1. Earthworms
Earthworms, also known as "earth dragons," prefer warm environments and are sensitive to both cold and heat. They hibernate at 0-5℃, cease growth above 32℃, and die above 40℃. The suitable temperature range is 15-30℃, with the optimal breeding temperature being 20-25℃. Therefore, to achieve good breeding results, the optimal breeding environment of 20-25℃ should be maintained year-round. Earthworms breathe through their skin, so their bodies must be kept moist. Water accounts for more than 75% of their body weight, and preventing water loss is crucial for their survival. Therefore, the moisture content of the feed should ideally be maintained at around 70%.
2. Pig
There are three main reasons why pigs are sensitive to heat: First, pigs are homeothermic animals, meaning their body temperature remains constant; it cannot be too high or too low. High body temperature prevents heat dissipation, leading to increased organ activity and eventual death from exhaustion. Conversely, low body temperature often results in insufficient nutrient supply, also causing organ failure and death. Maintaining a constant body temperature is crucial for pigs' survival. Second, pigs have abundant adipose tissue, especially subcutaneous fat; however, larger pigs generally have significantly more subcutaneous fat than smaller pigs. Fat is an excellent insulating material, making it difficult for the pig's body heat to dissipate. However, fat also serves specific functions for pigs, and their thickness should not be reduced simply because they are sensitive to heat. Third, pigs have underdeveloped sweat glands and do not dissipate heat through sweating like humans.
3. Dog
Because dogs' sweat glands are not as evenly distributed as humans' and their ability to sweat is weaker, they don't use sweat to cool down. Their only way to cool down is through their tongues. Therefore, short-nosed dogs are more susceptible to heat in summer because their shorter noses cause them to dissipate heat more slowly. In summer, due to the high temperatures and their thick coats, dogs cannot quickly dissipate heat through sweating, making them very sensitive to heat.
4. Starfish
Starfish are among the most structurally and physiologically representative of echinoderms. They have flattened bodies, mostly exhibiting pentaradial symmetry, with indistinct boundaries between the body disc and arms. When alive, their mouth faces downwards and their aboral surface upwards. The ventral sides of their arms have ambulatory grooves from which tube feet extend. The endoskeleton's plates are connected by connective tissue, making it flexible and malleable. Starfish are poikilothermic (cold-blooded) animals, lacking an internal mechanism for regulating body temperature. They can only adjust their temperature according to their surrounding environment. A temperature exceeding 35 degrees Celsius in their central body disc severely threatens their lives.
5. Polar ice worms
Polar ice worms belong to the phylum Annelida, class Hirudinea, order Oligochaeta, suborder Tuberculata, family Lymnaeidae. They are known as the only organisms on Earth that cannot be killed by freezing, possessing characteristics that scientists envision for extraterrestrial life. Scientists believe that this rare cold-resistant constitution of ice worms proves that similar cold-resistant organisms may exist on other planets. Polar ice worms are not only resistant to freezing but also to starvation. Scientists once placed several ice worms in a refrigerator for research. Two years later, the ice worms, without food or water, still stubbornly survived in the cold storage. However, polar ice worms also have a fatal flaw—they are sensitive to heat. As long as the temperature exceeds 4°C, polar ice worms begin to "melt," turning into a viscous substance.
6. South American chinchilla
Chinchillas belong to the order Rodentia, suborder Hystricomorpha, family Chinchillidae. Native to the Andes Mountains of South America, they have an average lifespan of 10-20 years. Because they resemble Totoro from Hayao Miyazaki's film *Totoro*, they are affectionately known as "Totoro" in Hong Kong. Extant varieties include short-tailed and long-tailed chinchillas. Long-tailed chinchillas are commonly kept as pets. They are herbivores, primarily fed chinchilla food and timothy hay, and require frequent teeth cleaning. Temperatures exceeding 26 degrees Celsius greatly increase the risk of heatstroke in chinchillas, although it's not 100% guaranteed. Many novice chinchilla owners, seeing high temperatures but no heatstroke in their chinchillas, become complacent, ultimately leading to their chinchillas' death from heatstroke.
7. Polar bear
The polar bear, a species of bear in the genus Ursus of the family Ursidae, is the largest land carnivore in the world. Also known as the white bear, its skin is black, but due to its translucent fur, it usually appears white, although it can also be yellow or other colors. It is a massive and ferocious animal. Polar bears have eyesight and hearing comparable to humans, but their sense of smell is extremely sensitive, seven times that of dogs. They can run at speeds up to 60 km/h, 1.5 times faster than the world's fastest 100-meter sprinter. Polar bears are capable of surviving harsh environments, primarily inhabiting the ice-covered waters near the Arctic Ocean. Studies show that when temperatures exceed 21.1°C, polar bears exhibit severe heat stress symptoms.
