With one or two exceptions, all reptiles are considered to be cold blooded as they use exothermic means, such as sunning on rocks, or shading themselves, to control their body temperature.
Cold blooded does not mean reptiles have cold blood. They are, however, referred to as “cold-blooded” animals because of how they regulate their body temperatures through a process called thermoregulation.
That the lengthy list of cold-blooded animals is dominated by reptiles and amphibians shouldn't really come as a surprise, considering that nearly all animals in these groups are ectotherms. As you go through some examples provided in this AnimalSake article, you will get a better idea as to which species are considered cold-blooded.
Most reptiles today are cold-blooded, meaning their body temperature is determined by how warm or cold their surroundings are. But, some of the modern ocean's top predators, tuna and swordfish, are “homeothermic” (aka warm-blooded), or able to keep their body temperatures at a constant temperature despite changing environmental conditions.
All the amphibians are cold blooded I.e they can't maintain a constant body temperature the reason for this is the design of their heart where both the oxygenated and deoxygenated blood gets mixed as a result they are cold blooded only mammals and birds are warm blooded as the have 4 chambered heart where the blood dosen't get mixed.
With a few exceptions, all mammals and birds are warm-blooded while all reptiles, arachnids, insects, amphibians and fish are cold-blooded. Now, what does it mean to be warm-blooded or cold-blooded? What are cold blooded animals? Cold-blooded animals’ body temperature is regulated by the environment.
Reptiles are indeed "cold blooded" animals. This means that they are unable to self regulate their body temperature. If they get too cold, they get sluggish and slow and have to lay out in the sun ...
A cold-blooded animal's level of activity depends upon the temperature of its surroundings. A reptile, for example, will increase its body temperature before hunting and is better able to escape predators when it is warm. Cold-blooded animals also need to be warm and active to find a mate and reproduce.
Not all fish are cold-blooded. In 2015, researchers with the NOAA Southwest Fisheries Science Center revealed the opah, or moonfish, as the first fully warm-blooded fish. Although not as warm as mammals and birds, the opah circulates heated blood throughout its body, giving it a competitive advantage in the cold ocean depths from 150 to 1,300 feet below the surface.
Mostly, cold-blooded animals consist of reptiles, amphibians, and some fishes, as well as bugs and even bees. Fish. Image Source. Not all fishes are cold-blooded, but only a few are known as warm-blooded ones (Opah). So a maximum species of fish such as goldfish, salmon, sharks, piranhas, etc. are considered as the cold-blooded animals.