What distinct morphological feature separates *Cherax quadricarinatus* from *C. destructor*?

A distinct ridge on the carapace margin

Even within the same genus (*Cherax*), different species must possess sufficient morphological or genetic differences to warrant separate classification, which is critical for species management. The Redclaw crayfish, *Cherax quadricarinatus*, is differentiated from the Common Yabby (*C. destructor*) by a specific external feature: a distinct ridge located on the carapace margin. This feature is so prominent that it contributes to its specific name, 'quadricarinatus,' meaning 'four-ridged.' This subtle yet definitive morphological distinction allows researchers and managers to distinguish between the two species, which is vital for biosecurity assessments, especially since the Redclaw is known to become invasive outside its native range.