Limits...
Egg hatching, larval movement and larval survival of the malaria vector Anopheles gambiae in desiccating habitats.

Koenraadt CJ, Paaijmans KP, Githeko AK, Knols BG, Takken W - Malar. J. (2003)

Bottom Line: However, proportions of larvae reaching the site decreased rapidly with increasing distance.Fourth-instar larvae survived significantly longer and we estimated that the maximum survival time was 113 hrs.In addition, the results suggest that, for larval vector control methods to be effective, habitats should remain drained for at least 5 days to kill all larvae (e.g. in rice fields) and habitats that recently dried up should be treated as well, if larvicidal agents are applied.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Entomology, Department of Plant Sciences, Wageningen University, The Netherlands. sander.koenraadt@wur.nl

ABSTRACT

Background: Although the effects of rainfall on the population dynamics of the malaria vector Anopheles gambiae have been studied in great detail, the effects of dry periods on its survival remain less clear.

Methods: The effects of drying conditions were simulated by creating desiccated habitats, which consisted of trays filled with damp soil. Experiments were performed in these trays to (i) test the ability of An. gambiae sensu stricto eggs to hatch on damp soil and for larvae to reach an artificial breeding site at different distances of the site of hatching and (ii) to record survival of the four larval stages of An. gambiae s.s. when placed on damp soil.

Results: Eggs of An. gambiae s.s. hatched on damp soil and emerging larvae were capable of covering a distance of up to 10 cm to reach surface water enabling further development. However, proportions of larvae reaching the site decreased rapidly with increasing distance. First, second and third-instar larvae survived on damp soil for an estimated period of 64, 65 and 69 hrs, respectively. Fourth-instar larvae survived significantly longer and we estimated that the maximum survival time was 113 hrs.

Conclusion: Short-term survival of aquatic stages of An. gambiae on wet soil may be important and adaptive when considering the transient nature of breeding sites of this species in sub-Saharan Africa. In addition, the results suggest that, for larval vector control methods to be effective, habitats should remain drained for at least 5 days to kill all larvae (e.g. in rice fields) and habitats that recently dried up should be treated as well, if larvicidal agents are applied.

Show MeSH

Related in: MedlinePlus

Observed and expected proportions of larvae in the simulated breeding sites, placed during the egg stage at different distances from the site. Different letters indicate significant differences (P <0.05, Tukey HSD) between the observed proportions at the different distances. Significant differences (P <0.05, paired t-test) between observed and expected proportion of a distance are indicated by '*'; n.s. = not significant
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC183857&req=5

Figure 2: Observed and expected proportions of larvae in the simulated breeding sites, placed during the egg stage at different distances from the site. Different letters indicate significant differences (P <0.05, Tukey HSD) between the observed proportions at the different distances. Significant differences (P <0.05, paired t-test) between observed and expected proportion of a distance are indicated by '*'; n.s. = not significant

Mentions: The proportion of newly emerged larvae that reached the site differed significantly between distances (ANOVA, P < 0.001; Figure 2). Eighty-five percent of the eggs that were placed directly in the water, i.e. the control treatment, hatched within 3 days. A significantly lower proportion of larvae was recovered from the site, when eggs had been placed at the edge of the water surface (Tukey HSD; P < 0.001). At 2, 5 and 10 cm again a significantly lower proportion of larvae was recovered in the site, but no differences in proportions were observed between these three distances (Tukey HSD, P > 0.05).


Egg hatching, larval movement and larval survival of the malaria vector Anopheles gambiae in desiccating habitats.

Koenraadt CJ, Paaijmans KP, Githeko AK, Knols BG, Takken W - Malar. J. (2003)

Observed and expected proportions of larvae in the simulated breeding sites, placed during the egg stage at different distances from the site. Different letters indicate significant differences (P <0.05, Tukey HSD) between the observed proportions at the different distances. Significant differences (P <0.05, paired t-test) between observed and expected proportion of a distance are indicated by '*'; n.s. = not significant
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC183857&req=5

Figure 2: Observed and expected proportions of larvae in the simulated breeding sites, placed during the egg stage at different distances from the site. Different letters indicate significant differences (P <0.05, Tukey HSD) between the observed proportions at the different distances. Significant differences (P <0.05, paired t-test) between observed and expected proportion of a distance are indicated by '*'; n.s. = not significant
Mentions: The proportion of newly emerged larvae that reached the site differed significantly between distances (ANOVA, P < 0.001; Figure 2). Eighty-five percent of the eggs that were placed directly in the water, i.e. the control treatment, hatched within 3 days. A significantly lower proportion of larvae was recovered from the site, when eggs had been placed at the edge of the water surface (Tukey HSD; P < 0.001). At 2, 5 and 10 cm again a significantly lower proportion of larvae was recovered in the site, but no differences in proportions were observed between these three distances (Tukey HSD, P > 0.05).

Bottom Line: However, proportions of larvae reaching the site decreased rapidly with increasing distance.Fourth-instar larvae survived significantly longer and we estimated that the maximum survival time was 113 hrs.In addition, the results suggest that, for larval vector control methods to be effective, habitats should remain drained for at least 5 days to kill all larvae (e.g. in rice fields) and habitats that recently dried up should be treated as well, if larvicidal agents are applied.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory of Entomology, Department of Plant Sciences, Wageningen University, The Netherlands. sander.koenraadt@wur.nl

ABSTRACT

Background: Although the effects of rainfall on the population dynamics of the malaria vector Anopheles gambiae have been studied in great detail, the effects of dry periods on its survival remain less clear.

Methods: The effects of drying conditions were simulated by creating desiccated habitats, which consisted of trays filled with damp soil. Experiments were performed in these trays to (i) test the ability of An. gambiae sensu stricto eggs to hatch on damp soil and for larvae to reach an artificial breeding site at different distances of the site of hatching and (ii) to record survival of the four larval stages of An. gambiae s.s. when placed on damp soil.

Results: Eggs of An. gambiae s.s. hatched on damp soil and emerging larvae were capable of covering a distance of up to 10 cm to reach surface water enabling further development. However, proportions of larvae reaching the site decreased rapidly with increasing distance. First, second and third-instar larvae survived on damp soil for an estimated period of 64, 65 and 69 hrs, respectively. Fourth-instar larvae survived significantly longer and we estimated that the maximum survival time was 113 hrs.

Conclusion: Short-term survival of aquatic stages of An. gambiae on wet soil may be important and adaptive when considering the transient nature of breeding sites of this species in sub-Saharan Africa. In addition, the results suggest that, for larval vector control methods to be effective, habitats should remain drained for at least 5 days to kill all larvae (e.g. in rice fields) and habitats that recently dried up should be treated as well, if larvicidal agents are applied.

Show MeSH
Related in: MedlinePlus