Crabs are known to have superb chemosensory capabilities, walking upstream towards tantalizing chemical cues to locate food and mates, despite turbulence in the water. These detection abilities are particularly important for the mud crab; its ability to “smell” its main predator – the blue crab – is a matter of life or death. The canny crabs hide themselves away whenever one of its predatory cousins is in the vicinity - but what is it that makes the muddy invertebrates act so... spinelessly? A team from the Georgia Institute of Technology decided to wade in and find out.

“We suspected that the crabs were responding to the presence of predators by sensing chemicals that were being transmitted through the water column – however, little was known about the molecular cues involved,” says Julia Kubanek, one of the researchers (1). “We then discovered that when the mud crabs are exposed to the urine of blue crabs, we get the same hiding and hunkering down response that mud crabs exhibit when there is a whole, live blue crab nearby.”