great depths, where there is no competition with faster predators. These fish can swim backwards or belly up. Despite the fact that celicant meat is inedible, it is often the object of poaching among local residents. Currently, ancient fish is endangered.
9. Shark-Brownie or Mitzecurin (Mitsukurina owstoni)
The deep-sea shark-domovoy, or as it is also called the goblin shark, is the most poorly studied shark to date. This species lives in the Atlantic and Indian Ocean at a depth of up to 1300 meters. The largest instance was 3.8 meters long and weighed about 200 kilograms.
The goblin shark got its name due to its eerie appearance. Mitzecurin has movable jaws, which, when bitten, move out. For the first time, fishermen accidentally caught a shark-domovoy in 1898, and since then another 40 specimens of this fish have been caught.
10. Infernal Vampire (Vampyroteuthis infernalis)
Another relict representative of the sea abyss is the one-of-a-kind cephalopod mollusk-detritophagus, which resembles both the squid and the octopus. The hellish vampire got its unusual name due to its red body and eyes, which, however, depending on the lighting, can also be blue. Despite their terrifying appearance, these strange creatures grow up to only 30 centimeters and, unlike other cephalopods, eat exclusively plankton.
The body of a hellish vampire is covered with luminous photophores that create bright flashes of light that scare away enemies. In case of exceptional danger, these small mollusks twist their tentacles along the body, becoming like a ball with spikes. Infernal vampires live at depths of up to 900 meters, and can perfectly exist in water with a critical oxygen level of 3% or less for other animals.
Fish mouth location
- upper mouth type of fish (the lower jaw protrudes forward, the incision of the mouth is directed upwards - characteristic of the czechium)
- final type of fish mouth (jaws protrude identically, while the incision of the mouth is directed along the length of the body - typical for dace)
- bottom type of fish mouth (the snout protrudes above the lower jaw - characteristic of the podust).
Fish mouth shape
Fish mouth shape is transverse, oblique, lunate.
Fish that feed on bottom food usually have a lower or lower lower mouth type, while predators usually have a finite mouth type, and fish that take food from the surface of the water have an upper one.
Fish mouth may have other forms - funnel-shaped, tube-shaped and such fish mouth shape typical for the inhabitants of the sea, fish-like, and these are lampreys, mixins, have a mouth - suction cup.
Answer or solution 1
I take this opportunity and with your permission I will describe my aquarium guppies.
1) The shape of the body is elongated and flattened laterally.
2) males, the color is not uniform with a gradient brightness in the tail area, which gradually increases there (bright orange, if fundamentally). The body itself is gray, with specks of black.
Females are a nondescript uniform gray color that ends on the tail and flows smoothly into a similar black with blue pigment accents.
3) my pets do not have a pronounced lateral line as such. rather not visible.
4) my fish have a mouth rather located upstairs, there are scales.
5) The males have long fins, there are gonopodia - the anal fin, which has turned into a fertilization organ. The female has smaller fins and tail
when standing, the fins do not move much. not counting the tail. , chest heaving slightly.
when moving, it actively uses the caudal, pectoral, and dorsal fins.
7) It certainly exists: when a fish swallows a portion of water by mouth, the gill covers are closed, then the fish closes its mouth, a portion of water is driven through the gills and removed through the gill covers. Then the fish swallows the next portion of water.
8) the reaction of the males: sounds quickly float away from the source with a light blow by the fingers on the glass and hurry to lie low. He treats waved hands calmly, even having an interest in movements, involuntarily repeating them with his tail.
Females are the other way around, but the reaction is the same with a wave of hands.
9) at the time of fright, both experimental individuals showed themselves actively, quickly fingering their fins and moving their body, hiding at the bottom in coarse soil. In fry, the reaction is much faster.
something like this:)
Further, adjust and correct for yourself.