Variation over time in wing size and shape of the coastal malaria vector Anopheles (Cellia) epiroticus Linton and Harbach (Diptera: Culicidae) in Samut Songkhram, Thailand

OBJECTIVE: Anopheles (Cellia) epiroticus Linton & Harbach, a coastal mosquito (also called a brackish mosquito), is a secondary vector species of malaria distributed throughout eastern and southern regions of Thailand. This research aimed to investigate the differences of wing size and shape of this female Aonpheles species in Samut Songkhram Province, Thailand occurring over time between 2015 and 2017. MATERIALS AND METHODS: Coordinates of 13 landmarks were selected and digitized. Centroid size (CS) was used to estimate wing size. Shape variables were used to estimate wing shape and were calculated from the Generalized Procrustes Analysis following principal components of the partial warp. The statistically significant differences of the average wing size based on CS and wing shape based on Mahalanobis distances in each year were estimated using the non-parametric permutation testing with 1,000 cycles after Bonferroni correction with a significance level of 0.05 (p < 0.05). RESULTS: The A. epiroticus population in year 2016 had the highest average (3.61 mm), and the population in year 2017 had the lowest (3.47 mm). In this study, there was no difference in the size of wing between A. epiroticus population in the years 2015 and 2016 (p > 0.05). The A. epiroticus population in year 2017 was significantly smaller than the population in the years 2015 and 2016 (p < 0.05). All pairwise comparisons of wing shape Mahalanobis distances were significantly different in year 2017 compared with 2015 and 2016 (p < 0.01). CONCLUSION: These results indicate differences of wings occur over time that affect the morphological variability of A. epiroticus. The differences in weather conditions in each year affect the adaptive and morphological changes of mosquitoes in coastal areas.