title: Water vapour and heat combine to elicit biting and biting persistence in tsetse.
abstract: BACKGROUND
  Tsetse flies are obligatory blood feeders, accessing capillaries by piercing the skin of their hosts with the haustellum to suck blood. However, this behaviour presents a considerable risk as landing flies are exposed to predators as well as the host's own defense reactions such as tail flicking. Achieving a successful blood meal within the shortest time span is therefore at a premium in tsetse, so feeding until replete normally lasts less than a minute. Biting in blood sucking insects is a multi-sensory response involving a range of physical and chemical stimuli. Here we investigated the role of heat and humidity emitted from host skin on the biting responses of Glossina pallidipes, which to our knowledge has not been fully studied in tsetse before.
  
  
  METHODS
  The onset and duration of the biting response of G. pallidipes was recorded by filming movements of its haustellum in response to rapid increases in temperature and/or relative humidity (RH) following exposure of the fly to two airflows. The electrophysiological responses of hygroreceptor cells in wall-pore sensilla on the palps of G. pallidipes to drops in RH were recorded using tungsten electrodes and the ultra-structure of these sensory cells was studied by scanning and transmission electron microscopy.
  
  
  RESULTS
  Both latency and proportion of tsetse biting are closely correlated to RH when accompanied by an increase of 13.1°C above ambient temperature but not for an increase of just 0.2°C. Biting persistence, as measured by the number of bites and the time spent biting, also increases with increasing RH accompanied by a 13.1°C increase in air temperature. Neurones in wall-pore sensilla on the palps respond to shifts in RH.
  
  
  CONCLUSIONS
  Our results show that temperature acts synergistically with humidity to increase the rapidity and frequency of the biting response in tsetse above the levels induced by increasing temperature or humidity separately. Palp sensilla housing hygroreceptor cells, described here for the first time in tsetse, are involved in the perception of differences in RH.
authors: Institute of Biology, Laboratory of Animal Physiology, University of Neuchâtel, Rue Emile-Argand 11, Neuchâtel, Switzerland. charles.chappuis@unine.ch
authors: Charles J F
authors: CJ
authors: Chappuis
authors: Steve
authors: S
authors: Béguin
authors: Michèle
authors: M
authors: Vlimant
authors: Patrick M
authors: PM
authors: Guerin
mesh_terms: D000818:Animals; D001831:Body Temperature; D005247:Feeding Behavior; D006790:Host-Parasite Interactions; D006358:Hot Temperature; D006813:Humidity; D007299:Insect Bites and Stings / Q000469:parasitology* / Q000503:physiopathology; D014370:Tsetse Flies / Q000502:physiology*
references: Ann Trop Med Parasitol. 1985 Aug;79(4):457-61
references: 4073997
references: Annu Rev Entomol. 2001;46:79-110
references: 11112164
references: Parasitology. 1993 Apr;106 ( Pt 3):277-82
references: 8098147
references: Trans R Soc Trop Med Hyg. 1972;66(2):318-9
references: 5048819
references: Nature. 1967 Nov 25;216(5117):794-5
references: 6074947
references: Experientia. 1975 Jun 15;31(6):694-5
references: 1140299
references: Pest Manag Sci. 2007 Jan;63(1):17-22
references: 17089333
references: Med Vet Entomol. 1992 Jul;6(3):231-40
references: 1421503
references: Nature. 1969 Mar 1;221(5183):855-6
references: 5774156
references: J Exp Biol. 2013 Apr 1;216(Pt 7):1292-306
references: 23264482
references: Am J Trop Med Hyg. 1954 Jan;3(1):160-71
references: 13114601
references: Front Physiol. 2011 Oct 25;2:74
references: 22046163
references: J Physiol. 1963 Nov;169:394-403
references: 14079675
references: J Vector Ecol. 2008 Jun;33(1):145-9
references: 18697317
references: Med Vet Entomol. 1991 Jul;5(3):335-50
references: 1768925
references: J Insect Physiol. 2011 Oct;57(10):1446-9
references: 21806990
references: J Insect Physiol. 2011 Aug;57(8):1070-84
references: 21640726
references: Med Vet Entomol. 1999 Feb;13(1):2-23
references: 10194745
references: J Physiol. 1963 Jul;167:427-47
references: 13932165
references: J Insect Physiol. 1970 Jan;16(1):61-74
references: 5417708
references: J Econ Entomol. 1971 Apr;64(2):442-3
references: 5551925
references: Proc Natl Acad Sci U S A. 2012 Jun 12;109(24):9471-6
references: 22645365
references: J Insect Physiol. 1970 May;16(5):991-1000
references: 5449734
references: J Neurophysiol. 2010 Jun;103(6):3274-86
references: 20375249
references: Ann Trop Med Parasitol. 1980 Apr;74(2):219-37
references: 7436606