Abstract:
Anopheles mosquitoes have been shown to adapt to heavy metals in their natural habitats.
In this study we explored the possibility of using Anopheles gambiae sensu stricto as bioreporters for environmental heavy metal pollution through expressions of their metalresponsive metallothionein and alpha-tubulin genes. The study was undertaken with third instar larvae after selection by cadmium, copper, or lead at LC(30) through five
successive generations. Expression levels were determined in the 5th generation by semiquantitative RT-PCR on the experimental and control populations. The data were
analyzed using one-way ANOVA. The highest metallothionein (F(3,11)=4.574, P=0.038)
and alpha-tubulin (F(3,11)=12.961, P=0.002) responses were observed in cadmiumtolerant
treatments. There was significantly higher expression of metallothionein in cadmium or copper treatments relative to the control (P=0.012), and in cadmium than in lead treatments (P=0.044). Expressions of alpha-tubulin were significantly higher in
cadmium than in control treatments (P=0.008). These results demonstrate the capacity of
An. gambiae s.s. to develop tolerance to increased levels of heavy metal challenge. The
results also confirm the potential of heavy metal-responsive genes in mosquitoes as
possible bio-indicators of heavy metal environmental pollution. How the tolerance and
expressions relate to An. gambiae s.s. fitness and vectorial capacity in the environment
remains to be elucidated.
