Universidad de El Salvador, El Salvador
Title: Exploration of Morphological Patterns inTriatoma dimidiata (HemÃptera: Reduviidae) through Ecological Variables in El Salvador
Introduction: Chagas disease is a parasitic infection caused by the protozoan Trypanosoma cruzi, whose symptoms often reduce patient’s quality of life and causes economic losses in developing countries. This parasite infects humans when the insects (vectors of the Triatominae subfamily) that carry the parasite, move from their natural habitat to homes in search of food. In El Salvador by 2005, forest cover was 5.8%, while by 2012, most of the territory was used in agricultural activities, leaving patches of natural ecosystems, causing humans and the vectors of the disease to occupy the same habitat. Since Triatoma dimidiata is considered the main vector of the country and it presents morphological and genetic variation throughout its range of distribution, resulting in different behaviors that influence the epidemiology of the disease, it is important to evaluate ecological variables such as, use and type of soil, life zones and elevation, as possible factors responsible for the morphological variability of the triatomine bug populations in El Salvador. Materials and methods: The Health’s Ministry Vector Units of five regions donated 51 triatomines, bugs were analyzed in the Laboratory for Medical Entomology LEV (by its acronym in Spanish). The photographs used for the analysis were taken with a CANON PowerShot-A2200 camera. Individuals were georeferenced in QGis Version 2.16.2, using the tool intersection: the geographical position of the individuals, their photometry data and shapefiles like Soil-Use, Pedological-Map, Life-Zone and Elevation datasets were grouped into an Excel-2016 sheet and exported to the STATISTICA 6 software for following Shapiro-Wilks tests. The data from a normal distribution were treated with ANOVA or T test to determine if there was any significant difference, and for those with non-normal distribution we applied the Kruskal-Wallis, Mann-Whitney U or Spearman correlation test to identify if there was some significant difference between the variables. Results: These are the variables with significant difference in Soil Type: Entire Body Area (p = 0.00855), Body Total Color Intensity (p = 0.00013), Entire Body Total Color Intensity (0.0001), Body Area (p = 0.0011), Light Ventral Side Total Color Intensity (p = 0.0001), Light Body Area (p = 0.0046), Dark Ventral Side Total Color Intensity (p = 0.0019). The following variables show a low correlation with Elevation: Wing Proportion (R = 0.31, P = 0.03), Body Total Color Intensity (R = -0.37, P = 0.006), Body Area (R = -0.28, P = 0.04), Body Shape (R = -0.29, P = 0.03). The following variables present a significant difference in Land-Use: Entire Body Color Intensity (p = 0.03113), Wing Area (p = 0.04962), Entire Body Area (p = 0.00086), Body Total Color Intensity (p = 0.00000), Wing Total Color Intensity (p = 0.0033), Entire Body Total Color Intensity (p = 0.0007), Body Area (p = 0.0008), Body Shape (p = 0.0019), Light Ventral Side Total Color Intensity (p = 0.0033), Dark Ventral Side Total Color Intensity (p = 0.0061). The following variables present a significant difference in relation to Life-Zone: Body Total Color Intensity (U = 179.0000), Spots Shape (U = 180.0000), Body Shape (U = 161.0000). Conclusion: T. dimidiata presents plasticity in its Body Shape and Color Intensity in relation with land use, life zone and type of soil, this could be due to changes that occur in natural ecosystems i.e. anthropogenic activity, causing a morphological variation of T. dimidiata in the Tropical and Sub-Tropical Humid Forests.