Study of the haemocytic parameters of cockroaches (Periplaneta americana) post stimulation with bacterial spores

Abstract

Haemocytes and haemolymph are the major mediators of immunity in cockroaches (Periplaneta americana). The six different types of haemocytes reported are prohaemocytes, plasmatocytes, granular haemocytes, oenocytoids, spherules and adipohaemocytes. These cells have their own structural and functional uniqueness. In this study, we injected cockroaches with bacterial spores and compared the number and size of the haemocytes in control and inoculated populations. The number of viable haemocytes in the inoculated population was less than that in control. There was a significant increase in the number and size of plasmatocytes in the immunized cockroaches. The adipohaemocytes also showed increase in size in the inoculated population. Both plasmatocytes and adipohaemocytes exhibit phagocytic activity. Additionally, more production of superoxide anions in the haemocytes of inoculated cockroaches are indicative of increased phagocytosis. We also report a change in protein profile of haemolymph of the injected cockroaches. The heightened activity of few haemocytes and bio-molecules in the immunized cockroaches, hint towards an activated cellular and humoral immune response due to inoculation. Together, these findings re-establish the fact that the invertebrate immune system responds variably to antigenic challenge.