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b"This week we're going to learn about some fish that feature warm-bloodedness! Thanks to Eilee for suggesting the moonfish, or opah.\\n\\nFurther reading:\\n\\nAre all fish cold-blooded?\\n\\nThe Opah Fish Is Warm-Blooded!\\n\\nBasking Sharks Are Partially Warm-Blooded, New Research Suggests\\nMegalodon Was Partially Warm-Blooded, New Research Shows\\nThe opah, or moonfish, looks like a pancake with fins but is an active swimmer [picture from first article linked above]:\\n\\n\\n\\nAn opah not having a good day [photo by USA NOAA Fisheries Southwest Fisheries Science Center - https://swfsc.noaa.gov/ImageGallery/Default.aspx?moid=4724, Public Domain]:\\n\\n\\n\\nShow transcript:\\nWelcome to Strange Animals Podcast. I\\u2019m your host, Kate Shaw.\\nMonths ago now, Eilee suggested we talk about the sunfish. We\\u2019re actually not going to talk about the sunfish this week, although it is on the list to cover eventually. Instead, we\\u2019re going to talk about something else in Eilee\\u2019s email. Eilee asked if there was a moonfish too, and not only is there a moonfish, it\\u2019s basically the most unique fish alive today in one particular way. It\\u2019s warm-blooded!\\nThe moonfish is also called the opah. It\\u2019s golden-orange in color with little white spots, and it\\u2019s very round and flattened side-to-side, like a pancake with orange fins. It has big golden eyes and a tiny mouth. It\\u2019s also quite large, with the biggest species growing up to 6 and a half feet long, or 2 meters. That\\u2019s a really big pancake. It lives in the ocean, sometimes diving deeply, and despite looking like a pancake, it can swim very quickly to catch squid and small fish. It also eats krill. The reason it can swim so quickly is because it has huge muscles that power its fins, and the muscles also generate a lot of heat, enough to keep its entire body at least several degrees warmer than the surrounding water. This is a warm-blooded trait, but fish are supposed to be cold-blooded.\\nThe scientific term for warm-bloodedness is endothermy. Mammals and birds are endothermic, meaning our internal body temperature stays roughly the same no matter what temperature it is outside. Cold-bloodedness, called ectothermy, means an animal\\u2019s internal body temperature fluctuates depending on the temperature outside its body. Reptiles, amphibians, fish, and invertebrates are all cold-blooded.\\nTo us as mammals, it feels like warm-bloodedness is a really good idea, but it comes at a high cost. Mammals and birds have to eat a lot more and a lot more often than cold-blooded animals do, because keeping our body temperature steady takes a whole lot of energy. An endothermic animal generates heat mainly by metabolizing food, although muscle movements like shivering and running also generate heat. An endothermic animal can be as active at night as it is during the day, and can be as active in winter as it is in summer.\\nSome otherwise cold-blooded animals can generate enough heat with muscle movements to warm parts of the body, called regional endothermy, or can generate heat with muscle movements in certain situations, called facultative endothermy. The female of some species of snake, especially some pythons, will wrap her body around her eggs and shiver, which generates enough heat to keep the eggs warm. Bumblebees can also shiver to warm their bodies enough to allow them to fly in cold weather. At least some species of sea turtle, including the green sea turtle and the leatherback, generates enough heat in its muscles while swimming that it\\u2019s able to migrate long distances in very cold water. Some scientists think all marine reptiles may be regional endotherms to some degree.\\nSome fish demonstrate regional endothermy too. So far, 35 species of fish are known to be partially warm-blooded, including some species of tunas, sharks, and billfish. Scientists originally thought that only predatory fish needed the extra boost of speed and endurance that endothermy provides, but then they discovered the basking shark is regionally endot..."