In more advanced lesions, pseudomembrane formation was common. Formation of a pseudomembrane is considered to be an attempt to protect the cuticular epithelium from ulceration (Smolowitz, Bullis & Abt 1992). In other crustaceans, the transformed cells responsible for pseudomembrane formation appear to originate from an influx of semigranulocytes or agranulocytes (Johannson & So¨derhall 1989). Blue crab haemocytes in the haemolymph have been subdivided into three major morphological types; namely, hyaline, small granular and large granular haemocytes (Clare & Lumb 1994). However, inflammation in blue crabs has not been well studied and, thus, the definition of histological haemocyte equivalents requires further study.