Responses of the tropical bont tick Amblyomma variegatum to
its aggregation-attachment-pheromone and to host odour on a
C. McMahon &
Zoology, University of Neuchâtel, Rue Emile-Argand 11, 2007
variegatum ticks release a mixture of o-nitrophenol (ONP) and
methyl salicylate (MS) from dermal glands that develop soon after
infesting a host. These products serve to attract conspecifics to
the attachment site. The behavioural responses of A. variegatum
adult males and females were recorded on a servosphere to vapours
of both these compounds presented in an air stream. In the absence
of the air stream A. variegatum adults walk on all eight
legs but with long halts. An air stream causes continuous walking
and induces a reaching response where the first leg pair is used
to actively sample the air. This increases the angular velocity of
the displacement and reduces walking speed. Air-current effects on
behaviour are amplified in the presence of vapours of ONP and MS
in the air flowing over the ticks. Males and females are equally
attracted to low source doses of ONP and MS presented alone.
Vapours from a 1:1 binary mixture of ONP and MS attract over the
10 4 -fold source dose range of 10ng to 100µg (10 9 -10 14
molecules/ml of air), but attraction to vapours from the binary
mix is significantly reduced at source doses over 100µg.
Attraction was higher to this 1:1 mixture than to the natural
ratio released from the dermal glands of males, where ONP vapour
predominates. This indicates that A. variegatum adults are
sensitive both to the quality and quantity of the odour presented.
Although the response to ONP vapour is variable on its own, it is
consistently attractive when delivered with steer hair odour -
unattractive on its own. Moreover, no change in angular velocity
or speed was observed in the the upwind walk to this combination.
This supports the hypothesis that the response to the pheromone is
enhanced by host odour.
Amblyomma, pheromone, host relations, behaviour
Copyright: The copyrights of
this abstract belong to the author (see right-most box of title
table). This document also appears in Session 13 – INSECT
PHISIOLOGY, NEUROSCIENCES, IMMUNITY AND CELL BIOLOGY Symposium
and Poster Session, ABSTRACT BOOK II – XXI-International
Congress of Entomology, Brazil, August 20-26, 2000.