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Human beings carry out gas exchange to breathe with the help of the lungs, nostrils, trachea and bronchi. However, in the case of fish and other aquatic animals, such as some mollusks, amphibians, etc., they must have specialized organs to obtain the limited oxygen present in the aquatic environment. These organs are called gills or gills.
In this Green Ecologist article we will see +40 animals that breathe through gills. Did you know them all?
What is gill or gill respiration
The gill respiration It is the exchange of gases (oxygen and carbon dioxide) through specialized organs called gills (or more colloquially, gills). They are organs that are located behind the head in aquatic animals. Its appearance is that of small sheets arranged one on top of the other and with multiple blood vessels in their structure.
The function of gill respiration begins when the animal absorbs the oxygen from waterEither thanks to the current of water or by an operculum, which is a harder fin that protects the gills and guides the water towards them. Once taken, the oxygen passes into the blood or another internal fluid such as hemolymph. From these fluids, oxygen is transported to the different tissues and organs that require it for metabolism and cellular respiration in the cell's mitochondria.
Once this oxygen has been used and after cellular respiration, carbon dioxide is generated, which is a toxic gas for animals and must be expelled by the body into the environment. Carbon dioxide follows the reverse path, that is, it also passes into internal fluids and goes to the lungs where it diffuses and is expelled by them.
Types of gills: external and internal
In the animals that possess them, there are two types of gills. According to research, the origin of both types is the same, but over time they evolved in different ways according to the needs of the animal. For example, aquatic animals with slow metabolism are able to breathe with the external parts of their body and diffuse oxygen into internal fluids. These are the two types that exist:
External gills
According to scientists, the external gills are the oldest evolutionarily and the most common in aquatic animals. These gills are formed by small plates or appendages on the upper part of the body. This type of gills also has certain disadvantages, such as being easier to injure, being more conspicuous by predators and making movement in the sea more difficult.
The external gills are the majority within the marine invertebrates such as mollusks, annelids, aquatic larvae, etc. and among some aquatic or semi-aquatic vertebrates (amphibians) such as newts and salamanders.
Internal gills
These types of gills are more complex than the external ones. They are located internally in the animal, specifically under the pharyngeal fissures, which are the orifices that communicate the interior of the animal's body with the external environment. In turn, the gills are traversed by blood vessels, oxygenating the body's blood, which is then directed to the body's tissues and organs. In addition, with this type of gill there is a ventilation system that protects the organs of respiration and provides them with greater aerodynamics and utility.
These types of gills are the majority within marine vertebrates, such as fish.
Examples of animals that breathe through gills
After knowing all the above information, you will ask yourself what are the animals that breathe through gills. Some examples of them are the following:
Frog
Like other amphibians, the frog has gill respiration during its larval and tadpole stage in water. Upon reaching adulthood, the gills disappear and is replaced by cutaneous and pulmonary respiration.
Octopus
This cephalopod mollusk has gill respiration and three hearts. Two of which are responsible for directing the blood necessary for gas exchange towards the gills, and the third for pumping oxygenated blood towards the tissues.
Clam
It has two pairs of gills, which are formed by ciliated blades. In addition, they help osmotic regulation, digestion and excretion.
Shark
All species, from the white shark to the whale shark, have gills of cartilaginous tissue that open and close to allow the passage of water and gas exchange.
Stingray
Like the shark, it has cartilaginous gill structures, which are located in the lower part of the body, close to the base of its dorsal fins.
Sea hare
It is an elongated and muscular mollusk of up to 20 cm. Their gills are located only on the right side of the head.
Lungfish
Both the Australian and the African have a double respiratory system with lungs and gills, which allows them to live out of the water for seasons. Learn more about them with this article on What fish breathe out of water.
Axolotl
The axolotl or axolotl is an amphibian, a relative of the tiger salamander, endemic to the Mexican territory. It has three pairs of gills that come out from the base of its head and are directed backwards.
Other species of animals that breathe through gills
To finish, we leave an extensive list with more names of animals that breathe through gills:
- Tintorera
- Whale shark
- Hammerhead shark
- Stingray shark
- Eels
- Sturgeon
- Tuna
- Cod
- Sardine
- Golden
- Tilapia
- Betta fish
- Guppy
- Lion fish
- Saw fish
- Napoleon fish
- Sunfish
- Bighead fish
- Discus fish
- Scalar fish
- Angel fish
- Swordfish
- Blowfish
- Rainbow Fish
- Stone fish
- Piranha
- Catfish or catfish
- Tents
- American mudfish or scaly salamander fish
- Prawns
- Prawns
- Crabs
- Lobsters
- Sea snails
- Sea urchins
- Seahorses
- Sea slugs
- Common sea cucumbers
- Japanese sea cucumbers
- Tadpoles
If you liked this article, we also recommend reading this other one about 20 rare marine animals in danger of extinction.
If you want to read more articles similar to +40 animals that breathe through gills, we recommend that you enter our category of Animal Curiosities.
