MECANISMOS DA AÇÃO LARVICIDA DO DIFLUBENZURON SOBRE Aedes aegypti EVIDENCIADOS PELAS ALTERAÇÕES ULTRAESTRUTURAIS

Abstract

Mechanisms of the larvicidal effect of diflubenzuron on Aedes aegypti larvae, as evidenced by ultrastructural changesDengue is a viral disease transmitted by Aedes aegypti in over 100 countries in the intertropical band in the world and the main forms of control are antivectorial actions. In this paper, ultrastructural changes caused by diflubenzuron (DFB) are presented. The experiments were performed with 3 rd instar larvae of Ae. aegypti with DFB at concentrations of 0.1 and 1 µg/mL. After 24h of exposure, larvae were collected, fixed, dehydrated, embedded, cut, contrasted with uranyl acetate and 3% lead citrate and examined under the electron microscope. Ultrastructural alterations caused by the diflubenzuron inhibitory activity were observed in the cuticle and in the midgut of Ae. aegypti larvae treated with 0.1 and 1 µg/mL, for 24 hours. The alterations observed by scanning microscopy included higher number of bristles, which were thinner and longer than the controls and exhibited a coiling pattern in the intersegmental grooves. Transmission electron microscopy analysis revealed that the epicuticle almost came entirely off the new epicuticle and had no points of reinforcements commonly found in the control. The midgut cells of the larvae treated with diflubenzuron presented a spongy skeleton and in the ultrathin sections, the cells showed intense vacuolation and damage, however with secretion vesicles present and mitochondria preserved. These studies indicate that the diflubenzuron can also act in the midgut cells, being a promising product for use in Ae. aegypti control. This study showed that the DFB interferes with the process of ecdysis, prevents the release of the old cuticle that accumulates in the intersegmental spaces and strangle the segmental portions in a successive and cumulative process, blocked the changes, causing the death of the larva. It also acts destroying the midgut cells.

Baccharis reticularia DC. and Limonene Nanoemulsions: Promising Larvicidal Agents for Aedes aegypti (Diptera: Culicidae) Control

“…The observed morphological alterations in treated A. aegypti larvae are in accordance with previous works [ 25 ] and may affect larvae development and motility contributing to the observed high mortality. For example, the increase in the number of sows can hamper the exoskeleton exchange process, as seen by Borges and coworkers [ 55 ]. However, other factors can contribute for larvicidal activity on mosquito larvae, such as the damage to the digestive tube which is associated to anti-feedant behavior [ 56 ].…”

Subchronic exposure to diflubenzuron causes health disorders in neotropical freshwater fish, Prochilodus lineatus

“…In fish farms, the insecticide has been intensively applied in water and fish feed (Schalch et al, ) to control ectoparasites (Schalch et al, ; Mabilia and Souza, ) and insect larvae during fish larviculture (Pelli et al, ). Recently, DFB has been used to control the Aedes aegypti mosquito, the dengue disease vector, because the adult mosquito is resistant to organophosphate, carbamate, and pyrethroid pesticides (Borges et al, ). DFB has been considered a promising insecticide for mosquito control; therefore, the insecticide is used year‐round for mosquito control in neotropical and tropical regions and is applied directly to the water.…”

Tremor essencial em guardas de endemias expostos a agrotóxicos: estudo caso-controle

“…Esse é um elemento essencial do exoesqueleto com função de proteção mecânica. Caso consiga eclodir, induz à malformação e à esterilidade nos insetos adultos 23 .…”