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Ammonia-sensitive neurones on the first tarsi of the tick, Rhipicephalus sanguineus

1980; Elsevier BV; Volume: 26; Issue: 8 Linguagem: Inglês

10.1016/0022-1910(80)90126-2

1879-1611

Deborah Haggart, Edward E. Davis,

Insect-Plant Interactions and Control

Two types of ammonia-sensitive neurones were found on the first tarsi of the tick, Rhipicephalus sanguineus. These cells were located in the anterior pit and medial groups of sensilla on the dorsal surface of the tarsus. Ammonia-sensitive neurons showed phasic and/or tonic response patterns that were proportional to the ammonia intensity over the range of 0.2 to 100 × 10−9 moles/sec. Both types of ammonia-sensitive neurones were ‘slow-adapting’ in that they maintained their tonic responses to ammonia during periods of prolonged stimulation. Individual ammonia-sensitive cells varied in sensitivity to ammonia. As a group, the anterior pit neurones were more sensitive than the medial group neurones throughout the concentration range examined. The high degree of specificity for ammonia of ammonia-sensitive neurones was shown by their lack of responsiveness to most other stimuli presented at physiological intensities. Preliminary behavioural studies reveal that low levels of ammonia elicit questing responses from R. sanguineus. This finding, coupled with the electrophysiological evidence for primary afferent neurones sensitive to low levels of ammonia, supports the concept that ammonia plays a role in directing host-seeking or other behaviours of R. sanguineus.