1. ASSIGNMENT
on
Anatomy and Physiology of Respiratory System
(ENT.502 : INSECT ANATOMY AND PHYSIOLOGY )
Submitted By:
Gurpinder Singh
M.Sc. Entomology
L-2020-A-52-M
Submitted To:
Dr. Kamaljeet Singh Suri
(Principal Entomologist)
Dr. Anureet Kaur
Professor (Entomology)
3. INTRODUCTION
• Insects must obtain oxygen from their environment
and eliminate carbon dioxide respired by their
cells.
• This gas exchange occurs by means of internal air
filled tubes .
• Respiratory system of Insects is ectodermal in
origin.
• Unlike humans blood is usually not involved
in Respiration.
5. 1. Physical Phase
It includes Oxygen transport and removal of carbon
dioxide
2.Chemical Phase
It includes Oxidation of Carbhohydrates resulting in
formation of Carbon dioxide and water
8. Spiracle
• External opening , in their exoskeletons
present on lower side of Tergum .
• chamber or atrium with a opening and
closing mechanism called Atrial valve.
• surrounded by a Sclerite
called Peritreme.
• Peristgmatic glands present around the
spiracle that prevents the wetting of
organ.
Spiracle
9. Types of Spiracles
• Simple or non- Atriate: An opening with no lip closure or filter
chamber.
• Atriate with lip closure: Slit like apparatus with two movable
valves/lips.
• Atriate with filter-apparatus: Atrium is lined with tiny hairs.
10. Based on number and arrangement
of functional spiracles
A. Polypneustic : (at least 8 pair of functional spiracles
on each side of body )
1. Holopneustic:10 pairs, 2 in thorax and 8 in abdomen. e.g.
grasshopper
2. Hemipneustic: Out of 10 pairs, one or two non-
functional
3. Peripneustic: 9 pairs - 1 in thorax 8 in abdomen e.g.
Caterpillar
1 - Holopneutic
2- Hemipneustic
3-Peripneustic
11. Based on number and arrangement
of functional spiracles
B. Oligopneustic (1 or 2 pair of functional spiracles in
each side of the body )
4.Amphipneustic 2 pairs - One anterior, one posterior, e.g.
maggot.
5. Propneustic: 1 pair -anterior pair e.g. Puparium
6. Metapneustic: 1 pair - posterior pair e.g. Wriggler
4.Amphipneustic
5. Propneustic
6. Metapneustic
12. Based on number and arrangement
of functional spiracles
C. Hypopneustic:10 pairs - 7 functional (1 thorax
+6 abdominal), 3 non functional. e.g. head louse
D. Apneustic: All spiracles closed, closed
tracheal system e.g. naiad of may fly.
Mosquito larva mayfly naid Dragonfly naid
13. Based on number and
arrangement of functional spiracles
E. Hyperpneustic : contains 11 pairs of spiracles (2 pairs in mesothorax ,
1 pair metathorax, 8 pairs in abdomen )
Ex. Diplura (Japygids )
IN quiescent stage , only 1st and 10th spiracle is open (Amphipneustic)
14. Tracheae
The tracheae are the larger tubes of the
tracheal system.
Ectodermal in origin.
Consist of epithelial cells (ectotrachea) and
cuticular lining called INTIMA.
Helical folds of cuticular lining – TAENIDIA.
Cuticular lining – Intima – shed along old
cuticle during molting
15. TRACHEOLES
• It is less than 1 micrometer in diameter
• end blindly and closely contact the respiring tissues.
• Gaseous exchange occurs across tracheoles.
16. Differences between trachea and tracheoles:
Trachea Tracheoles
• These are large tubes running from
spiracles
• Fine tubes arising distally from trachea
• Intima layer is shed during moulting • Intima layer is retained, unchanged
during moulting
• Never become intracellular • Intracellular
18. AIRSACS
• In trachea thin walled ,
balloon-like structures
acts as oxygen reservoir.
(where taenidia is absent )
19. Functions of Air Sacs
• Provide buoyancy to flying & aquatic insects.
• In dry terrestrial environments , it allows an insect to conserve
water by closing its spiracles during periods of high
evaporative stress.
• Act as sound resonater and heat insulator
• Provide space for growing organs
20. • Collembola , Archaeognatha have tracheae from each spiracle form a
tuft which remains separate from the tufts of other spiracles.
• In the majority of insects, however, the tracheae from neighboring
spiracles join to form longitudinal trunks running the length of
the body.
22. Air flow types
Two types
• Tidal (in and out of the same spiracles)
• Directed (inflow through anterior spiracles and outflow through posterior abdominal
ones.)
• Interconnecting longitudinal and transverse tracheal trunks make directed flow possible
and more efficient than tidal flow, because the system is constantly flushed and incoming
air is not mixed with used air.
23. Moulting of Tracheal System
• During moulting , Intima layer of Trachea is shed while of tracheoles
remains intact.
• Prior to the molt, the epithelial layer of the tracheae increases in size
• A new cuticle is formed under the old cuticle.
• Molting fluid fills the space between the new and old cuticle, and the old
cuticle detaches
• . The old cuticle is pulled out of the tracheae through the spiracles with the
rest of the exuvia, and the molting fluid is reabsorbed.
24. Functioning of
Repiratory
System
The spiracles of most terrestrial insects
have a closing mechanism, which is
important in the control of gas
exchange and internal pressures.
Opening and closing of Spiracles :
• Goverened by valves
• Generally opened due to elasticity of the cuticle
but during flight it opens due to sepration of
mesepimeron and metepisternum.
25. A one-muscle spiracle; second thoracic spiracle of a locust (Schistocerca) (after Miller, 1960a). (a)
External view; (b) internal view; (c) diagrammatic section through the spiracle showing how movement
of the mesepimeron (arrow) causes the valves to open wide (dotted).
26. Control of
Spiracle
opening
• By CNS (Central Nervous System) & local Stimuli
• If dry conditions , spiracle remain closed for long
time.
28. Diffusion
• Net movement of atoms or molecules
from high concentration to low
concentration is known as diffusion.
• Rate of diffusion inversely proportional to the
square root of the molecular weight of the
gas, so that in air, oxygen, with a molecular
weight of 32, diffuses 1.2 times faster than
carbon dioxide, with a molecular weight of 44
.
• Due to its greater solubility, the permeability
constant of carbon dioxide in the tissues is 36
times greater than that for oxygen
29. Ventilation
• Change in volume of tracheal system is known as ventilation
• Simple Diffusion – In smaller or less active Insects
• Ventilation – Large and Active insects ex. Grasshopper
• Ventilation done by Contraction of muscles in the abdomen and air is
forced out of trachea. As muscles relax, abdomen springs back to
normal volume and air is drawn in .
• Large Air sacs attached to Tracheal tubes increase the effectiveness
of this bellow like action.
30. Fluttering
• In some lepidoptera larvae , pupae and some coleoptera .
• Carbon dioxide is not released continuous but produced in
bursts followed by long interval in which very little carbon
dioxide is liberated although uptake of Oxygen is continuous.
• Advantage : Save water by closing the spiracles
31. PNEUMATISATION
• The process of replacement of liquid by gas in the tracheal
system is known as PNEUMATISATION
• Immediately after ecdysis the tracheal system will be filled
with liquid after some time it replaced by gas is called
PNEUMATISATION.
32. DISCONTINUOUS GAS
EXCHANGE
• The movement of oxygen into the tracheae and carbon dioxide
emission occur in discrete bursts when the spiracles
open; relatively little gas exchange occurs while they are closed.
This phenomenon is known as discontinuous gas exchange
discontinuous ventilation.
• It is common in adult insects when they are inactive at moderate to
cool temperatures, that is, when their metabolic rates are low.
• The pupae of many insects also exhibit DGE.
33. VARIATION
IN GAS
EXCHANGE
Higher metabolic rates demand higher
levels of oxygen intake. This is most
obvious in flight, when metabolic rates
can rise 5–30 fold.
GAS EXCHANGE IN FLIGHT: The massive
increase in oxygen consumption that
occurs when an insect flies requires a
greatly increased airflow through the
tracheae to the flight muscle.
34. RESPIRATORY PIGMENTS
• Larval midges of the genus Chironomus
• Endoparasitic bot fly larvae in the genus Gastrophilus have
haemoglobins that enable them to extract oxygen
from extremely hypoxic media.
35. Gaseous exchange in aquatic insects
Aquatic insects obtaining oxygen directly from the air or from the
dissolved oxygen in water.
A. Oxygen from air
B. Oxygen from water
C. Insects subject to occasional submersion
36. A. Oxygen from air
• Insects make frequent visits to water surface for acquiring Oxygen .
Prevent water entry into spiracles by
I. Possess hydrofuge properties around spiracles
II. Production of oily secretion by perspirucular glands
III. Hydrofuge properties around the spiracle are associated with hairs
Some have
I. Semi Permanent connection with air {thus insect remain submerged ex. Larvae of Hoverfly, Eristalis (Diptera)}
II. Thrusting Spiracle into Arenchyma of aquatic plants
III. Air Bubble
37. Hydrofuge properties
around the spiracle are
associated with hairs.
• When submerged ,hairs close
over spiracle, preventing entry of
water
• At surface , hairs separated by
tension forces, spiracle exposed .
• Ex. Notonecta (Heteroptera )
38. • Thrusting Spiracle into Arenchyma of aquatic plants .
• Ex. Chryogaster and Notophila (Diptera )
• Semipermanent connection with the aerenchyma of a
plant. The respiratory siphon of a mosquito larva
(Mansonia) which connects with the aerenchyma of
aquatic plants (after Keilin, 1944).
(a) Lateral view showing saw which cuts into the plant
tissue and recurved teeth which hold the siphon in place.
(b) Longitudinal section showing a terminal spiracle and a
trachea.
39. Contact Angle
• When a liquid rests on a solid or a
solid dips into a liquid, the liquid–air
interface meets the solid–air interface at
a definite angle ; that is constant for the
substances concerned.
• This angle, measured in the liquid, is
known as the contact angle .
• A high contact angle indicates that
the surface of the solid is only wetted
with difficulty; such surfaces are said
to be hydrofuge.
40. Gas
exchange
via air
bubbles
• Some insects carry a bubble of air down into the
water when they dive.
• The spiracles open into this bubble, so that it
provides a store of additional air.
• The position of the store is characteristic for each
species:
Ex. In Dytiscus (Coleoptera), it is beneath the elytra
• As oxygen is consumed, the bubble decreases in
size.
41. .
• As the insect dives, the gases in the
bubble are in equilibrium with those
dissolved in the water.
• As the insect uses oxygen, the equilibrium
is perturbed. It is restored by the inward
movement of oxygen and
the outward movement of nitrogen. This is
a continuous process; it is shown as two
separate steps for clarity.
• Note that carbon dioxide produced by the
insect is immediately dissolved in the water.
Oxygen comes out of solution faster than
nitrogen goes in.
• The bubble shrinks continuously as
nitrogen goes into solution
Diagram of an air bubble acting as a physical gill.
42. B. Oxygen from water
Closed Tracheal System:
TRACHEAL GILLS : The immature stages of many aquatic insects lack a
distinct communication with the exterior, the spiracle being closed or absent .
• In such insects there is an extensive network of fine trachea beneath
the integument, either concentrated in some regions or distributed all over as
in tracheal gills of immature stages.
• Lamellate gills/ Abdominal gills - mayfly naiad
• Filamentous gills - damselfly naiad
• Rectal gills - dragonfly naiad
44. Plastron respiration
• Insects have specialized structures holding a permanent
thin film of air on the outside of the body. This is known as
Plastron.
• Tracheae open into it so that oxygen can pass directly to
the tissues.
• In adult insects the plastron is held by a very close hair pile
in which the hairs resist wetting because of their
hydrofuge properties and their orientation.
• The most efficient resistance to wetting would be achieved
by a system of hairs lying parallel with the surface of the
body
• Ex. Aphelocheirus
Aphelocheirus
45. C. Insects subject to occasional submersion
Spiracular gills : A spiracular gill is an extension of the cuticle surrounding a spiracle
and bearing a plastron connected to the tracheal system by aeropyles.
• In water, the plastron provides a large gas–water interface for diffusion, while in
air the interstices of the gill provide a direct route for the entry of oxygen, and
water loss is limited because the gill opens into the atrium of the spiracle.
• Thus, in air, water loss through the spiracles is scarcely greater than in terrestrial
insects.
46. Spiracular gills of a pharate adult cranefly (Taphrophila)
. (a) Diagram showing basic structure and connection of gill to the tracheal system; the two left-hand branches
represent the gill as seen from the outside; the remainder have the upper layer of cuticle removed to show the
extent of the atrium.
(b) Transverse section through a gill branch.
(c) Detail of a plastron line.
47. Gas exchange in endoparasitic insects
• Endoparasitic insects may obtain their oxygen
1. directly from the air outside the host or
2. by diffusion through the cuticle from the surrounding host tissues.
• Diptera depend entirely on cutaneous diffusion
• Braconid larvae the hindgut is everted through the anus to form a caudal
vesicle.
48. Functions Of Respiratory System
• Provide the cells and tissues with oxygen.
• To eliminate carbon dioxide a product of respiration.
• It gives some degree of buoyancy in aquatic insects in phantom midge Chaoborus(Diptera).
• Hemolymph circulation.
• Act as connective tissues and binds the organs together.
• Air sacs allow growth of the body.
• Tracheal system involves In sound production in Gromphodorrhina (Blattodea) by forcing air
through the spiracles.
• Air sacs also helps as heat insulators and to maintain body temperature.
• Tracheoles involves in light emission in fire flies.
49. References
• The Insects Structure and Function FIFTH EDITION R. F. CHAPMAN
• Handbook of Entomology by T.V. Prasad
• Insecta An Introduction by K.N. Ragumoorthi , V. Balasubramani, M.R. Srinivasan, N. Natarajan)
• ENTOMOLOGY REFRESHER by Viji C.P. K. Phani Kumar
• http://www.dynamicscience.com.au/tester/solutions1/biology/respiratory/insectresp.html
• https://acis.cals.arizona.edu/community-ipm/community-ipm-output/publications/publications-view/mosquitoes
• https://www.kqed.org/science/341205/natures-scuba-divers-how-beetles-breathe-underwater
• https://www.sciencephoto.com/media/367844/view/water-scorpion
• https://scrubmuncher.wordpress.com/2011/08/09/lift-off/
• https://www.giand.it/diptera/morph/?id=48&lang=en
• https://www.freeexamacademy.com/movement-in-and-out-of-cells
