Abstract
Population control of the dengue vector mosquito, Aedes aegypti, is difficult due to many reasons, one being the development of resistance to neurotoxic insecticides employed. The biosynthesis of chitin, a major constituent of insect cuticle, is a novel target for population control. Novaluron is a benzoylphenylurea (BPU) that acts as a chitin synthesis inhibitor, already used against mosquitoes. However, information regarding BPU effects on immature mosquito stages and physiological parameters related with mosquito larval development are scarce. A set of physiological parameters were recorded in control developing larvae and novaluron was administered continuously to Ae. aegypti larvae, since early third instar. Larval instar period duration was recorded from third instar until pupation. Chitin content was measured during third and fourth instars. Fourth instars were processed histochemically at the mesothorax region, stained with hematoxylin and eosin (HE) for assessment of internal tissues, and labeled with WGA-FITC to reveal chitinized structures. In control larvae: i) there is a chitin content increase during both third and fourth instars where late third instars contain more chitin than early fourth instars; ii) thoracic organs and a continuous cuticle, closely associated with the underlying epidermis were observed; iii) chitin was continuously present throughout integument cuticle. Novaluron treatment inhibited adult emergence, induced immature mortality, altered adult sex ratio and caused delay in larval development. Moreover, novaluron: i) significantly affected chitin content during larval development; ii) induced a discontinuous and altered cuticle in some regions while epidermis was often thinner or missing; iii) rendered chitin cuticle presence discontinuous and less evident. In both control and novaluron larvae, chitin was present in the peritrophic matrix. This study showed quantitatively and qualitatively evidences of novaluron effects on Ae. aegypti larval development. To our knowledge, this is the first report describing histological alterations produced by a BPU in immature vector mosquitoes.
Highlights
The mosquito Aedes aegypti, an important vector of arboviruses such as dengue fever, urban yellow fever and chikungunya [1,2] is a holometabolous insect possessing a life cycle with four stages: egg, four larval instars, pupa and adult
A direct relationship between novaluron concentration and earlier mortality of immature specimens was observed: the proportion of dead larvae increased on EI99 compared with EI50 (Figure 1A)
When the novaluron EI50 was used (Figure 2B), larvae ecdysis to L4 was initiated on the 3rd day but only on the 7th day it was completed
Summary
The mosquito Aedes aegypti, an important vector of arboviruses such as dengue fever, urban yellow fever and chikungunya [1,2] is a holometabolous insect possessing a life cycle with four stages: egg, four larval instars, pupa and adult. Being fundamentally aquatic, this mosquito reaches the terrestrial environment only as an adult [3]. Chitin is present in the integumental cuticle and peritrophic matrix of larvae and adults and in the serosal cuticle of eggs [7,8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
