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11/17/2015
1
Major categories of Sense Organs
1. Mechanoreceptors (movement: tactation, proprioception, and hearing)• Trichoid sensilla
• Placoid sensilla
• Campaniform sensilla
• Chordotonal sensilla
2. Chemoreceptors (chemicals: substrate & airborne)• Trichoid sensilla
• Cone or Basicone (basiconic) peg sensilla
• Coeloconic peg sensilla
• Sensory pits
3. Photoreceptors (photons: light and heat)
4. Less common types:• Thermoreceptors (temperature: e.g., mammalian parasites)
• Hygroreceptors (humidity: e.g., some beetles, lice)
• Magnetoreceptors (magnetic fields: e.g., bees)
cuticleepidermis
scolopale
base of seta
vacuole
tormogencell
trichogen cellsense cellaxon
axon bundle
sense cells
tormogen cell
scolopalemembrane
scolopaledendrite
tormogen cell
sensecell
cuticle
thickened barouter lamella
inner lamella
epid.
attachmentor cap cell
scolopale rod
scolopale orenvelope cell
fibrous sheath cell(not always present)
neuron
glial cell
scolopale cap
CHORDOTONAL SENSILLUM
CAMPANIFORM SENSILLUM
PLACOID SENSILLUM
TRICHOID SENSILLUM Mechanoreceptors
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Trichoid sensilla from Anopheles mosquito antenna(tactation)
Placoid sensillaon honey beeflagellomeres
(tactation)
flagellum
scape
pedicel
1 mm
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Campaniform sensilla(cockroach leg: proprioception)
HAIR PLATES or HAIR BEDS
mat of trichoid sensilla
hardened cuticlemembrane
axons
sense cells(neurons)
scolopale(envelope)
cellcap cell
accessorycell
cuticleepidermis
scolopale
tympanal membrane
cap cell
fibrous sheath cell
axon bundle
neuron(sense
cell)
SUBGENUAL ORGAN
TYMPANAL ORGAN
JOHNSTON’S ORGAN
flagellum STRETCH RECEPTOR
axonnerve axons
pedicelouter ring ofscolopidia
inner ring ofscolopidia
scapeaxon bundles
nerve cell body multi-polar
neuron muscle
Chordotonalsensilla
(mostly, hearing)
(proprioception)
(proprioception)
scolopale cells
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Hair plates: left prosternal organ in a mantis(Dictyoptera: Mantodea -- proprioception)
base of head
prosternal organ
neck sclerites
Joe Singleton 2001
Johnston’s organ – whirligig beetles(Coleoptera: Gyrinidae -- tactation)
water surface
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Johnston’s organ – mosquitoes(Diptera: Culicidae -- hearing)
Male starts, then matches female frequency (Gibson & Russell 2006)
Tympanal organs (Orthopteroid insects – hearing)
cap cells
sensoryneurons
katydid ear(Tettigoniidae)
mantis ear(ultrasound)(Mantidae)
grasshopper ear(Acrididae)
scolopale cells
tympanum
tympanal membrane
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More tympanal organs (Cicadidae)
(approx. 1500 chordotonal sensilla per tympanum)
male
X
Y
More tympanal organs (Lepidoptera: bat detection )
Night-flying butterfly,Hedylidae: at base of
wing (ultrasound)
Night-flying moth, Noctuidae:rear of thorax (ultrasound)
right ear
TWOchordotonal
sensilla
tympanalmembrane
B cell
A1 & A2
tracheal sac tracheal sac
tracheal sac
trachealsac
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More tympanal organs(Chrysopidae: bat detection )
scolopidia(≈ 25)
tympanalmembrane
swelling
Lee Miller, 1970, ‘71, ‘75
Tympanal organ
accessory & cap cells
(to wing tip)
C
(to wing tip)
pegopenings in cuticle
cuticle
scolopale
vacuoletormogen cell
epidermis
trichogen cell
axon bundlesensory neurons
branching dendrites
opening in cuticle opening (peg)
peg
vacuole
sensory neurons
epidermis
tormogencell
scolopale
axon bundlescolopale
neurons &supporting cells
opening
sensorypeg
trichogen cell
Chemoreceptors
COELOCONIC PEG
TRICHOIDSENSILLUM(hole in tip)
BASICONIC PEG(thin-walled)
SENSORY PIT(found in all insects)
>30,000 in Apidae!
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Basiconic peg sensilla
Anopheles mosquito antenna
Heliothismoth
haustellum
Coeloconic peg from Anopheles mosquito antenna
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Male moth antennae: the gold standard for olfaction
> 70,000 olfactory sensors
Trail-followingin ants:
another olfactorytour de force
An Old World army ant, Aenictus sp.
More than 40 glands secrete complexes of
chemicals in ants.
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The insect visual sense: PhotoreceptionLight: Visible, IR, UV (different λ’s)
Major categories ofvisual sense organs
1. Dermal receptors (simple epidermal cells)• many larval insects
• all stages of cockroaches
• in cephalopharyngeal skeleton of muscoid maggots
2. Dorsal ocelli (“true ocelli”)• 4 (ancestor) 3 (middle one can be “bilobed”) 2 0
• …or 2 (ancestor) 3 (Crustacea + Insecta) 2 0
• can’t form an image
• fast response time; responds to very low levels of light
3. Stemmata (“lateral ocelli”)• larvae of just about all Hemimetabola (Endopterygota)
• capable of forming an image (but may not use it)
4. Compound eyes (multi-faceted)• Not in larval Hemimetabola
• primary visual sense organs of insects
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Dorsal Ocellus
Dorsal (true) ocelli – damselfly (Odonata: Zygoptera)
lens
retinal apparatus
Simple eyes: stemmata (“lateral ocelli”) – larvae of Lepidoptera
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epidermis
DORSAL OCELLUS
corneal lenscorneagen cells
cuticle
pigment cells
pigment cell
rhabdomretinula cell
ocellar nerveto protocerebrum
retinula (sense) cell
corneal lens
cuticle
epidermis
retinula cells
rhabdompigment
corneagen cellscrystalline cone (lens)
ocellar nerveto protocerebrum
ocellar nerve (optic nerve)
STEMMA(“lateral ocellus”)
cross-section of retinal apparatus
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