Study of foveae dorsales of nymphs and adults of four species of ticks (Acari: Ixodidae) by scanning electron microscopy

The foveae dorsalis, the external opening of the sex pheromone 2,6-dichlorophenol producer gland, of Amblyomma cajennense, Dermacentor nitens, Rhipicephalus (Boophilus) microplus and Rhipicephalus sanguineus was studied with scanning electron microscopy. At least three specimens from each stage: unfed larvae, nymphs, females and males, and females fed for 4 to 6 days were examined. The foveae dorsales were not observed in larvae and R. (B.) microplus males. The foveae dorsales were observed as paired depressions, below the scutum in nymphs and females. In males they appeared as paired subtle elevations, located (2/3) of the way along the idiosoma. Generally the larger structures with a higher number of pores were observed in A. cajennense. Males and nymphs showed foveae dorsales of similar sizes but smaller than those of females. After feeding, secretions were observed in D. nitens and A. cajennense foveae dorsalis. In R. sanguineus and R. (B.) microplus this kind of secretion was not observed. An attempt to connect the appearance of foveae dorsalis with the role of 2,6-dichlorophenol in tick copula has been made. The occurrence of D. nitens females with three foveae dorsales was described.