Challenging environments can help create some of the most marvelous evolutionary solutions. Two examples: The stoplight loosejaw and the marlin.

The Stoplight Loosejaw is a small, deep sea dragonfish that has an “invisible” red headlight that hides his presence from possible predators. The marlin, a huge fish that can clock up to 80 km/h (50 mph), has “heat-producing tissue beneath the brain and adjacent to the eyes” that helps their brains and eyes work faster. Steve Palumbi, co-author of Extreme Life of the Sea, explains these two wonders in this Cal Academy video.

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