Fluctuating asymmetry in larvae of Brachythemis sp. (Odonate: Libellulidae)

Random and subtle deviations from bilateral symmetry (fluctuating asymmetry) have long been of interest to biologists who wish to study the susceptibility of organisms to changes in environmental quality. We examined fluctuating asymmetry (FA) in larvae of the genus Brachythemis sp. (Odonata: Libellulidae) from four small, relatively disturbed rivers (Banco, Anguédédou, Dougodou and Bou) in Côte d'Ivoire as a water quality assessment tool. In situ measurements of water pH, temperature, conductivity and dissolved oxygen were made at two sampling points along each river. Water was sampled and analyzed in the laboratory for nitrate, nitrite, phosphate, manganese, and ammonium concentrations. The left and right sides of 11 segments were photographed separately using a portable digital microscope (Celestron 2.0). Thus, the perimeter, the surface area of both sides of the labial palp, the ocular diameter, and the length of the different appendages (femur, tibia, and tarsus) of the 3 legs were measured using the imageJ measurement software. This study revealed that the water quality of each river affects the developmental stability of Brachythemis sp. We concluded that the length of the first femur (LF1) and the length of the third tibia (LT3) are useful bioindicators for this taxon because the impact of fluctuating asymmetry on these traits was strongly associated with five physicochemical parameters of each River.