The animals are able to breathe underwater through the gills, specialized organs found in fish. There are reptiles - such as turtles - and mammals - such as whales or dolphins - that spend most of their time underwater, although they have to rise to the surface to take oxygen from the air.
These species have developed mechanisms of adaptation to the environment throughout their existence. Therefore, it is important to explain how these living beings function in the environment where they live.
Depending on the type of animal we will analyze how is the respiration of many of these species that manage to survive under special conditions.
Fish breathing
For the Administration for Children and Families of the Department of Health and Human Services of the United States of America, the process of respiration of fish and amphibians is defined as follows:
“Fish can live in a particular form of water. For example, a fish that lives in salt water in the ocean would not be able to live in the fresh water of a lake. Like other living things, fish breathe oxygen. Instead of getting oxygen from the air around them, they absorb oxygen from the water around them through their gills.
The gills are the respiratory organs of aquatic animals formed by sheets that protect their body and some internal organs.
They allow oxygen to be taken from the water, which enters through the mouth and the blood vessels in the gills carry oxygen into the blood. Amphibians carry out the metamorphosis process of which they also breathe through the lungs.
Now, there are differences between the forms of respiration through the lungs and gills. For example, whales and dolphins have lungs like humans, but they rise to the surface to breathe because they breathe through the nostrils located on the top of their heads.
In the case of fish, they have gills and respiration occurs when the fish opens and closes its mouth; when opening the mouth, the water enters while when closing it, it pushes the water towards the gills.
Aquatic mammals must carry out this process of constantly taking oxygen from the surface, in order to live in the environment that surrounds them. The fish take from the water - fresh or salt - the oxygen that the gills take and these transport them to the rest of their body.
Regarding the function of the internal gills of the fish, the process happens like this: when the fish breathes, it takes a bite of water at regular intervals. This moves to the sides of the throat, forcing the water through the gill openings, so that it passes over the gills on the outside.
In this way the fish can breathe continuously, using the external and internal gills periodically.
Respiration of aquatic insects
Some insects spend the early stages of their development in water. There are species that happen to live in the air.
Some examples of this type of animal are dragonflies, nymphs, and other species that are born as aquatic larvae.
Like all animals, these insects also need to convert oxygen to carbon dioxide to survive. The breathing process in this case occurs through holes that are found on the sides of their bodies, called spiracles.
The spiracles are openings in a series of tubes in the body of the insect that carry oxygen to the most important organs. In aquatic insects an adaptation has occurred in this system to be able to spend part of their life under water.
On the immersion of aquatic mammals
A fascinating point regarding the respiration of aquatic mammals is the way in which marine vertebrates adapt to the pressure existing on their bodies when they are submerged, very contrary to that of invertebrates in water.
While these animals do not breathe underwater, they are capable of holding their breath for long periods, which is a subject of study for scientists and researchers.
Obviously, the lungs and other organs involved in respiration, as well as other susceptible organs, are affected by immersion in great depths, being "crushed" under such pressures.
However, the ability to adapt to these conditions prevents lung collapse and damage to other organs, thanks to the thoracic cavity and especially. The middle ear of these marine species have a specialized physiology that protects them and gives them the ability to stay underwater for a long time.
The chest walls of marine mammals are capable of supporting complete lung collapse.
On the other hand, the specialized structures of your lungs allow the alveoli (small sacs that are part of the respiratory system and where gas exchange occurs between breathed air and blood) to collapse first, followed by the terminal airways.
These structures can also aid in the re-inflation of the lung after immersion by means of chemicals called surfactants.
With respect to the middle ear, these mammals possess cavernous sinuses specialized in this organ, which are presumed to remain submerged in blood while the immersion is taking place, thus filling the air space
It is surprising how different species are able to function in their own environments, especially with respect to the process of respiration - inhalation of oxygen and exhalation of carbon dioxide - in environments as different as air and water.
Lungs and gills are complex structures, adapted to extremely different conditions but that ultimately achieve the same goal: to provide the body with the oxygen necessary for its survival.
References
- Animals I. Fur, Fins, Feathers and More. Teacher's Guide. Recovered from eclkc.ohs.acf.hhs.gov.
- Harvey. S. (2007). Bailey Gartzet Elementary: Breathing Underwater. Recovered from: gatzertes.seattleschools.org.
- Kreitinger, L. (2013). Corell University Blog Service: Life under Water. Recovered from blogs.cornell.edu.
- Native Ecosystems. Recovered from gw.govt.nz.
- Costa, P (2007). University of California Museum of Palentology. Diving Physiology of Marine Vertebrates. Recovered from ucmp.berkeley.edu.