Male adults possess a green fluorescent protein (GFP, 27 kDa) in their flexible abdomen that serves as the ultimate light emitter in the bioluminescence reaction of the animal.

The protein is made up of 238 amino acid residues in a single polypeptide chain and produces a greenish fluorescence (λmax = 508 nm) when irradiated with long ultraviolet light.

It is likely that crayfish have never been widespread in Northumberland National Park as their preferred habitat of calcareous burns, rivers, and lakes is very limited.

A fine preserved example of a thirteen inch specimen can be seen in the lounge bar of the "Jingling Gate" public house near Westerhope.

It is likely that crayfish have never been widespread in Northumberland National Park as their preferred habitat of calcareous burns, rivers, and lakes is very limited.