Genotoxic and mutagenic effects of methyl ether dillapiole on the development of Aedes aegypti (Diptera: Culicidae)

Dillapiole, extracted from Piper aduncum essential oil and its derivatives, has been shown to be a potential alternative to the control of Aedes aegypti, which has become resistant to synthetic insecticides. Methyl ether dillapiole (MED) and temephos (TM) were compared to complement the data on the genotoxicity and developmental changes of Ae. aegypti. Over four generations (G₁ -G₄ ), third stage larvae were treated with MED at 60, 80 and 100 μg/mL and TM at 0.002, 0.005 and 0.007 μg/mL for 4 h. Adult females were separated to estimate oviposition and hatching rates, and total egg length. Over the four generations, a significant reduction was recorded in oviposition and hatching rates, and in mean egg length (Tukey, P < 0.05), compared with the negative control (NC). Cytological slide preparations were done from adult oocytes and larval neuroblasts. The cumulative effects of genotoxic (bridges, budding and nuclear fragmentation) and mutagenic (micronucleus and chromosomal breakage) damage was observed in the neuroblasts and oocytes of exposed mosquitoes. Developmental changes and damage to the genome of MED-treated Ae. aegypti were greater than those caused by TM. Further studies should focus on understanding the effects of the MED molecule on Ae. aegypti.

Potential control of Aedes aegypti (Diptera: Culicidae) with Piper aduncum L. (Piperaceae) extracts demonstrated by chromosomal biomarkers and toxic effects on interphase nuclei

Dillapiol, a phenylpropanoid isolate from essential oils of leaves of Piper aduncum (Piperaceae), has insecticidal, fungicidal and antimicrobial activities. The insecticidal activity of dillapiol was tested in vivo on the larvae and pupae of Aedes aegypti, the mosquito vector of dengue. Specifically, the effect of dillapiol on the formation of micronuclei and chromosome aberrations was analyzed. Dillapiol treatments comprised two concentrations of 200 and 400 micro dissolved in well water, and a pure well water control used to rear four generations of mosquitoes. Micronuclei occurred in mitotic diploid and tetraploid chromosomes of larvae; nuclear abnormalities also occurred in interphase, metaphase, telophase, and single nucleus cells of pupae. Mortality, oviposition, chromosome breakage, and anaphase bridges were significantly greater in the extract treatments than in controls. The genotoxic effects of dillapiol described here suggest that this natural product may be a useful alternative for the control of A. aegypti.

Cytogenetic study of Anopheles albitarsis (Diptera: Culicidae) by C-banding and in situ hybridization

The C-banding pattern and the size and location of the nucleolar organizer regions (NORs) are described for the first time in Brazilian populations of Anopheles (Nyssorhynchus) albitarsis sensu lato. C-banding revealed variation in the size of the centromeric heterochromatic blocks in autosomal chromosomes and in the acrocentric (X) and puntiform (Y) sex chromosomes. Fluorescence in situ hybridization showed that the NORs were located in the pericentromeric region of the sex (XX/XY) chromosomes and that this coincided with the number and location of centromeric constitutive heterochromatin blocks previously revealed by C-banding. The NORs varied in size among the homologues of the three populations. These findings of the populations studied support the hypothesis that the stability of NORs in the A. albitarsis complex is characterized by the presence of clustered and conserved sites in a unique pair of chromosomes.

Ecologic observations on anopheline vectors of malaria in the Brazilian Amazon

Human intervention in the Brazilian Amazon region promotes contacts between humans and vectors that may favor the propagation of anopheline mosquitoes and the spread of malaria in the absence of planning and infrastructure to control this disease. Vector ecology studies were carried out to determine the risk areas. These data should help in designing appropriate malaria control measures. Data from 14 different regions are reported. Vectors are able to adapt to different environments, which made it necessary to study each area. The parameters studied were Anopheles breeding sites, species distribution, incidence, feeding preferences, hours of maximum activity of adult mosquitoes, seasonality, resting places, and the presence of Plasmodium. Species complexes were also studied. Anopheles darlingi may be responsible for maintaining malaria in human populations in this region. A reduction in the population density of A. darlingi in a particular geographic area can sometimes cause the disappearance of malaria. This species feeds at night but has a peak of activity at the beginning of the evening and another at dawn. Other species are mainly crepuscular and all anophelines demonstrated pronounced exophilia. The timing of feeding activities was found to vary in areas altered by human intervention and also depended on the time of the year and climatic conditions. The larvae were more abundant in the rivers with a less acidic pH and rural areas showed the highest larval index.