A nationwide hunt for giant crayfish has turned up a record-breaking specimen in Tennessee, along with a puzzle about how large these freshwater crustaceans can actually grow.
The search, which spanned North America, found that crayfish appear to run into a biological ceiling on size. Scientists suspect the limit may stem from the properties of their muscles, which might not support much larger bodies.
The Tennessee find surpasses previous records, but the broader pattern suggests that even with ample habitat, crayfish may be constrained by their own physiology. The discovery raises questions about what sets the maximum size for these animals.