Fish gills are a vital organ for aquatic life, allowing them to breathe underwater and extract oxygen from the water. They are incredibly complex organs that come in various types, structures and functions, depending on the species of fish.
In this article, we will discuss the different types of fish gills, their structure and how they work to provide oxygen to fish.
We will also explore why some types of fish gills are better adapted to their environment than others.
Popular Articles
What Is A Gill?
Fish gills are adapted for aquatic respiration, meaning they can extract oxygen dissolved in water and eliminate carbon dioxide from the body.
Fish gill is an organ in fish, located at the side of the head that helps them to breathe and extract oxygen from their aquatic environment.
So what size a gill and How many gills are there in a fish?
A gill equates to four ounces. The number of gills on a fish depends on its species; some such as sharks possess five pairs while other smaller fish such as minnows may have three or four pairs.
Fish Gill Anatomy & Structure
The gills of a fish are the organs that allow fish to breathe in water. A typical fish gill is made up of 3 parts. These three basic components are,
- Gill Arch
- Gill Filament
- Gill Lamellae
1. Gill Arches | Branchial Arch
These are bony or cartilaginous structures that support the gill filaments. They are usually located on either side of the fish’s head that support the gill structure.
Gill Rakers
Gill rakers are bony or cartilaginous structures that are found on the gill arches of fish. These are small, finger-like projections that protrude from the gill arches.
These fairly stiff, tooth-like processes present in upper limb and lower limb. These racker have anterior and posterior portion.
Why Do Fish Need Gill Rakers | Functions of Gill Rakers
In filter feeding fishes, they are used to filter food particles and other debris out of the water as it flows over the gills. The bony projection sieve the food particles.
As the fish swims with its mouth open, water flows over the gills and through the gill rakers. Any food particles or other debris in the water are caught by the gill rakers and are either trapped between the rakers or are moved towards the fish’s mouth, where they can be ingested.
These gill rackers not play any role in gas exchange. The number and length of this comb like structure vary species to species due to species specific feeding strategies.
2. Gill Filaments (Primary Gill Lamellae) | Gill Plate
These are thin, hair-like structures that protrude from the gill arches. They are responsible for exchanging oxygen and carbon dioxide with the water. Gill filaments also called as primary lamellae.
3. Gill Lamellae (Secondary Gill Lamellae)
Gill lamellae are thin, flattened structures that are found on the gills of many aquatic animals, including fish and some crustaceans.
They are arranged in a series of stacked plates or sheets, and they are used to exchange gases with the surrounding water.
Each gill lamella is lined with tiny blood vessels called capillaries, which are surrounded by a thin layer of water.
As water flows over the gills, oxygen diffuses across the thin layer of water and into the blood vessels, while carbon dioxide diffuses out of the blood vessels and into the water.
The surface area of the gill lamellae is greatly increased by the presence of many folds and creases, which allows the animal to extract a large amount of oxygen from the water.
The efficiency of this process is further enhanced by the presence of specialized cells called gill cells or chromatophores, which contain pigments that help to extract oxygen from the water.
Other important parts of fish gill are,
Gill Slits
Gill slits are small openings found on the sides of the head of some aquatic animals, including fish, sharks, skates, and rays. These openings allow water to be drawn into the mouth and over the gills, which are located within the body cavity.
Gill slits are also known as branchial slits or pharyngeal slits. They are found in the pharyngeal region of the neck, which is the area behind the head and in front of the gills.
Operculum| Gill Cover
The operculum is a bony structure that covers and protects the gills in most species of fish. It is composed of two plates, known as the opercula, that are located on either side of the head, behind the eyes.
The opercula can be opened and closed to control the flow of water over the gills, which helps the fish regulate its respiration.
Operculum Cavity
It can be opened and closed to regulate the flow of water over the gills. Inside the operculum is the opercular cavity, which contains the gills.
In addition to serving as a respiratory organ, the operculum also helps to protect the gills from damage and parasites.
It also plays a role in the fish’s ability to swim and maneuver, as the opercula can be used to generate thrust and change direction.
Types of Gill
On the basis of appearance gills are two type;
- External gill
- Internal gill
| Features | External Gill | Internal Gill |
| Position | Outside the body | Inside the body |
| Branches | This gills have branches | This gills don’t have branches |
| Origin | Ectodermal in origin | Endodermal in origin |
| Examples | Amphibians such as Salamander, larval amphibians | Fishes |
Working Mechanism of Fish Gill | How Does Fish Gills Work
Each gill is composed of filaments arranged in a protective framework of cartilage.
Blood vessels carry oxygenated blood through the capillary-like walls of these filaments which then transfer the oxygen into the bloodstream.
At the same time, carbon dioxide is expelled from red blood cells into tiny air bubbles found between capillaries within each filament before being released from the fish’s body.
So what are two methods of gill ventilation that fishes use?
Fish use two main methods of gill ventilation to extract oxygen from the water: buccal pumping and ram ventilation.
1. Buccal Pumping
This is a method of gill ventilation that is used by many species of fish. It involves the fish opening and closing its mouth to draw water over the gills.
As the water flows over the gills, oxygen diffuses from the water into the blood vessels, where it is then carried to the rest of the body.
Buccal pumping is used by many species of fish, including bony fish, cartilaginous fish, and some amphibians.
2. Ram Ventilation
This is a method of gill ventilation that is used by some species of fish, such as salmon and trout.
It involves the fish swimming forward with its mouth open, drawing water over the gills as it goes.
As the water flows over the gills, oxygen diffuses from the water into the blood vessels, where it is then carried to the rest of the body.
Ram ventilation is used by some species of fish that are active swimmers and need a constant supply of oxygen to support their high metabolism.
Functions of Fish Gills
The main functions of fish gills are:
Oxygen Uptake
Fish gills are highly vascularized, meaning they have a large network of blood vessels, which allows them to exchange oxygen and other gases with the water.
Carbon Dioxide Removal
Fish gills also help remove carbon dioxide and other waste products from the blood, which is important for maintaining the proper balance of gases in the body.
pH Regulation
The gills are also involved in regulating the pH of the blood. Fish must maintain a specific pH range in order to function properly, and the gills help to maintain this balance.
Electrolyte Balance
The gills are also involved in maintaining the balance of electrolytes, such as sodium and potassium, in the body.
Osmoregulation
The gills are important in osmoregulation, which is the process of regulating the balance of water and electrolytes in the body.
Fish gills help to maintain the proper balance of water and electrolytes in the body, which is essential for the fish’s overall health.
FAQs
Can you touch a fishes gills?
It is generally not recommended to touch a fish’s gills. The gills are delicate organs that are used for respiration, and handling them can cause damage or stress to the fish. In addition, some fish have sensitive skin and can be easily distressed by being handled.
If it is necessary to handle a fish, it is generally best to gently hold it by the body or base of the tail, rather than by the gills. This will minimize the risk of damaging the gills or causing stress to the fish.
If you need to examine a fish’s gills, it is generally best to do so in a controlled environment, such as in a tank or pond, rather than attempting to handle the fish directly. This will allow you to observe the gills without causing any harm to the fish.
Do humans have gill slits?
No, humans do not have gill slits. Gill slits are openings in the sides of the neck that are found in some aquatic animals, including fish and some amphibians.
Human embryos do have a series of folds in the neck region that resemble gill slits, but these folds do not develop into functional gills. Instead, they give rise to other structures such as the larynx, trachea, and thyroid gland.
Humans and other terrestrial animals breathe using lungs or other specialized respiratory organs, rather than using gills like fish and other aquatic animals do.
What is gill flukes in fish?
Gill flukes are parasitic flatworms that infect the gills of fish. They can cause a variety of health problems in infected fish, including breathing difficulties, reduced appetite, and weight loss. In severe cases, gill flukes can even lead to the death of the fish.
Gill flukes are transmitted from one fish to another through the water or through intermediate hosts such as snails.
Once inside the fish, the flukes attach themselves to the gills and feed on blood and other tissue. They can reproduce rapidly, and a single fish can be infected with hundreds or even thousands of flukes.
To prevent gill flukes and other parasites, it is important to practice good hygiene when caring for fish. This includes regular water changes, using a high-quality filter, and avoiding overcrowding in the tank.
If gill flukes are suspected, it is important to seek the advice of a veterinarian or other qualified fish health professional.
Can a fish have both lungs and gills?
No, fish do not have both lungs and gills. Fish are aquatic animals that breathe using gills, which are specialized organs that are adapted for extracting oxygen from water.
Fish do not have lungs like terrestrial animals do. Lungs are organs that are adapted for breathing air, and they are not found in fish or other aquatic animals.
Some fish, such as lungfish and mudskippers, do have a primitive lung-like structure that they use to help them control their buoyancy and swim more efficiently. However, these structures are not used for respiration like lungs are in terrestrial animals.
Can a human get gills?
It is not possible for humans to naturally develop gills like fish have. Gills are specialized organs that are adapted for extracting oxygen from water, and they are not found in terrestrial animals such as humans.
Why do humans not have gills?
Humans and other terrestrial animals rely on lungs or other specialized respiratory organs to breathe air.
That being said, there have been attempts to create artificial gills or gill-like devices that could allow humans to extract oxygen from water.
These organ typically use a chemical process to extract oxygen from the water, rather than using gills like fish do. However, these devices are still in the experimental stage and are not yet ready for widespread use.
What is the difference between gill rakers and gill filaments?
Gill rakers and gill filaments are two different structures found in the gills of fish. Both play a role in the process of respiration, but they have different functions.
Gill rakers are bony or cartilaginous structures that are found on the gill arches of fish. They are used to filter food particles and other debris out of the water as it flows over the gills. Gill rakers are found in most species of fish and are used to help the fish feed.
Gill filaments, on the other hand, are thin, thread-like structures that are found inside the gills. They are lined with tiny blood vessels, and it is through these blood vessels that oxygen and other gases are exchanged between the water and the fish’s bloodstream. Gill filaments are found in most species of fish and are a critical part of the fish’s respiratory system.
In summary, gill rakers are used to filter food particles from the water, while gill filaments are used to exchange oxygen and other gases with the water.
Internal Gills vs External Gills
Fish do not have external gills. Gills are internal organs that are located inside the operculum, which is a bony structure that covers and protects the gills in most species of fish.
Can fish gills breathe air?
Fish gills are specialized organs that are adapted for extracting oxygen from water, not air.
Fish rely on their gills to extract oxygen from the water and to release carbon dioxide and other waste products.
How are gills different from lungs?
Gills and lungs are two essential organs used by animals to allow them to breathe. Although these two organs perform the same basic function, they do so in very different ways.
Gills are found in aquatic organisms such as fish, amphibians, crustaceans, and mollusks. They are thin sheets of tissue containing blood vessels that take oxygen from the water around them into the bloodstream. Gills also take carbon dioxide out of the organism’s body into the environment around it.
Lungs on the other hand exist in terrestrial species such as mammals, birds, reptiles and some insects. Lungs have a dense network of air sacs that fill with air when we breathe in through our mouth or nose.
References
- Wilson, J. M., & Laurent, P. (2002). Fish gill morphology: inside out. Journal of experimental Zoology, 293(3), 192-213.
- Dutta, H. M., & Datta-Mushi, J. S. (1996). Fish morphology. CRC press.
- Dineshbabu, A. P., Sasikumar, G., Rohit, P., Thomas, S., Rajesh, K. M., & Zacharia, P. U. (2013). Methodologies for studying finfish and shellfish biology, CMFRI-NICRA publication No. 2, Central Marine Fisheries Research Institute, Kochi. 91 p.
