Betta anatomy

The total body length of a betta, including fins, is usually between 5 and 7 cm. Body shape is 'fusiform', which means streamlined, tapered toward each end.

Seen from the front, a betta's head has a rather bulldoggish look. The mouth is downturned, with the opening facing upward, an adaptation to allow bettas to feed, take air and blow bubbles on the surface of the water. The lower jaw is powerful, and a betta's teeth are sharp -- they can deliver quite a nip! The gill plates (opercula) are located on either side of the head, behind the eyes. These protect the delicate gills while controlling the flow of water over the gill surface. The opercular membrane lies underneath, and is normally concealed by, the gill plates. (See sidebar).

Bettas have three unpaired fins:

• dorsal fin
  
• caudal fin (tail)
  
• anal (or pelvic) fin
  

and two sets of paired fins:

• pectoral fins (behind the gills)
  
• ventral fins (on the belly)
  

The male's fins are longer and fuller than those of the female, and continue to grow throughout the male's life. For more information about the shape of the caudal and other fins, see Tail Types.

   

People and fish share many similarities in internal organs. Such organs as the brain, stomach, liver, kidneys and gonads are present in both, and have much the same functions. Other organs appear in different forms in different organisms; for example, the lungs in humans and the gills and labyrinth organ in bettas are very different but both provide the same basic function of respiration. Finally, some organs (such as the swim bladder) are simply not present in man.

In addition to gills, which allow fish to extract oxygen from water, bettas and other other labyrinth fish have an accessory respiratory organ, the labyrinth, which enables them to take air directly from the water's surface. The labyrinth is located in a cavity in the betta's head, alongside and above the gills. The organ consists of a series of folded tissues, through which venous blood flows. The fish gulps air at the surface of the water, holding it in the cavity where the labyrinth organ extracts oxygen by gaseous exchange directly into the bloodstream. The fish then gulps water, flushing the labyrinth organ to allow the release of carbon dioxide.(See sidebar).

The kidneys filter liquid waste materials from the blood; these wastes are then passed out of the body. The kidney is also extremely important in regulating water and salt concentrations within the fish’s body. The stomach and intestines break down food and absorb nutrients. Primarily carnivorous fish such as bettas have fairly short intestines because such food is easy to chemically break down and digest. The liver has a number of functions. It assists in digestion by secreting enzymes that break down fats, and also serves as a storage area for fats and carbohydrates. The liver also is important in the destruction of old blood cells and in maintaining proper blood chemistry, as well as playing a role in nitrogen (waste) excretion. The swim bladder is a hollow, gas-filled balance organ that allows the betta to conserve energy by maintaining neutral buoyancy in water, and helps it to move up and down in the water column. The swim bladder inflates as the fish moves up towards the surface, and deflates to help the fish swim down in to deeper water. The swim bladder can absorb or release tiny amounts of gas into the bloodstream as it expands or contracts. (See sidebar).

In the male, the testes produce sperm. In the female, the ovaries produce eggs (ova). When spawning, eggs are released through the female's ovipositor, which is visible as a white dot, the 'egg spot', on the belly, just behind the ventral fins. In a female in breeding condition, the ovaries are sac-like and full of eggs. They may be visible as triangular yellowish patches on either side of the belly, above the egg spot.

   

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© Vicki Parslow Stafford 2005 (unless otherwise stated)
Ipswich Qld AUSTRALIA