External anatomy of betta splendens


CAUDAL PEDUNCLE Narrow portion of the fish's body to wich the caudal (tail) fin attaches.
RAYS (fins)

Bony or cartilaginous dermal rods that form the skeleton/support system of the fish's fins

  • Like masts to a ship's sails

Not labelled on the diagram, the slime coat is the mucousy coating on the fish's body. It serves as a barrier between the fish and bacteria or other pathogens in the water. 

  • Handling/netting the fish can remove/disturb the slimecoat, leaving the fish vulnerable
  • Fish should never be touched for this reason, and netting should be avoided at all costs
WEBBING (fins)

The thin, delicate membrane suspended between the rays which makes up the fish's fins

  • Like the sails of a ship

Internal anatomy of betta splendens


SWIM BLADDER An internal, gas-filled, sac-like organ that allows the fish to regulate its buoyancy, maintaining a specific depth in the water without having to expend energy swimming. It also helps to stabilize the fish in an upright position in the water because, due to its relatively higher (dorsal) position in the body, it places the fish's centre of mass below it's centre of volume (as though the fish is weighted on the bottom).