Odour detection Flashcards
semiochemicals
behaviour modifying chemicals
pheromones
Releaser - chemicals that induce immediate behaviour change
Primer- initiate developmental change but not behaviour change
Allelochemicals
Kairomones - favourable to receiver not emitter - co2
Allomones - favourable to emitter niot receiver - natural repellant
synomones - favourable to both emitter and receiver
Maxillary palp
comprised of 5 segments
primary Co2 sensing organ
also detect 1-octen-3-ol produced by humans and cattle
proboscis
tip of proboscis - labellum- detects odour
low volatile compounds for short range detection
Antenna
flagellum divided into 13 distinct flagellomeres (segments)
female antenna have chemosensilla on all flagellomeres
long range detection of volatile chemicals
Olfactory sensilla
all three appendages have porous olfactory sensilla
hair like projections
Odourant binding proteins (OBP)
binds to odour molecule and carries it across lymph to olfactory receptor neurone
Olfactory receptors
when odour molecule reaches dendrite it binds to an olfactory receptor
ORs activate signal transduction inside cell - leads to depolarisation of Olfactory receptor neurone which generates action potential
3 classes of chemosensory receptors in An. gambiae
Olfactory - odours from humans
ionotrophic - odours from humans
gustatory - phermones and Co2
Orco - co receptor
ORs need OR co -receptor for correct signalling to take place
found in antenna and mouthparts
candidate for genetic targeting in mosqs
mutants with no Orco don’t respond to human odour
Olfactory receptor neurones
sensitive to concentration
detect specific ratios of chemical within a mixture
facilitated by co-location of two ORNs in one sensillum- coincidence detection
Coincidence detection
2 chemicals produced by humans and one chemical produced by cows and plants
if two odours come in at same time know that it is human
Odour degrading enzymes
once the odour molecule and the OBP has bound to the OR, ODEs break down the odour molecule to halt stimulation of the receptor
if stop ODEs mosq. becomes confused
