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Effect of insecticide resistance on development, longevity and reproduction of field or laboratory selected Aedes aegypti populations.

Martins AJ, Ribeiro CD, Bellinato DF, Peixoto AA, Valle D, Lima JB - PLoS ONE (2012)

Bottom Line: In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level.In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control.Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Rio de Janeiro, Brazil.

ABSTRACT
Aedes aegypti dispersion is the major reason for the increase in dengue transmission in South America. In Brazil, control of this mosquito strongly relies on the use of pyrethroids and organophosphates against adults and larvae, respectively. In consequence, many Ae. aegypti field populations are resistant to these compounds. Resistance has a significant adaptive value in the presence of insecticide treatment. However some selected mechanisms can influence important biological processes, leading to a high fitness cost in the absence of insecticide pressure. We investigated the dynamics of insecticide resistance and its potential fitness cost in five field populations and in a lineage selected for deltamethrin resistance in the laboratory, for nine generations. For all populations the life-trait parameters investigated were larval development, sex ratio, adult longevity, relative amount of ingested blood, rate of ovipositing females, size of egglaying and eggs viability. In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level. In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control. Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost.

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Number of eggs – field populations.Number of eggs per egglaying female of Aedes aegypti F1 field population and Rockefeller. Each dot indicates the number of eggs from an individual female. Identical letters above the scatter dots mean non-significant differences according to One Way ANOVA followed by Tukey Multiple Comparison Test.
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pone-0031889-g008: Number of eggs – field populations.Number of eggs per egglaying female of Aedes aegypti F1 field population and Rockefeller. Each dot indicates the number of eggs from an individual female. Identical letters above the scatter dots mean non-significant differences according to One Way ANOVA followed by Tukey Multiple Comparison Test.

Mentions: Among the five field populations evaluated, a delay in larval development was observed only in Fortaleza mosquitoes, whose pupae formation rate differed from the Rock strain at the 5th (q = 7.994; p<0.01) and 6th days (q = 5.777, p<0.05) after larvae hatching (Figure 6). Fortaleza adults also exhibited the lowest longevity (Figure 7). Nevertheless, compared to Rock, this reduction was only evident by the 50th day after adult emergence in the case of males (q = 5.777, p<0.01, Figure 7A). This effect was more pronounced among females: differences were already noticeable on the 30th day (q = 5.726, p<0.05, Figure 7B). Similarly to the laboratory selected lineages, in no case significant differences in the sex ratio were detected (data not shown). The amount of ingested blood did not differ significantly among populations and Rockefeller (F = 1.1779, p = 0.1917), ranging from 1.8 to 2.1 times the female weight. Notwithstanding, although Rockefeller exhibited a slightly higher number of eggs compared to natural populations, significant differences were noted only between Rock and Fortaleza (mean diff. = 32.5, t = 5.3, p<0.05; Figure 8). There was no significant difference in the rate of egg hatching among populations and Rock (data not shown). The egg hatching rate was 81.5 to 94.0% respectively for Fortaleza and Rockefeller, but this difference was not significant between them (ANOVA, followed by Tukey Multiple Comparison Test, p>0.05).


Effect of insecticide resistance on development, longevity and reproduction of field or laboratory selected Aedes aegypti populations.

Martins AJ, Ribeiro CD, Bellinato DF, Peixoto AA, Valle D, Lima JB - PLoS ONE (2012)

Number of eggs – field populations.Number of eggs per egglaying female of Aedes aegypti F1 field population and Rockefeller. Each dot indicates the number of eggs from an individual female. Identical letters above the scatter dots mean non-significant differences according to One Way ANOVA followed by Tukey Multiple Comparison Test.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3303777&req=5

pone-0031889-g008: Number of eggs – field populations.Number of eggs per egglaying female of Aedes aegypti F1 field population and Rockefeller. Each dot indicates the number of eggs from an individual female. Identical letters above the scatter dots mean non-significant differences according to One Way ANOVA followed by Tukey Multiple Comparison Test.
Mentions: Among the five field populations evaluated, a delay in larval development was observed only in Fortaleza mosquitoes, whose pupae formation rate differed from the Rock strain at the 5th (q = 7.994; p<0.01) and 6th days (q = 5.777, p<0.05) after larvae hatching (Figure 6). Fortaleza adults also exhibited the lowest longevity (Figure 7). Nevertheless, compared to Rock, this reduction was only evident by the 50th day after adult emergence in the case of males (q = 5.777, p<0.01, Figure 7A). This effect was more pronounced among females: differences were already noticeable on the 30th day (q = 5.726, p<0.05, Figure 7B). Similarly to the laboratory selected lineages, in no case significant differences in the sex ratio were detected (data not shown). The amount of ingested blood did not differ significantly among populations and Rockefeller (F = 1.1779, p = 0.1917), ranging from 1.8 to 2.1 times the female weight. Notwithstanding, although Rockefeller exhibited a slightly higher number of eggs compared to natural populations, significant differences were noted only between Rock and Fortaleza (mean diff. = 32.5, t = 5.3, p<0.05; Figure 8). There was no significant difference in the rate of egg hatching among populations and Rock (data not shown). The egg hatching rate was 81.5 to 94.0% respectively for Fortaleza and Rockefeller, but this difference was not significant between them (ANOVA, followed by Tukey Multiple Comparison Test, p>0.05).

Bottom Line: In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level.In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control.Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Rio de Janeiro, Brazil.

ABSTRACT
Aedes aegypti dispersion is the major reason for the increase in dengue transmission in South America. In Brazil, control of this mosquito strongly relies on the use of pyrethroids and organophosphates against adults and larvae, respectively. In consequence, many Ae. aegypti field populations are resistant to these compounds. Resistance has a significant adaptive value in the presence of insecticide treatment. However some selected mechanisms can influence important biological processes, leading to a high fitness cost in the absence of insecticide pressure. We investigated the dynamics of insecticide resistance and its potential fitness cost in five field populations and in a lineage selected for deltamethrin resistance in the laboratory, for nine generations. For all populations the life-trait parameters investigated were larval development, sex ratio, adult longevity, relative amount of ingested blood, rate of ovipositing females, size of egglaying and eggs viability. In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level. In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control. Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost.

Show MeSH
Related in: MedlinePlus