Betta Fish Anatomy: Male vs Female, Internal & External Differences

For any betta lovers, it must be fun to know full details about their betta fish anatomy. When you know about the internal and external anatomy of your betta, you’ll understand well about their functions. Without knowing how the body parts work, you may not readily catch any abnormalities in your betta fish.

Moreover, there are some subtle differences in the anatomy of male and female betta fish. It’s pretty significant to know about the anatomical differences between male and female betta fish to make treatment a necessity.

In this article, I’ve penned down the betta fish anatomy, internal and external differences in their anatomy, and the differences between male and female betta fish anatomy.

Key Takeaways

  • Male and female betta fish have some significant differences in their external and internal anatomy.
  • The external anatomy of betta fish refers to the outer structure and organs that can be visible from the outside.
  • On the other hand, the internal anatomy of betta fish shows inner organs and systems within the betta body.

External Betta Fish Anatomy

Since external betta fish anatomy refers to the exterior features of betta fish, you might recognize many of these body parts. To have a good grasp of knowledge, let’s take a detailed look at all the outer parts of betta fish. Starting from the head backward, you can pinpoint all organs and parts of your betta fish from this article.

External (Upper) & Internal (Lower) Anatomy of Betta Fish

1. The Betta Fish Body Shape

Although the body shape of female and male betta has slight differences, these bettas have a streamlined body. Due to such a streamlined structure, the wild bettas can readily slip through open water. As a result, bettas can move effortlessly to catch their prey.

Their bony body structure makes these bettas fast-moving fish. Also, these colorful bettas are covered with scales. Under the right conditions, betta fish can grow up to 2.5-3 inches.

2. Head

The head of a betta fish looks flat and it contains two eyes on each side. In front of the head, betta fish has a mouth with tiny teeth. The large head of betta fish can be considered as the control system of the betta body.

After all, betta fish have a tiny brain inside their head. Nervous systems and labyrinth organs are arranged inside the head of betta fish. So, you can say that the head of betta fish controls all activities and behavioral patterns. It includes swimming, eating, breathing oxygen, attacking prey, etc.

chocolate color betta fish

3. Body

In the external betta fish anatomy, we can see a streamlined body of betta fish that reaches more than 2.5 inches. Like maximum fish, the body of betta fish is covered with scales except the fins. Their bodies have different colored pigmentations that make them appear gorgeously colorful betta fish.

Some bettas may have solid coloration, whereas some bettas possess two different color tones. In the wild, you will find any specifically plain-colored betta fish. But, people can get betta fish with the body of any vibrant shades by breeding in captivity.

However, the body of betta fish is highly sensitive. These soft-bodied betta fish are susceptible to injuries. If you notice horizontal lines in the bodies of your female betta fish, it’ll be a sign of stress or threats to your betta. But, horizontal lines in the body of betta fry are developmental marks.

4. Scales

The very first thing that you might notice at the exterior sight of a betta fish’s body is its scales. These scales resemble ‘plated armor’ that fulfills the purposes of protection and locomotion. The prominent betta fish scales look metallic and shiny. 

These scales are mainly thin and transparent plates covered with an extra mucus layer. They are arranged in beautiful layers with darker edges. Depending on the types of bettas, these fighting fish may have varieties of colored scales. Sometimes, health issues, diet, or age play a prominent role in changing the color of betta fish scales.

However, there’s a misconception that betta fish might shed their scales. But, it’s not a fact for the cases of healthy and happy betta fish.

5. Mouth: What Type Of Mouth Does A Betta Fish Have?

You might be wondering the reason behind the grumpy face of your colorful betta fish. The reason is specially featured an upturned mouth. Such a superior mouth helps betta fish catch prey smoothly from the water’s surface.

In addition, you might know that betta fish often come up to the surface to breathe oxygen. Along with surface-feeding, an upturned mouth aids betta fish to consume oxygen. Due to such unique anatomical features, male betta fish can take part in their reproductive action by making bubble nests. 

With the help of their superior mouth and saliva, male betta fish tend to attract female betta fish by creating bubble nests. Besides, these bubble nests will protect the eggs laid by female betta which will help betta fish have their offspring.

To carry the legacy of the name, these Siamese fighting fish use their sharp teeth to attack their predators or prey. Inside the mouth of betta fish, you can notice the lower jaw full of sharp and tiny teeth. The powerful action of the jaw compared with the body size makes the betta’s jaw power more powerful than other fish’s jaws.

But, you need not worry about your fingers. These tiny teeth can’t pierce human skin.

tiny vs 3 months old betta fish
Owner: Jenna Marder Grenier

6. Eyes

After the mouth, the next exterior organs are the eyes. Betta fish have two eyes that fit perfectly into the eye sockets of your Betta fish’s skull. These protruding eyes have black iris.

Another cool thing about Betta’s eyes is their perfect color vision. After all, the eyes of these bettas have diurnal retinas with far more cons than rods. Hence, these colorful bettas do not have trouble seeing highly contrasted colors.

In addition, Betta can detect shapes pretty well. That’s why your betta fish can readily locate its prey or food wherever you place them in the aquarium. Also, you might notice their visible reactions when these bettas recognize their owners during feeding or playing time.

Due to their good eyesight, these Siamese fighting fish can see full coloration and position during their fighting moments. Otherwise, these Bettas may not be able to flare at their reflection. But, Betta fish are near-sighted. Because of being short-sighted, Betta fish can possess acute effective vision up to 12-14 inches away.

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Besides, betta eyes do not have eyelids. People might wonder whether betta fish can blink. But, these bettas can not blink like humans.

In the cases of humans, our eyes are structured in such a way as to combine a single image. But, betta fish have eyes on each side of their head that prevent them from perceiving the depth of any target image. That happens due to having rods in their retinas.

If you ever wear night-vision goggles, you may know how Betta eyes work. Unlike human eyes, Betta’s eyes can look simultaneously in different directions. It causes Bettas to have a wider visual area. Instead of focusing on a single image, Betta fish can capture different images on both eyes at a time.

7. Nares

According to medical terms, the openings of the nostrils of betta fish are known as nares. Although it may seem odd, betta fish also have nostrils. If you look closely, you’ll find a pair of tiny apertures on each side of the head of betta fish. These are known as nostrils or nares.

Although humans use their nostrils for breathing, betta fish have gills for that purpose. Instead of serving as a respiratory organ, nares work as sensory organs for betta fish.

The four nares of betta fish act like sensory organs that help bettas take smell. When you leave any food in the betta tank water, it releases a chemical that triggers the specialized sense of smell.

Firstly, water passes through the front nostrils of betta fish. After that, it reaches through the nasal sac to the rear nostril. When the chemicals pass through water and hit the nasal sac, these betta fish can sense the scent.

That’s why betta fish can readily sense the fluctuations of salinity and temperature of the water. Another interesting fact about betta nares is osmoreception. This process is the ability of betta fish to detect the concentration of ions in the water.

With the help of nares, betta fish can locate the presence of predators, prey, or their foods. These nostrils help these bettas find their mates by detecting chemicals. These bettas communicate and find their partners with the help of released pheromones and amino acids.

turquoise betta fish
Owner: Gemma Barham

8. Hard Fin Ray

The hard fin rays of betta fish are used for maneuvering and propulsion. Generally, betta fin rays have 7 or 9 branches. Some betta species display 32 beams in their caudal fins. The age of betta fish, its diet, and its maintenance play a significant role in the number and sizes of fin rays.

9. Operculum

You might know that gills are one of the most sensitive organs of betta fish. Since gills are fragile and soft-structured organs, these gills require protection to remain stable in constant contact with water.

To protect these gills, the betta fish body has a unique formation named the operculum. The operculum is a bony flap that works as a shield for the fragile gills of betta fish. These bony flaps are rectangular or trapezoidal. The inner shape of the operculum is slightly concave. Also, the operculum of betta is divided into four divisions.

It serves as a protective covering of betta fish gills. These bony plates open and close to control the water passage through the gills. In this way, the operculum aids betta fish to breathe when they’re not swimming. To help the respiratory process of betta fish, the operculum ensures only one direction of water circulation through the gills.

Because of establishing one flow direction, the operculum prevents the exit of water from the betta body. There’s also a membrane behind the gill plate cover of betta fish which is referred to as opercular membrane.

10. Gills

Like all other fish, betta fish have also a respiratory organ named gills. It is the aquatic lungs of betta fish.

There are mainly two types of gills in fish which are external gills and internal gills. The external gills are located on the side of the betta fish head. If you have a look at the internal gills, the inside of healthy gills should always be red and pink colored.

These gills have a unique formation to extract oxygen from water. In the same way, gills help betta fish release the carbon dioxide from outside the body.

For this, gills have many vascularized extensions and blood vessels. When betta fish opens its mouth, the water passes through the gills. Afterward, the blood in the capillaries extracts the dissolved oxygen from the water.

You might know that betta fish are popular labyrinth fish due to their special ability to take in oxygen directly from the air. That’s why you can see betta jumping out of the water or sticking their head out of the water’s surface.

Because of the presence of gills, betta fish can also absorb oxygen from the water intake through their mouth that passes through the gills. That’s why betta fish do not have to solely rely on the air to breathe oxygen. Since betta fish tend to live in low-oxygenated water areas in the wild, gills play a significant role in kicking in such an environment.

Owner: Lisa Matson

11. Ventral Fin

Depending on betta variants, there are different styled, shaped, and sized ventral fins. Some betta fish may also not have any ventral fins which are known as pelvic fins. These ventral fins are located right behind the gills of the underside body of betta fish. However, this position may not remain constant in all species of betta variants.

These ventral fins are typically smaller than other fins. Generally, male betta fish tend to have longer ventral fins than female betta fish. Although the color of the ventral fins does not affect much on its cost, the pair of ventral fins take after the non-dominant color of the betta.

The ventral fins play a crucial role in keeping balance amidst the water. Your betta fish will readily ascend or descend into the water of the tank with the help of ventral fins. These fins aid betta fish in turning in the water. Also, the primary functions of ventral fins are to assist betta fish swimming and stopping in the water.

12. Dorsal Fin

Because of its location at the top of the body, dorsal fins are also known as top fins. Betta dorsal fins tend to be pretty large. It mainly consists of several branches. But, the sizes, shapes, and coloration of dorsal fins may vary according to the breeds of betta fish.

By following a certain trajectory, dorsal fins assist betta fish balance in the water. Otherwise, your betta fish would struggle to have proper balance to swim in a straight line. So, these fins keep betra fish stable against rolling.

Another function of the dorsal fins is to aid betta fish in turning suddenly. These fins play a significant role for betta fish to hunt their prey successfully.

13. Pectoral Fin

Another special fin of betta fish are pectoral fins that are located behind the gill opening. These pairs of pectoral fins can be found on each side of the betta fish. The pectoral fins assist betta fish to slow down.

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Also, these juxtaposed fins help bettas control depth, steer, and maneuver. In addition, the asymmetrical strokes of pectoral fins assist the betta to turn or move in the desired direction.

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14. Anal Fin

From the exterior anatomy, you can locate the anal fins readily between the pelvic fins and anal fins. It’s one of the largest fins of betta fish body. Different shapes of anal fins are found running down the betta’s body.

Anal fins are positioned right the opposite of dorsal fins. So, you can say that betta fish have anal fins at their underside, beside the anus. Like dorsal fins, anal fins help betta fish stabilize in the water. Also, these large fins aid betta fish to keep balance and steer.

15. Caudal Peduncle

The caudal peduncle is a joining of the caudal fin or tail to the body,  where you can locate strong swimming muscles. It’s a narrow part between the end of the anal fin and the base of the caudal fin.

The function of the caudal peduncle is to work like a ‘motor’ that provides a lateral force to move in heave. Otherwise, you may say that the caudal peduncle is the propeller of a betta fish.

16. Caudal Fin

Betta fish can readily catch anybody’s attention due to their fancy tail fin which is also known as the caudal fin. In the exterior anatomy of betta fish, you can pinpoint the caudal fin of your betta at the end of its caudal peduncle. Depending on the breed type, various betta fish has splendid flowing caudal fins of different shape and sizes.

However, the anatomy of the caudal fin differs from wild to captived betta. The large and flowy structure of the caudal fin may slow down betta fish in the wild. As a result, these wild bettas might become prey to their predators. On the other hand, the selectively bred betta fish tend to have bright and flowing tails for commercial purposes.

It is the only fin that remains connected to the vertebral column of betta fish. The caudal fin helps betta balance and lift. The caudal fin or tail of a betta fish generates propulsive forces that allow betta fish to swim in the water. Also, it creates locomotion for steady swimming in the water.

So, you can say that caudal fins provide the push or power to swim through the water. In addition, this caudal fin or tail gives the sudden burst of speed that helps betta fish move forward. It also works as a rudder for sudden turning.

External (Upper) & Internal (Lower) Anatomy of Betta Fish

Internal Betta Fish Anatomy

Several types of significant organs can’t be seen from outside. If you know the internal anatomy of betta fish, you can readily detect any malfunctions of bettas’ organs. To know about the performance of all organs, let’s see the location, sizes, shapes, and functions of these organs from this internal anatomy.

1. Esophagus

The esophagus is a short and expandable internal organ of betta fish that helps betta swallow large objects. It is a muscular tube that receives the food from the mouth. Since the muscles of the esophagus consist of several layers, foods can be readily broken down in this tube. It works by the principle of crushing the foods.

This muscular tube plays a significant role in contributing nutrition to the body of betta fish. After ingesting the food through the mouth, the esophagus breaks down the food and passes the water, food, and air to various organs of betta fish.

There’s a ring muscle at the end of the esophagus that lets the broken foods pass into the stomach. Moreover, it ensures a one-direction process by contracting the muscle. As a result, processed foods can’t escape from the stomach back to the esophagus.

2. Gill Arch

No matter what species are your bettas, all bettas have gill arches to support the gill. The gill-arch is a complex vertebrate organ that connects between gill rakers and gill filaments. It has a curved structure, which provides a cover for gills and blood vessels. There are several paired filaments in each gill arch.

Generally, betta fish have four-gill arches on their body. You can locate two pairs of gill arches on each side of the gills of betta fish. The primary work of gill arches is to pass the air through the gill cavity from the esophagus.

Due to its curved shape, gill arches provide a large surface area that helps betta intake large amounts of oxygen. Another function of gill arches is to facilitate the movement of gills for a smooth respiratory process.

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3. Labyrinth

Since betta fish need to survive in stagnant water in the wild, their body evolves to absorb oxygen in a different way. Although betta fish breathe with the help of oxygen, another supplemental breathing organ of betta is a labyrinth. This unique organ helps betta fish thrive in the water area of low oxygen saturation. You can also compare it to our lungs.

Because of having a labyrinth, betta fish need not solely depend on gills for oxygen uptake. You can locate the labyrinth organ in a chamber above the gills supported with blood vessels. When betta fish inhale oxygen through the mouth, the labyrinth absorbs the oxygen into the bloodstream.

Since the labyrinth develops with the age of betta fish, its shape and size vary with time. Because of being labyrinth fish, betta fish need to use their labyrinth and gills for breathing. That’s why these bettas are required to come up to the surface to gulp air.

4. Liver

While learning about the internal anatomy of betta fish, you might find similarities in several organs between you and your betta. The liver is one of them that is centrally located in the cranial region. The primary purpose of the liver is to support the digestion and storage within the betta body.

The size and shape of the liver may vary according to the gender, age, and health of betta fish. The liver assists in the production of necessary biochemicals to digest the foods. Also, it works for detoxification, protein synthesis, glucose and lipid metabolism.

The most significant function of the betta liver is to secrete enzymes. These enzymes tend to process the food in the stomach. Further, this enzyme or bile passes through the intestine to help digestion. The stored wastes in bile pass out through the feces of betta fish.

5. Kidney

In the internal anatomy of betta fish, you’ll find one of the most vital organs of betta that works as a filter. This natural filtration system of betta fish is a kidney that extracts the impurities from the bloodstream. It is a small, soft, reddish-brown elongated structure. 

Due to having a mesonephric kidney, the shape of the kidney does not evolve with the age of betta fish. Regarding body weight, the kidney size is comparatively larger than other other organs. In general, the kidney is located ventrally to the vertebral column covered by coelomic epithelium.

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This extraction organ helps the betta body maintain higher salt concentration in the bloodstream than the water. If you notice the signs of dropsy in your betta fish, an underlying cause may be kidney failure.

6. Swim Bladder

The swim bladder is a gas-filled buoyancy organ that is formed behind the pharynx from a part of the digestive tube of betta fish. It’s an endodermal outgrowth.

This internal organ is located in the abdominal cavity along the spine in the rear body. Although it’s an internal organ, you can see the protruding swim bladder near the caudal peduncle from the exterior look.

Generally, the swim bladder contains oxygen which aids betta fish to stay buoyant. However, there can be the presence of other gasses too. In short, a swim bladder is a buoyancy organ. 

Because of having a swim bladder, a betta fish can sink and swim in a deep layer of water. Similarly, this buoyancy organ helps betta rise in the water surface rapidly. Since the swim bladder helps the betta keep its buoyancy, your betta need not swim constantly to stay in a certain place.

As a result, this buoyant organ saves the energy of your betta fish. Other functions of the swim bladder are to aid in respiration, pressure fluctuations, etc.

7. Testes

In the case of male betta fish, these bettas have paired testes. Testes are located between the swim bladder and intestine of male betta fish. This male reproductive organ is white.

The size of the testes ranges from 1.11 to 2.16 mm. These elongated organs are formed of somatic cells and germ cells. The prime function of the testes of male bettas is to produce sperm.

8. Bladder

A urinary bladder is an extension part of the urinary duct of betta fish. You might have already known that the kidney works as the natural filtration system in the body of betta fish. The urinary bladder stores the wastes filtered from the kidney.

9. Stomach

Betta fish stomach is located slightly behind the gills right below the face. In the internal anatomy of betta fish, you can find a tiny stomach, which is as small as the size of betta eyes. Betta fish stomach is a curved pouch with a glandular lining and muscular wall known as the vital digestive tract.

The primary function of a betta stomach is to store the food. Also, the work of protein digestion initiates in the stomach. The betta fish stomach secretes several digestive enzymes that help foods get digested in this organ. Besides, the produced enzymes aid in breaking down materials like bacteria. 

Since the betta stomach creates an acidic environment, this organ can kill unwanted microorganisms. The muscular wall of the stomach contracts at regular intervals. Further, the betta stomach churns the foods and passes them down the intestine. So, a betta stomach assists in gastrointestinal motility.

cute betta fish close up
Owner: Michelle Smith

10. Intestine

Although the primary purpose of the intestine is to digest foods, this vital organ absorbs the essential nutrients from the foods. After breaking down in the stomach, the food passes through the intestines. Intestines systematically break down the remaining foods and extract the water. For this purpose, the intestine contains several types of mucous and digestive juice.

Another significant work of the intestine is to absorb the electrolytes, protein, and vitamins from the food. Afterward, this intestine uses these products of nutrient digestion as the fuel of the betta body. Finally, the indigestible materials will pass through the feces of betta fish. In addition, the kidney of betta fish takes part in the excretion process.

11. Heart: Do Betta Fish Have A Heart?

Yes, indeed. Like all fish, betta fish also have a heart, consisting of four chambers. These chambers are an atrium, a ventricle, a sinus venosus, and a bulbus arteriosus. The betta fish heart draws in the deoxygenated blood from all body parts.

Afterward, this organ pumps oxygenated blood through blood vessels all over the body. The function of blood circulation can not be done without this vital internal organ of betta fish. The heart also regulates the blood pressure of betta fish.

The gills of betta fish work in coordination with the betta heart simultaneously. When the heart performs the circulation of oxygenated blood, the waste carbon dioxide passes through the gills into the water.

12. Anus

There is no surprise that betta fish also poop. After digesting the foods, the betta intestine absorbs the nutrients. The remaining matter comes from betta fish as their poop through the anus.

Also, the undigested foods pass to the exterior environment through this organ. It is located at the underside of betta fish behind the ventral fins.

13. Betta Fish Bones

You might know that betta fish are popular bony fish. Irrespective of species, all betta fish have a skeleton and bones. In general, betta fish tend to have 83 bones.

male vs female betta fish anatomy
Male vs Female Betta Fish Anatomy

Male Betta Fish Anatomy Vs Female Betta Fish Anatomy

For any beginners, it’s pretty hard to distinguish between male and female betta fish. Although male and female betta look almost similar, they share some anatomical differences. Knowing a vast knowledge of internal and external differences will let you choose and provide a comfortable life for your betta fish.

External Anatomical Differences Between Male & Female Bettas

CategoriesMale Betta FishFemale Betta Fish
Body shapeMale betta fish tend to have thicker bodies compared with female betta bodies.Female betta fish tend to have thinner bodies.
SizeThe size of a male betta fish ranges from 2.5 to 3 inches long, excluding fins and tails.Female betta fish are a bit shorter than the male betta fish. An adult female betta can reach up to 2-2.5 inches.
Fins and tailsMale betta fish showcase more external beauty than female betta fish. These male bettas have longer anal fins, dorsal fins, and tails.Female betta fish do not have large and flowy fins.
ColorationMale betta fish tend to have bright coloration and hues that make them visually appealing.Female betta fish tend to have duller coloration than male betta fish.
StripesMale betta fish do not have any stripes on their body.Female betta fish show several stripes on their bodies.
Bubble nestIn general, male betta fish blow a bubble nest that is made of saliva.Female betta fish do not make bubble nests.

Internal Anatomical Differences Between Male & Female Bettas

CategoriesMale Betta FishFemale Betta Fish
Membrane below gill plateMale bettas have larger beards that are basically a membrane below the gill plate. While showing aggression, male bettas tend to flare these beards.Female betta fish have also a membrane below their gill plate. However, the beards of female bettas are not very visible due to their shorter sizes.
Ovipositor tubeMale betta fish may show an egg spot that can make it harder to distinguish the gender. But, male betta fish do not have any ovipositor like female bettas.Female betta fish tend to have an ovipositor tube or egg spot near the base of ventral fins. These female bettas release eggs from this ovipositor tube during mating.
TestesMale betta fish have testes.Female betta fish do not have any testes that are basically male reproductive organs. 

Frequently Asked Questions (FAQ’s)

Do Betta Fish Have Brains?

Like every living creature, betta fish also have a brain. Otherwise, these betta fish would not be able to use their intelligence for catching prey, competing for food, recognizing owners, etc. The formation of the betta fish brain may not be as similar of a human brain. That’s why betta fish aren’t able to do complex thinking.

Where Are Betta Fish Ears?

Although you may not find any external ears in betta fish, these bettas have tiny holes in the sides of their heads. Such hearing structure is found in the internal anatomy of betta fish. That’s why betta fish can hear the presence of predators, any dropping foods, and other noises. Sometimes, loud noises may cause shock to your betta fish.

How Big Is A Betta Fish Stomach?

A betta fish’s stomach may not exceed the size of its eye. If your betta fish has a bloated belly, it may suffer from constipation. Due to the tint size of the stomach, the experts suggest not to overfeed the betta fish.

Where Do Bettas Poop Come From?

You might not realize that your betta fish poop in the tank without noticing its feces at the bottom. Betta fish have an anus located in front of their anal fin.

Before You Go…

I hope you have got a detailed overview of the internal and external anatomy of betta fish and the anatomical differences between male and female bettas. Since you have shown some interest in the anatomy of betta fish, you might be curious to know about betta fish genetics. To check out the science behind breeding colorful bettas, you can take a quick look at the following article.

Betta Fish Genetics 101: Science Behind Breeding Colorful Bettas

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Muntaseer Rahman

About Author

Hello, I’m Muntaseer Rahman, the owner of I’m passionate about aquarium pets like shrimps, snails, crabs, and crayfish. I’ve created this website to share my expertise and help you provide better care for these amazing pets.


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