Ultrastructure of the haemocytes of tobacco armyworm Spodoptera litura Fab. (Lepidoptera: Noctuidae)

Ultrastructural and histochemical studies revealed the presence of five types of haemocytes in the last instar larvae of Spodoptera litura Fab., namely the prohaemocytes (PRs), plasmatocytes(PLs), granular haemocytes(GRs), spherulocytes(SPs), and oenocytoids(OEs). The prohaemocytes were found to be the smallest of all the haemocyte types, having a high nucleo-cytoplasmic ratio. The plasmatocytes were polymorphic in shape and their nucleus was either lobed or oval. The granular haemocytes were characterized by two types of electron dense granules i.e, structureless, uniformly dense bodies and membrane-bound structured granules having compactly arranged microtubules. The spherulocytes were characterized by the presence of large-sized cytoplasmic spherules, generally obscuring the nucleus. The oenocytoids revealed certain alternating and parallel hyaline and dark areas in their cytoplasm and only this haemocyte type reacted positive to dihydroxy phenyl alanine (DOPA).