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How Aquatic Animals Breathe

A great diversity of animals inhabit the aquatic environment, belonging to very diverse groups, from amphibians to crustaceans and fish. All types of aquatic animals also require oxygen to live . Since dissolved oxygen in water is less abundant than in air, these animals require specialized organs to breathe and make it possible to exchange gases with water, instead of with air as we and other beings that we do. they live out of the water.

In this AgroCorrn article we seek to shed light on the doubts that revolve around how aquatic animals breathe and we also discuss which group of these animals uses each of the different breaths.

You may also be interested in: How amphibians breathe

Cutaneous or skin respiration in aquatic animals

This respiration is typical of amphibian animals . To allow cutaneous respiration to take place , the skin must be bare, hairless, and abundantly vascular (with blood vessels).

In this type of respiration the skin acts as a membrane that filters oxygen from the water and exchanges it with the blood that is circulating through the vessels under the skin. Oxygen passes into the blood to oxygenate the body’s tissues and carbon dioxide performs the reverse path, exiting through the skin to the external environment.

A requirement for cutaneous respiration is that the skin must always be kept moist to perform the exchange. However, a drawback is that it is an inefficient type of breathing and must be complemented with another type of breathing. Among the animals with this type of respiration are amphibians such as the axolotl , frogs , toads, salamanders (semiaquatic) and newts, echinoderms such as sea urchins, sea cucumbers and starfish and annelids such as leeches and the Korean earthworm. or nereis.

In this other AgroCorrn article we will talk about what animals are amphibians and where they are found .

Branchial respiration of aquatic animals

This is the most common type of respiration among the different types of aquatic animals . The organs that allow gas exchange between the animal and the water are the gills , which extract the dissolved oxygen in the water and transfer the carbon dioxide to the environment.

The gills are vascularized organs, where the captured oxygen passes into the internal fluids of the animal, the blood or the hemolymph. Subsequently, oxygen is transported and exchanged by these fluids with tissues and cells, which need them for metabolic processes.

The gills are organs that are made up of epidermal cells and are externally covered with very fragile soft tissues. The gills are located outside the body, because as water has a higher density than air, the entrance to the internal organs is very complicated. The oxygen captured by the gills passes by diffusion into the blood. In this transport, the gas passes through a membrane to an area where it is in lower concentration and the carbon dioxide follows the reverse path.

Gill-breathing aquatic animals are the vast majority and include almost all fish, some reptiles in their early stages of development, most mollusks and crustaceans, some annelids and zoophytes.

How aquatic animals breathe with lung respiration

Although it seems incredible that there are aquatic animals that breathe through lungs, there are both freshwater and saltwater animals.

The lungs are organs that are responsible for extracting oxygen that is in the air and also releasing carbon dioxide into the environment. The lungs are highly vascular, so that oxygen passes by diffusion into the blood vessels and can oxygenate tissues and cells, and carbon dioxide follows the reverse path. Aquatic animals with this respiration spend most of their life in the water, but they require interaction with the air to obtain oxygen, so they leave the water from time to time. Here is a list of aquatic animals with lung respiration they are:


Amphibians can have all three types of respiration. It is during their adulthood when they acquire pulmonary respiration. Thus, frogs or salamanders have been able to adapt to a semi-aquatic life.


Among the reptiles with lung respiration we find sea ​​turtles , crocodiles, alligators or some aquatic snakes.


Although these animals do not live directly submerged in water, some birds such as web-footed animals (for example ducks or cormorants) have lung respiration and are also considered aquatic animals.


It is common to wonder how whales or other marine mammals breathe , since they live in water but we see them breathe air and they are mammals, like us, which can lead us to think, quite correctly, that we actually have many similarities with they.

The aquatic or marine mammals are the best known case of aquatic animals with lungs . Here we find cetaceans ( whales and dolphins), pinnipeds (seals, walruses, sea lions, wolves and bears), sirenians (such as manatees), rodents (such as beavers) and pachyderms (such as hippos).

Among the adaptations of some aquatic animals with lungs are the possession of internal cavities, where they store the necessary oxygen to pass some type in the water. Others go out and inhale seasonally.

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