How does the fish breathe in the water? Very interesting question, it is not at all difficult to answer it. It breathes with gills, but how exactly does it happen, because water is not air? And do all fish have gills? But can they breathe atmospheric air? And how do they get oxygen from the water? So many questions arise immediately, if only to think about how you can breathe in the water. We will try to find answers to them.
Respiratory organs of fish
The main organ of respiration of fish are the gills. They are located near the head in the gill cavity. This is a twin organ. In addition, they are very gentle, so to protect them covers the top of the gill cover. But do all the gills have the same structure? Of course not. Different groups of fish it is different. For example, in Cyclostidae the gills are saccular, and in cartilaginous, for example sharks, they are lamellar. But in the largest group - teleosts - the combs are combed. They have the most complex structure. Also a very interesting fact: unlike all the others, the bony fish "breathe" through the mouth. But in Cyclostium myxin and cartilaginous rays, water comes from outside with oxygen. In the process of evolution, the respiratory organs of the fish are constantly complicated and improved. Most fish breathe oxygen dissolved in water, but there are exceptions, those that can use air.
Dog fires
Dog fishes breathe the same as all other species. But they have one interesting feature. This very ancient group of fish has not only gill but also pulmonary respiration. Once upon a time these species were widely distributed on Earth. Now there is only one detachment - corpuscle. They are found in Australia, Africa and South America. As the organs for pulmonary respiration, these fish have one or two (depending on the type) of the bladder. They are located on the esophagus from the ventral side. This allows the lungs to stay in oxygen depleted reservoirs for a long time, where other fish can not survive.
Respiratory organs of the cyclostomes
At the dawn of the appearance of fish, perhaps, the first to develop, though not the most complex, but still gills, are the cyclostomes. It's not even fish at all. Minultifs (cyclostomes) appeared much earlier and are a separate squamous group. Their respiratory organs are represented by branchial sacs. They have an endodermal origin and are the result of separation from the pharynx. How does a lamprey fish breathe with their help? She has seven paired gill sacks, each with two holes. The first is called the outer one, and the second is called the inner one, it leads into the respiratory tube. In addition, this hole can be constantly opened and closed. The respiratory tube itself was formed as a result of division of the pharynx. The upper part became digestive, and the lower part became respiratory. In most minnow the outer gill openings are united into one channel. It opens slightly beyond the last branchial sac. In the lamprey and myxine, the nasal opening is connected to the pharynx. Therefore, even when the fish buries into the sand, it can breathe. When the cyclostomes feed, the water penetrates the gill sacks not through the mouth or nasal cavity, but through the outer gill openings.
Structure of the gill body of bony fishes
Bony fishes breathe with gills. They have a complex structure. Thus, the gill apparatus consists of five branchial arches. They are in a special cavity behind the head. In order to protect the arc from mechanical damage, a hard and durable gill cover covers them from above. It grows as the fish grow in size. Gill arches on the outside have two rows of petals, which are supported by supporting cartilages. In them, the gas exchange process takes place. The artery fits the gill lobes and brings the arterial blood. Here it is enriched with oxygen and carries it to all organs and tissues. On the inside there are gill rakers. They act as a filter and protect against ingestion of food particles.
How does the fish breathe in the water?
The respiration of fish is as follows. When inhaled, it opens a wide mouth opening. In this case, the gill arches maximally move apart, and the gill cover, on the contrary, tightly presses against the head. Thus, water enters the oral opening and passes on, but does not go outside. Further, in the gill cavity oxygen is absorbed through the petals. Oxidized blood, coming to them, is saturated. Enriched with oxygen, she carries it to all the tissues of the fish. As you exhale, the mouth of the fish closes, and the gill covers rise. Thus, the water is squeezed out. In the capillaries of the petals on the gill arches, not only the gas but also the water-salt exchange occurs. In the water from the blood vessels not only carbon dioxide is released, but also ammonia and other substances that are produced in the course of metabolism. This is a detailed description of how the fish breathe underwater.
Additional respiratory organs
But like most species that live on the Earth, fish have additional respiratory organs. Of course, the gills remain the main ones. But apart from them, during the gas exchange, the skin, intestines and even special organs, such as pulmonary sacs or "labyrinth", participate. But all this is worth telling in order. Many fish species, especially those that use turbid, oxygen-depleted waters as their habitat, are very intensely dermal breathing. How does the fish breathe skin? It simply absorbs oxygen through its surface. Sometimes this breath even comes out on top. Another device is a swim bladder. It accumulates air, and the fish absorbs oxygen from it. So she can even live out of the water for a while. The same role as a swim bladder can be performed by the intestine. Labyrinth fish in the branchial cavity have a special pocket-shaped department. Its walls are densely permeated with capillaries. Gas exchange processes take place in them. It is noteworthy that labyrinth fish breathe atmospheric oxygen. They can do without water for several days. Of course, this is far from being all examples of how different species of fish surprisingly adapt to the environment. They have many more secrets, how to survive even in very difficult conditions.