The Living Clock: Fiddler Crab's Timekeeper of the Ocean

When is the fiddler crab the darkest according to the article?

Is the fiddler crab really keeping time or just responding to sunlight?

Answer

When the tide is low where the crab was born

The fiddler crab, living far out in the ocean, showcases a fascinating ability to indicate the time of day through the color of its skin. In the daytime, the crab's skin appears dark, while at night, it turns pale. These color changes align with the regular 24-hour rhythm of day and night.

Scientists were intrigued by this phenomenon and conducted an experiment to determine if the crab was truly keeping time or simply responding to sunlight. To test this, they kept the crabs in a dark room for several months. Surprisingly, the crab's skin continued to change color hour by hour, even without exposure to sunlight. Additionally, they found that there was a particular time of day when the skin was exceptionally dark. Strangely, this darkest skin color event did not occur at the same time every day; it was consistently 50 minutes later than the previous day.

This unique observation led scientists to a crucial discovery - the fiddler crab follows another rhythm: the rhythm of the tides. The moment when the skin is darkest coincides with low tide at the beach where the crab originated. It's a remarkable synchronization between the crab's biology and its environment, demonstrating the intricate connection between nature's rhythms and the behavior of living organisms.