Observations on morphological, physiological, and behavioural changes induced by protozoan infections in certain storage insect pests.

Entomopathogenic protozoans are, to a large extent, host specific, and through acute or chronic infections they negatively alter host reproductive fitness, metabolism, immune response, juvenile hormonal balance, and host development. Hence, these entomopathogens are well-suited to reduce populations of stored product insect pests. The first step towards achieving successful suppression, natural or applied, of storage insect pest populations is the detection for these entomopathogenic protozoans in their habitats. Therefore, a preliminary survey of naturally occurring protozoan infections in stored-grain insect pests was carried out across some Governorates in Lower and Upper Egypt. The protozoan-natural mortality rates among the subject insect pests were recorded. Based on morphological characteristics, particularly spore or oocyst morphology, five entomopathogenic protozoans were taxonomically identified, at the genus level (i.e., four apicomplexans, Adelina sp., Farinocystis sp., Mattesia sp., and Gregarina sp., as well as one microsporidian or fungal pathogen, Nosema sp.). Observations on the morpho-pathological, physio-pathological, and behavioural changes induced by protozoan infections in beetles of Cryptolestes turcicus, Rhyzopertha dominica, Tribolium castaneum, and moths of Plodia interpunctella were recorded, as well. Among the interesting findings, a behavioural abnormality was induced by Nosema infection in P. interpunctella moths; viz., the complete failure of copulated pairs to be separated after copulation (i.e., frequent occurrence of ca., 66.70-73.70 %). Additionally, an increased abundance, by ca., 2.40-fold, of the total protein content has been quantified in Adelina-infected or Farinocystis-infected T. castaneum beetles compared to the uninfected beetles. The pathological changes observed in this study may provide new insights into the interaction between the subject entomopathogenic protozoans and their insect hosts.