WHEN HUMANS SNIFF in order to smell something, we draw a quick puff of air into our nostrils and over chemoreceptors in our nasal cavity. But octopuses, butterflies, and other animals don’t have noses like ours. Instead, they’ve evolved other, sometimes bizarre ways of sensing the world around them.
For instance, if you were to look closely at an Oregon shore crab (Hemigrapsus oregonensis), you wouldn’t see anything resembling a nose. But that doesn’t mean the creatures have no sense of smell.
“Smelling is really important to most animals, and crabs are no different,” saidLindsay Waldrop, a postdoctoral researcher in biology at the University of North Carolina at Chapel Hill.
Toothbrush for a Nose
“We sniff with our sinuses, and crabs actually do the same thing,” said Waldrop, “only they use an external hair array that looks like a really dense toothbrush.”
These toothbrushes are located on antennae near the animal’s mouth. When the crab wants to take a sniff, it waves these arms through the water.
Quick downstrokes open the bristles, allowing water and odor molecules to swish between them. Slower upward strokes close the bristles and trap scents against chemosensory cells in the hairs to give the crab a whiff of what’s nearby.
In a paper published in the Royal Society’s journal Interface, Waldrop explained that crabs use their bristly sense organs to find food in murky environments, track down mates, and avoid becoming someone else’s lunch.
The article was published first on the National Geographic. Continue reading…