Date of Award

Fall 1992

Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences


Ecological Sciences

Committee Director

Daniel E. Sonenshine

Committee Member

Keith A. Carson

Committee Member

Norman J. Fashing


The foreleg claw sensilla were determined to be the receptors of the female contact sex pheromone, MSP (mounting sex pheromone), in D. variabilis, D. andersoni and A. americanum male ticks. In all three tick species, the claw sensilla consists of six anteriorly-directed setae arranged in three symmetrical pairs, two each on the opposite sides of the apotele of the claw and one on the ventral side. Behavioral bioassays and morphological study of these setae revealed that only the dorsal and middle (= lateral) pairs of claw sensilla are mechanogustatory, while the ventral pair are strictly mechanoreceptors. The dorsal and middle sensory setae exhibit a single pore-like structure located at their tip, a feature characteristic of gustatory or mechanogustatory sensilla similar to those found on the palps that are believed to function as pheromone receptors. Similarities in structure and function with contact chemosensilla of insects also are discussed.

In all three tick species, male mounting and post-mounting behaviors were suppressed only when the dorsal and middle pairs of claw sensilla were ablated or covered with gelatin; normal behavior was restored when the gelatin was removed. Dose-response bioassays were conducted with D. variabilis males to authenticate the results of the gelatin tests. The results of these bioassays demonstrated that the gelatin did not permit molecular penetration of the pheromone. Results of transfer of stimulus bioassays, in which only the MSP, cholesteryl oleate, was applied to inanimate objects (beads), demonstrated that male ticks responded only to the pheromone and mating behavior could be regulated by covering or uncovering the foreleg claw sensilla with gelatin. The significance of these findings for an understanding of mating behavior in ixodid ticks is discussed.


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