The digestive system of the citrus psyllid, Diaphorina citri, and the potato psyllid, Bactericera cockerelli (Hemiptera: Psyllidae)

The psyllid digestive system is under intensive study because of its role in the transmission of Candidatus Liberibacter. The digestive organs of the citrus psyllid and the potato psyllid have the same basic construction. Both have one pair of primary salivary glands, each with a digitate appendix referred to as an accessory gland. Both have a ventriculus composed of three parts, V1, V2 and V3. V1 is a sheathed filter organ consisting of the basal (afferent) and apical (efferent) lengths of the ventriculus fused together. V2 and V3 are the mesal, unsheathed lengths of the ventriculus. The ventriculus leaves the filter chamber to become V2 and V3. V3 loops around to reenter the filter chamber and fuse with the basal, afferent section. When this anatomy is compared with basic insect digestive system physiology, numerous questions arise. The primitive midgut-hindgut junction cannot be determined morphologically, and may no longer be discrete in these species. The osmoregulatory function of the filter chamber, as it is understood from model groups, does not account for the excretory products that pass through it from V3.