Lecture 21

11/12/2015
ocelli
frontal nerve (to cibarium)
compound eye
PROTOCEREBRUM
red & black = CNS
blue = VNS
lateral connectives
neurosecretory cells
DEUTOCEREBRUM
FRONTAL GANGLION
to antenna
BRAIN
TRITOCEREBRUM
frontal connective with tritocerebrum
MOUTHPARTS:
to labrum
SUBESOPHAGEAL
GANGLION
recurrent nerve
postesophageal (paraesophageal) connectives
1 2
3
4
2 3 4
5
6
CORPUS CARDIACUM
circumesophageal connective
to mandible
to maxilla
to labium & hypopharynx
HYPOCEREBRAL GANGLION
1
CORPUS ALLATUM
SUBESOPHAGEAL GANGLION
VENTRICULAR (INGLUVIAL) GANGLION
ventral nerve cord
TRITOCEREBRUM
DEUTOCEREBRUM
BRAIN:
PROTHORACIC
GANGLION
PROTOCEREBRUM
to anterior body wall
to leg
to posterior body wall
to spiracle & alary muscles
to anterior body wall
to wing
to leg
to posterior body wall
MESOTHORACIC
GANGLION
to spiracle & alary muscles
CAUDAL GANGLION
(METATHORACIC & ABDOMINAL
ganglia not shown)
caudal nerve
Centralization of CNS
(1)
(2)
(0)
Apterygota
(unspecialized)
e.g. 8 abdominal
ganglia
(7 in Odonata)
(5/6 in Orthoptera)
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Types of neurons
dendrites
UNIPOLAR (motor & associative)
axon
cell body
BIPOLAR (sensory)
axon
dendrites
MULTIPOLAR (sensory)
neurofibrillae
axon
dendrites
Nerve connections
axons of unipolar
motor neurons
muscle
GANGLION
multipolar stretch
receptor (sensory)
associative neuron
(unipolar)
seta
epidermis
cuticle
axons of bipolar
sensory neurons
INTEGUMENT
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Brain or ganglion, cross-section
neural lamella
Typical nerve
perineurium (secretes
the neural lamella)
giant fibers
nerve cell bodies
fiber tracts
Glial cells:
1. Protection (cushioning)
2. Nutrition (passing nutrients &
salts to neurons)
3. Food storage (glycogen)
4. Insulation (for delicate, leaky
neurons/axons)
neuropile (principal
site of synapses)
The insect brain
ocellar nerve
optic lobe
antennal
nerve
(frontal
ganglion)
Protocerebrum
Deutocerebrum
Tritocerebrum (2nd ant.)
circumesophageal
connective
postesophageal
connective(s)
Subesophageal
ganglion
Grasshopper brain
(Orthoptera)
Same as 520my-old 3-part brain of
earliest arthropods, e.g. Fuxianhuia.
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The CNS: anterior components
corpus cardiacum
ocellar nerve
PROTOCEREBRUM
hypocerebral ganglion
antennal nerve
AORTA
ocellar nerve
corpus allatum
DEUTOCEREBRUM
inner esophageal nerve
position of molt gland
TRITOCEREBRUM
frontal ganglion
lateral connective
ventricular (ingluvial)
ganglion`
recurrent nerve
circumesophageal connective
labral nerve
mandibular nerve
SUBESOPHAGEAL
GANGLION
PROTHORACIC GANGLION
hypopharyngeal nerve
nerve to neck
maxillary nerve
labial nerve
ocelli
frontal nerve (to cibarium)
compound eye
PROTOCEREBRUM
Ganglia posterior
to the brain
lateral connectives
neurosecretory cells
DEUTOCEREBRUM
FRONTAL GANGLION
TRITOCEREBRUM
frontal connective with tritocerebrum
labral nerve
recurrent nerve
postesophageal (paraesophageal) connectives
CORPUS CARDIACUM
circumesophageal connective
to mandible
(to hypopharynx)
to maxilla
to labium (& hypopharynx?)
HYPOCEREBRAL GANGLION
CORPUS ALLATUM
SUBESOPHAGEAL GANGLION
VENTRICULAR (INGLUVIAL) GANGLION
ventral nerve cord
PROTHORACIC
GANGLION
to anterior body wall
to leg
to posterior body wall
to spiracle & alary muscles
MESOTHORACIC
GANGLION
to anterior body wall
to wing
to leg
to posterior body wall
to spiracle & alary muscles
CAUDAL GANGLION
(METATHORACIC & ABDOMINAL
ganglia not shown)
caudal nerve
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Brain sizes (as fraction of body weight)
Dytiscidae (Coleoptera): 1/4000
Termitinae (Isoptera): 1/280
Pompilidae (Hymenoptera): 1/400
Apidae (Hymenoptera): 1/75
Mushroom bodies or corpora pedunculata
(Ex. = worker ant brain)
…and in Drosophila
yellow = visual data
red = olfactory data
blue = higher associative centers
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Giant fibers (axons):
No synapses, large diameter
ventral nerve cord of
Syrphidae (Diptera)
20-60 µ
?
Deuterostomia
Lophotrochozoa
<5µ
Insecta
Nematodes
Ecdysozoa
Myelinated (red) (100x faster)
Non-myelinated (blue)
Evolution of myelinated axons (red)
The VNS: Stomatogastric components
corpus cardiacum
ocellar nerve
protocerebrum
hypocerebral ganglion
antennal nerve
AORTA
ocellar nerve
corpus allatum
deutocerebrum
inner esophageal nerve
position of molt gland
tritocerebrum
frontal ganglion
lateral connective
ventricular (ingluvial)
ganglion
recurrent nerve
circumesophageal connective
labral nerve
subesophageal
ganglion
prothoracic ganglion
mandibular nerve
hypopharyngeal nerve
nerve to neck
maxillary nerve
labial nerve
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ocelli
frontal nerve (to cibarium)
compound eye
PROTOCEREBRUM
Visceral
Nervous System
(in blue)
lateral connectives
neurosecretory cells
DEUTOCEREBRUM
FRONTAL GANGLION
TRITOCEREBRUM
frontal connective with tritocerebrum
labral nerve
recurrent nerve
postesophageal (paraesophageal) connectives
CORPUS CARDIACUM
circumesophageal connective
to mandible
to maxilla
HYPOCEREBRAL GANGLION
CORPUS ALLATUM
to labium & hypopharynx
SUBESOPHAGEAL GANGLION
VENTRICULAR (INGLUVIAL) GANGLION
ventral nerve cord
PROTHORACIC
GANGLION
to anterior body wall
to leg
to posterior body wall
to spiracle & alary muscles
MESOTHORACIC
GANGLION
to anterior body wall
to wing
to leg
to posterior body wall
to spiracle & alary muscles
CAUDAL GANGLION
caudal nerve
Stomatogastric
VNS Function
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CNS function: Reflex behavior
1. Reflex excitability – e.g. light, through dorsal ocelli
2. Reflex immobilization – total inhibition of CNS
•
•
•
Thanatosis
Warning attitudes (e.g. caterpillars)
Camouflage (e.g. stick insects)
3. General immobilization (insect “sleeps”)
•
•
•
Remove antennae
Remove halteres in Diptera
Block off all ocelli
4. Note: Brain is the inhibitory center
•
Example: mantis male with head eaten
Nymphalis antiopa – the mourning cloak butterfly
(experiments on neural integration)
(also: brain ruling ganglia)
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Reflex immobilization (Thanatosis)
Thanatosis in a gryllid
“Death-feigning beetle,”
Crytoglossa variolosa (Tenebrionidae)
Learning
1. Habituation (learning not to respond)
•
•
cedarwood oil or some other challenge
constant prodding of a cockroach
2. Conditioning (responding to something
previously ineffectual)
•
floral odors; stimulus assoc. w/ feeding
3. Imprinting (special type of conditioning)
•
•
critical developmental stage (plasticity)
host shifts, host fidelity, and speciation
4. Trial and Error
• beetle courtship – “long axis”
5. Latent Learning (recognition of
landmarks)
•
antlion
Note: Percent of brain
made up of corpora
pedunculata:
workers = 13.5%
queen = 9.2%
drones = 5.6%
Pompilidae (Hymenoptera)
solitary wasps, bee foraging, ant mazelearning
6. Time sense (cuing to 24 hour cycle)
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“Sophisticated” Learning
Latent learning (landmark orientation)
(Digger wasp – Hymenoptera: Sphecidae)
(not immediately expressed as an overt response)
Conditioning [to nectar sources]
(Honey bee – Hymenoptera: Apidae)
Learning through Imprinting
(host fidelity and speciation – Diptera: Tephritidae: Rhagoletis pomonella)
hawthorns
apples
overlap
10