Sublethal Concentration of Pyriproxyfen Reduces Testicular Connective Tissue Thickness in Euschistus heros Fabr. (Hemiptera: Pentatomidae)

The aim of this study was to determine the effect of the insecticide pyriproxyfen (Tiger™ 100 CE), juvenile hormone analogue, when applied in a sublethal LC30 concentration (0.668 mL a. i. L-1), on the morphological and morphometric parameters of external and internal connective tissue (CT) of the Neotropical-brown stink bug Euschistus heros testicles. The insecticide was applied on nymphs from the 4th instar using a Potter tower with a working pressure of 82.73 kPa (12 lb pol-²) and 1 mL of the emulsion per replicate. A completely randomized experimental design was used, consisting of two treatments (control and pyriproxyfen-treated), five repetitions, and 10 adults of E. heros per experimental unit. The insects were maintained under controlled conditions until the emergence of adults. After 48 h of emergence of adults, the testicles were collected, fixed, and processed for morphological and morphometric analyses. A change was observed in the collagen fibers of the CT of treated insects when compared with those of controls. It was also observed that both types of CT (dense irregular and loose) over the internal tunic of the treated insect were thinner than those in control insects. The analysis showed that pyriproxyfen significantly reduced the external and internal CT width and the conformation of its fibers in all the observed regions when compared with the controls; this may affect the production of the three different types of sperm present in this species.