Ultrastructure of the larval midgut of Bittacus planus (Mecoptera: Bittacidae) and Neopanorpa longiprocessa (Mecoptera: Panorpidae)

Bittacidae and Panorpidae are the two largest families in Mecoptera. The larvae of Bittacidae are different from those of Panorpidae in external morphology and habits, and have an interesting habit of spraying the body surface with soil through the anus. However, it remains unknown to date whether the larval midguts are different in structure between the two families. Here the ultrastructure of the larval midguts of the hangingfly Bittacus planus Cheng and the scorpionfly Neopanorpa longiprocessa Hua & Chou were compared using light, scanning, and transmission electron microscopy. The midguts of both species are simple tubes of single layered epithelia with digestive and regenerative cells but without diverticula. The basal plasma membrane of epithelial cells exhibits infolding in B. planus, but is closely apposed to its basal lamina in N. longiprocessa. Lymph spaces are present between adjacent epithelial cells in B. planus, but are absent in N. longiprocessa. The regenerative cells are scattered among the digestive cells in B. planus, but are aggregated in N. longiprocessa. The longitudinal muscle bands are compact in B. planus, but are sparse in N. longiprocessa. The compact longitudinal muscle bands are likely associated with their soil-spraying habit in Bittacidae.

Lufenuron impact upon Anthonomus grandis Boheman (Coleoptera: Curculionidae) midgut and its reflection in gametogenesis

The insecticide Match® (lufenuron), one of the main insect growth regulators used in pest control, has been presented as a viable alternative against the boll weevil, Anthonomus grandis (Coleoptera: Curculionidae), by inhibiting chitin synthesis. Thus, this study aimed to examine whether Match® interferes in the synthesis of the peritrophic matrix, leading to changes in the midgut epithelium, resulting in nutritional deficiency and reflecting, thereby, in the gametogenesis process of A. grandis. Floral cotton buds were immersed in the insecticide solution (800μL of Match®+200mL of distilled water) and offered to the adult insects. The midguts of the insects were evaluated after 24 and 120h after feeding. The gonads were evaluated after 120h. The results showed that Match®, in both evaluation periods, induced histopathological alterations such as disorganization, vacuolization and desquamation of the midgut epithelium; histochemical modifications in the distribution patterns of carbohydrates, although without quantitative changes; and a strong decrease in protein levels. No apoptosis were observed, however, there was an increase in the number of regenerative cell nests. In the testicles, a reduction in the amount of spermatozoids and reduced carbohydrate levels were observed, but no difference in protein levels. The ovarioles presented structural disorganization of follicular cells, yolk reduction and decrease in protein levels, however, no change in carbohydrates levels was noted. Therefore, it is concluded that Match® performs histopathologic and histochemical alterations in the midgut epithelium and the gonads of A. grandis adults, reflecting in the gametogenesis process, presenting itself as a promising tool in the management of this pest on cotton crops.