The role of 2,6-dichlorophenol as sex pheromone of the tropical horse tick Anocentor nitens (Acari: Ixodidae).

The objective of this study was to evaluate the role of 2,6-dichlorophenol (2,6-DCP) as sex pheromone of Anocentor nitens. Sex pheromones were extracted by submerging 150 female fed for 6 days in hexane (3 ml) for two hours and sonicating them for 15 min. The extract was analyzed by GC-MS employing the Single Ion Monitoring (SIM) method. Identification of 2,6-DCP was based on the comparison of mass spectra with a computer search using the NIST library and by matching the mass spectrum of the peak at the retention time of 2,6-DCP from extracts and the synthetic product. In an olfactometer, males were released at 2.5 cm from females, control rubber septa and impregnated rubber septa with increasing concentrations of 2,6-DCP (50, 500 and 5000 ng). A higher percentage of orientation and higher frequencies of angles between 0 degrees and 10 degrees were observed for males tested with females than with controls. Attraction of males to dummies impregnated with 2,6-DCP was observed with highest response (100%) at 50 ng. There was a gradual decrease of responsiveness of males with increasing concentration of 2,6-DCP (70 to 75%). This compound stimulated a behavior of mounting and ventral positioning of A. nitens males at the lowest 2,6-DCP concentration whereas dummies impregnated with 2.6-DCP higher than 50 ng concentration inhibited these behaviors. Therefore, we can conclude that 2.6-DCP can elicit the complete behavior sequence of orientation, location, mounting and ventral positioning behaviors and plays a role as an attractant and, as a mounting sex pheromone in A. nitens.