We tend to think of endothermic and exothermic animals as two sides of a coin, as if you're one or the other.

我们喜欢把内性和外性看成硬币的两面，似乎你必须是两者之一。

Which makes sense, because many large sharks today are mesothermic – they can keep their bodies a little warmer than the surrounding water temperature, which helps them stay active even in colder waters.

这很有道理，因为今天许多大型鲨鱼都是中性的——它们能够保持身体的度比周围高，这帮助它们即使在冷中也能保持活跃。