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The Insect Respiratory System Tracheal System
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The Insect Respiratory System I. Structure
A. Spiracles
spiracles
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The Insect Respiratory System I. Structure
A. Spiracles 1. types of spiracles a.
simple b. atriate
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The Insect Respiratory System I. Structure
A. Spiracles 2. types of tracheal
systems a. Closed (apnuestic) no
spiracles b. Open with functional
spiracles
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The Insect Respiratory System I. Structure
B. Trachea
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The Insect Respiratory System I. Structure
B. Trachea 1. composition of tracheal
tube -- ectodermal origin outer epidermal
layer inner cuticle with taenidia
epidermis
Lumen of tracheal tube
cuticle
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taenidia
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The Insect Respiratory System I. Structure
B. Trachea 2. organization of tracheal tubes
Dorsal trunks
Lateral trunks
Ventral trunks
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The Insect Respiratory System I. Structure
B. Trachea 2. organization of tracheal tubes
cross section
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Dorsal trunks
Air sacs
spiracle
GUT
Visceral trachea
Lateral trunks
Ventral trunks
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The Insect Respiratory System I. Structure
C. Tracheoles arise from tracheol end cell
tracheoles
tracheal end cell
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Smaller trachea
Small trachea
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The Insect Respiratory System I. Structure
D. Air sacs
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Dorsal trunks
Air sacs
Visceral trachea
Lateral trunks
Ventral trunks
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The Insect Respiratory System I. Structure
D. Air sacs -- increase tidal volume of air --
decrease body mass
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The Insect Respiratory System II. Ventilatory
Processes A. Passive ventilation -- no
active pumping -- gases diffuse passively
into and out of spiracles
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The Insect Respiratory System II. Ventilatory
Processes B. Passive suction ventilation in
inactive insects and when in diapause --
spiracle valves closed, but not sealed valves
flutter and open for only brief bursts -- O2
diffuses from tracheoles into cells -- some CO2
diffuses into tracheoles but some moves into
hemolymph CO2 H2O ? H2CO3 ? H HCO3-
(bicarbonate
ion)
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The Insect Respiratory System II. Ventilatory
Processes B. Passive suction ventilation in
inactive insects and when in diapause --
results in net loss of gases from trachea
creates negative pressure inside tracheal
tubes -- air is sucked in passively through
fluttering spiracles ( passive
suction) -- CO2 reaches threshold conc. in
trachea -- spiracles stimulated to open
completely (burst) CO2 rushes out
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The Insect Respiratory System II. Ventilatory
Processes C. Active ventilation 1.
Process -- telescoping of abdomen or head
-- peristaltic waves of abdomen -- creates
pressure in hemolymph, which acts on
tracheal tubes and air sacs. -- controlled by
CPG in thoracic or abdominal
ganglion
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The Insect Respiratory System II. Ventilatory
Processes C. Active ventilation 2.
modifications a. One-way flow in
thoracic spiracles out abdominal spiracles
b. Cardiac reversal of Lepidopterans
Valve that can separate thorax from abdomen
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Cardiac reversal in Lepidopterans -- valve
closed partially separates thorax and abdomen --
reverse flow of blood in heart hemolymph pumped
from thorax into abdomen -- creates negative
pressure in thorax that helps to suck air through
thoracic spiracles increases air flow to flight
muscles
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The Insect Respiratory System III. Aquatic
respiration A. Cutaneous respiration
diffusion across body surface
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The Insect Respiratory System III. Aquatic
respiration B. Tracheal gills
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The Insect Respiratory System III. Aquatic
respiration C. Surface breathers 1.
hydrofuge breathing tube
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The Insect Respiratory System III. Aquatic
respiration C. Surface breathers 1.
hydrofuge breathing tube rat tailed maggot
Family Syrphidae
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The Insect Respiratory System III. Aquatic
respiration C. Surface breathers 1.
hydrofuge breathing tube water scorpion
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The Insect Respiratory System III. Aquatic
respiration C. Surface breathers 2. air
bubble
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The Insect Respiratory System III. Aquatic
respiration D. Submerged air breathers 1.
plastron functions as physical gill
Riffle area
Riffle beetle
Water boatman
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The Insect Respiratory System III. Aquatic
respiration D. Submerged air breathers 1.
plastron functions as physical gill 2.
oxygen taken from aquatic plants
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The Insect Respiratory System III. Aquatic
respiration E. Hemoglobin -- in some
aquatic insect larvae that live in
anerobic conditions -- binds with O2 when
abundant and then releases it slowly when
anerobic
Midge larvae