Histological and ultrastructural aspects of larval corpus allatum of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) treated with diflubenzuron and chromafenozide

Abstract

The present investigation was undertaken to follow the two insect growth regulators (IGRs), diflubenzuron and chromafenozide, possible effects on the histology and ultrastructure aspects of corpus allatum (CA) of 6th instar larvae of Spodoptera littoralis. Therefore, the LC50 (3 ppm of diflubenzuron and 0.1 ppm of chromafenozide) were applied to the 4th larval instar. The CA of 6th larval instar treated with LC50 of diflubenzuron appeared with rounded shape and decreased size (265.625 μm width & 331.25 μm length) and the capsular fibrous sheath (3.380 μm) also reduced. Contradictory, cellular cortex was increased in size (71.875 μm), as well as glandular cell numbers were increased, and their nuclei were lost their spheroid shape. Disturbance in cytoplasmic organelles pushed glandular cell to switch off or to be inactive. Also, damage was pronounced in the CA of the LC50- chromafenozide treated larvae. The present work investigates the high potency and efficacy of the two IGRs towards S. littoralis corpora allata.