INSECT BODY PLAN

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INSECT BODY PLAN AND EXOSKELETON
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Arthropod Lineages
3
Insect Body Plan
Tagmata
Head
Thorax
Abdomen
6 segments - sensory feeding

• 11 segments
• digestion reproduction

3 segments - locomotion
Total of 20 segments (primitively)
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Insect Body Plan
Tagmata
Head
Thorax
Abdomen
Cross section
tergum (notum)
pleuron
pleuron
sternum
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Insect Body Plan
tergum (notum)
pleuron
pleuron
sternum
Note The bits of exoskeleton (the pieces in the
puzzle) that make up the outer surface of an
insect are collectively referred to as
sclerites. Each surface of an insect has its own
sclerites which are referred to as tergites,
sternites and pleurites.
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Insect Body Plan
Segments
1) Primitive Condition (annelids, larval insects)
primary segment
primary segment
primary segment
longitudinal muscle
intersegmental fold
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Insect Body Plan
Segments
2) Intermediate Stage (hypothesized)
primary segment
primary segment
primary segment
longitudinal muscle
segmental sclerite
intersegmental sclerite
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Insect Body Plan
Segments
3) Third Stage (seen in Apterygota)
secondary segment
primary segment
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Insect Body Plan
Segments
3) Third Stage (seen in Apterygota)
secondary segment
primary segment
4) Final Stage (seen in Pterygota)
phragma
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Insect Integument (Exoskeleton)
Why are insects crunchy?
Outer epicuticle
Epicuticle
Inner epicuticle
cement
wax
oriented wax
outer epicuticle
Inner epicuticle (cuticulin)
procuticle
pore canal
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cement
wax
Insect Integument (Exoskeleton)
oriented wax
Wax Layers - Control of Water Movement
WATER IS RETAINED
WATER
WATER
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Insect Integument (Exoskeleton)
Why are insects crunchy?
Outer epicuticle
Epicuticle
Inner epicuticle
Exocuticle
Procuticle
Endocuticle
Schmidts layer
Epidermis
Basement membrane
Pore canals
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Insect Integument (Exoskeleton)
O C - CH2
O C - CH2
NH
NH
O
O
O
O
CH2OH
CH2OH
N - acetylglucosamine polymer
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Insect Integument (Exoskeleton)
O C - CH2
O C - CH2
NH
NH
O
O
O
O
CH2OH
CH2OH
N - acetylglucosamine polymer
CO
NH
CO
NH
CO
NH
NH
CO
NH
CO
NH
CO
NH
CO
CO
NH
CO
NH
CO
NH
NH
CO
NH
CO
hydrogen bonds
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Insect Integument (Exoskeleton)
microfibril
N - acetylglucosamine polymer
sheets of microfibrils
orientation of microfibrils changes
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Insect Integument (Exoskeleton)
Protein Matrix
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Insect Integument (Exoskeleton)
Cross linking of protein matrix
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Insect Integument (Exoskeleton)
Cross linking of protein matrix
OH
O
OH
OH
O
OH
OH
OH
Protein
Protein
CH2
CH2
CH2
Protein
C
Protein
CH2
CH2
CH2
CH2
N-acetyl dopamine
N-acetyl dopamine quinone
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Insect Integument (Exoskeleton)
kg/mm2
Tensile strength of sclerotized chitin (sclerotin)