| dc.description.abstract | Anopheles gambiae larvae and pupae inhabit mainly small, transient, sunlit and turbid pools. These habitats exhibit different productivity levels. The factors responsible for this differential productivity are important in developing and assessing the feasibility of larval control strategies. The main aim of this study was to identify and assess the factors responsible for differences in mosquito productivity among habitats. Possible factors include nutrients, bacteria and algae, as well as predators and parasites. 183 larval habitats were sampled cross-sectionally for four weeks. Productivity in each habitat was measured by larval density estimation. Algal abundance was quantified by direct counting methods. The importance of nitrogen was assessed by use of artificial habitat arrays. Poisson regression analyses using the GENMOD procedures in SAS version 8.0 (SAS Institute) showed that drainage channels and rain pools were significantly more productive compared to swamps. Tyre tracts were significantly the least productive habitat type relative to swamps. Overall, habitat type was significantly associated with larval productivity (Wald X2 =203.36, df=6,p<0.000l). Ponds and tyre tracts were significantly more turbid compared to swamps. Overall, turbidity was significantly associated with habitat types (Wald X2 =148l.56, df=6, p<. 0001). Drainage channels had the highest phosphorus concentrations compared to swamps even though the differences were not significant. Streambeds had the lowest concentrations of phosphorus compared to swamps but the difference was not significant. Overall, phosphorus concentration was significantly associated with habitat types (Wald X2 = 11178.6, d.f=6,p<.000 l). Ponds had the largest significant area compared to swamps while drainage channels had the least area compared to swamps but the difference was not significant. Overall, habitat area was not significantly associated with habitat types (Wald X2 =7.22, df=6,p<. 0.3012). Streambeds had the highest pH values compared to swamps while burrow pits had the least pH compared to swamps but neither of the differences was significant. Overall, water pH was not significantly associated with habitat type (Wald X2 =0.37.8, df=6, p< 0.9990). Drainage channels had the highest and significant water nitrogen concentration compared to swamps while tyre tracts had the lowest nitrogen concentration compared to swamps but the difference was not significant. Overall, water nitrogen concentration was significantly associated with habitat type (Wald X2 =203.36, df=6, p< <0.0001). Streambeds had the highest algal densities followed by drainage channels while ponds had the lowest densities (p<O.OOl). Overall, algal densities were significantly different among the seven habitat types (Wald X2 =4531.60, df=6, p< <0.0001) pH had a significant effect on larval productivity and was negatively associated with larval density (p<O.Ol). Turbidity had a significant effect on larval productivity and was positively associated with larval density (p<O.Ol). There was positive but not significant association between algal density and larval densities (p<O.Ol).
The mean adult dry weight, percentage emergence, and mean development time of An. gambiae - Kisumu strain in artificial habitats of (p<0.05) were not significantly affected by nitrogen supplementation. However larval density had a significant effect on the same. There was no interaction effect of nitrogen supplementation and larval density on mean adult dry weight | |
