Are Fish Cold-blooded? If yes, then Why?

Fishes are called 'Cold Blooded' because they do not regulate their internal body temperature, so it changes with their surroundings. Fishes are cold-blooded vertebrates that live in water, breathe with gills, and have fins rather than legs.

There are 3 classes of fish:-

• Jawless fishes (lampreys and hagfishes)
• Cartilaginous fishes (sharks, skates, rays )
• Bony fishes

All three types of fish are "cold-blooded".This means that they can't control their body temperature internally. Their body temperature is similar to the temperature of their outside environment.

Characteristics of fish

• All fish are cold-blooded, which is also called ectothermic(They can't control their body temperature internally, so it changes with their surroundings).
• They do not have lungs but can breathe through their gills.
• Fins for movement.
• Swim bladders.
• Two chambered hearts.
• No eyelids.
• No external ears.

Are all fish called cold-blooded?

Not all fishes are cold-blooded. Some exceptions are Opah and Moonfish which circulate heated blood throughout its body.

Opah is equipped with specialized blood vessels that carry warm blood to its gills to rewarm the blood that cools as the fish breathes and absorbs oxygen from the water.

Some fish live in cold water. Fish living in cold climates have evolved an adaptation to keep from freezing: Antifreeze protein, arctic and Antarctic fish families have these proteins in their blood.