structure and function of insect respiratory system

SUBMITTED BY
S.NAGESH
TAM/2016-17

STRUCTURE AND
FUNCTION OF INSECT
RESPIRATION SYSTEM

RESPIRATION
A process of interchange of gases between
environment and the blood or cellular
tissues of organisms.
.Respiratory system is ectodermal origin.

GENERAL VS. INSECT RESPIRATION
GENERAL RESPIRATION INSECT RESPIRATION
 A process in living
organisms involving the
production of energy,
typically with the intake of
oxygen and the release of
carbon dioxide from the
oxidation of complex
organic substances.
 It is a complex network of
tubes (called a tracheal
system) that delivers
oxygen-containing air to
every cell of the body. Air
enters the insect's body
through valve-like
openings in the
exoskeleton.

 Keilin (1944) classified respiratory system of insects on the basis of the
number and distribution of the functional spiracles are :

1. Holopneustic: All functional (2 thorax & 8 abdomen). E.g. Grasshopper
2. Hemipneustic: 1 or 2 non-functional. E.g. larvae
3. Peripneustic: 9 functional – (1 in thorax & 8 in abdomen). E.g. Caterpillar
4. Amphipneustic: 2 functional - (1 Anterior &1 Posterior abdomen). E.g.
maggot.
5. Propneustic: 1 functional – (Prothorasic) . E.g. Puparium
6. Metapneustic: 1 functional – (last abdominal) . E.g. Wriggler
7. Hypopneustic: 7 functional (1 thorax & 6 abdominal) .E.g. head louse
8. Apneustic: All spiracles closed. E.g. Aquatic and Endoparasite.
9. Hyperpneustic: Presence of more than the normal spiracles.
E.g.Japygidae.
10.In collembola in smithurids one pair of spiracles present between head and
thorax
TYPES OF RESPIRATORY SYSTEM
REF- Insects Structure and Function- R.F.CHAPMEN

Holopneustic Metapneustic Apneustic
OPEN CLOSE
D
Cockroach Mosquito larvae Mosquito
larvae
May fly
larvae
Dragon fly

COMPONENTS OF RESPIRATORY
SYSTEM
 Spiracle
 Tracheae
 Tracheoles
 Tracheaoblast
 Air sacs

SPIRACLE
It is the external opening through which air enters
into the trachea.
Insects have about ten pairs of openings, called
spiracles, in their exoskeletons.
It has a chamber or atrium with a opening and
closing mechanism called Atrial valve.
spiracle is surrounded by a Sclerite called
Peritreme.
Closing and opening of spiracle is regulated by atrial
valve.
In dipterans coleopterans ,lepidopterans,spiracles
consists of sieve plate.
Peristgmatic glands present around the spiracle that
prevents the wetting of organs.

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.

TRACHEA
 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.

TRACHEOLES
It is less than 1 m in diameter and they endμ
blindly and closely contact the respiring
tissues.
Gaseous exchange occurs across
tracheoles.

TRACHEOBLAST
 The branches of tracheae end in polygonal
cells.
consist of Plasma lemma, Cytoplasm,
Nucleolus.

AIRSACS
 Balloon-like structures acts as oxygen reservoir.
Provide buoyancy to flying in aquatic insects.
In dry terrestrial environments, this temporary
air sacs allows an insect to conserve water by
closing its spiracles during periods of high
evaporative stress.
Air
sac

RESPIRATORY PIGMENTS
 Larval midges of the genus Chironomus, and
endoparasitic bot fly larvae in the genus
Gastrophilus have hemoglobins that enable
them to extract oxygen from extremely
hypoxic media.
The hemoglobin of Chironomus has two heme
groups, and is 50% saturated with oxygen at
less than 0.1 kPa, compared to more than 3
kPa in vertebrates.

TRACHEAL SYSTEM OF RESPIRATION

MECHANISM OF RESPIRATION
There are thus two distinct phases in the
transport of gases.
 one through the tracheal system known
as air-tube transport.
 one through the tissues in solution in the
cytoplasm, known as tissue diffusion.

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.

As carbon dioxide is more soluble, it is
present in much higher concentrations in the
blood and tissues than oxygen, generally in
the form of bicarbonate.
Carbonic anhydrase is required to quickly
convert bicarbonate to carbon dioxide, this
enzyme is reported to occur in the tissues but
not the blood.

CONVECTION
Convection is the bulk flow of fluid, driven by
a pressure gradient.
diffusion can suffice for gas exchange of
many insects, why is convection so common?
Theoretical studies have demonstrated that
use of convection rather than diffusion can
decrease water loss rates, even in small
insects.
 Insects produce compression of the air sacs
and tracheae in multiple ways. The best
understood is abdominal pumping.

Abdominal compression leads to a reduction
of body volume and a rise in hemolymph
pressure that causes expiration.
Expansion of the air sacs and inspiration
result from the reduction of pressure due to
the muscular or elastic expansion of the
abdomen.
Changes in abdominal volume may be
produced in various ways.
 Heteroptera and Coleoptera, the tergum
moves up and down.
 Odonata, Orthoptera, Hymenoptera
 and Diptera, both tergum and sternum move

Odonata,
Orthoptera,
Hymenoptera
and Diptera,
both tergum
and sternum
move and this
movement
may be
associated with
telescoping
movements
of the

DISCONTINUOUS GAS EXCHANGE
 The movement of oxygen into the tracheae and
carbon dioxide emission then 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.

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.

FUNCTIONS OF THE 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.
Traceoles involves in light emission in fire flies.

RESPIRATION IN AQUATIC INSECTS
Aquatic insects obtain oxygen
directly from air or from that
dissolved in water.

SPECIAL STRUCTURE
Respiratory siphon
Hydrofuge hairs
Air stores

RESPIRATORY SIPHON
Most aquatic insects obtain oxygen from air by
making frequent visits to the surface of water
or by having semi -permanent connections
(siphon) with the air.

E.g. Mosquitoes larvae
photobucket.com

HYDROFUGE HAIRS
The spiracles area develops special hairs having
a coating of non- wettable wax on one side
enabling the larvae to stay in the water surface
and expose their spiracles to the air.
They store air in the pile of erect hydrofuge
hairs.
It enables the insects to remain submerged in
water for longer time.

HYDROFUGE HAIRS
E.g. Culidiae
Mosquito larvae

AIR BUBBLES
 Some aquatic insects carry a bubble of air, whenever
they dive beneath the water surface.
 This bubble may be held under the elytra or it may be
trapped against the body by specialized hairs.
The bubble usually covers one or more spiracles so the
insect can "breathe" air from the bubble while submerged.

OXYGEN DISSOLVED IN WATER
CUTANEOUS RESPIRATION
In many aquatic larvae, even when tracheal
gills are present where the integument is
extremely thin, respiration is accompanied by
simple diffusion of gases through their skin.

CUTANEOUS RESPIRATION
E .g. Chironomus larvae

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.
Gills take an active part in respiratory activity
particularly in the summer months and when
water is poor in oxygen.

Lamellate gills - Mayfly naiad

Rectal gills - dragonfly naiad

Filamentous gills - damselfly naiad

BLOOD GILLS
Thin –blood filled sacs without tracheae
project from the exceedingly thin body
surface in some dipterans larvae .
They help in the absorption of water ,
inorganic ions and respiration.
E.g. Tricopteran and dipterans maggot.

SPIRACULAR GILLS
It is the extension of the cuticle surrounding a
spiracle and bearing a plastron connected to the
tracheal system by Aeropyles.

SPRACULAR GILLS IN PUPAE OF
DIPTERAN

RESPIRATION IN ENDOPARASITIC
INSECTS
Endoparasitic insects may obtain their oxygen directly
from the air outside the host or by diffusion through the
cuticle from the surrounding host tissues.
CAUDAL VESICLE
 In braconid larvae the hindgut is everted through the
anus to form a caudal vesicle.
 In some insects like Apanteles, it is relatively thin-walled
and closely associated with the heart so that oxygen
passing in is quickly carried around the body

E.g.Bracon brevicornis on Opisina arenosella.

In Cryptochaetum iceryae (Diptera), a parasite
of scale insects, there are two caudal
filaments, which in the third-instar larva are
ten times as long as the body and are packed
with tracheae.
These filaments often get entangled with the
host tracheae and so provide an easy path for
oxygen transfer.
 Chalcidid (Hymenoptera) larvae are connected
to the outside from the first instar onwards by
the hollow egg pedicel, which projects through
the host’s body wall.

PNEUMATISATION
 Immediately ofter ecdysis the tracheal system
will be filled with liquid after some time it
replaced by gas is called PNEUMATISATION.
 Chalcidid (Hymenoptera) larvae are connected
to the outside from the first instar onwards by
the hollow egg pedicel, which projects through
the host’s body wall.

REFERENCES
A text book on Insects Structure and Function by
R.F.Chapman.
INSECTA an introduction by
K.NRagumoorthi,V.Balasubramani.
Wikipedia.

structure and function of insect respiratory system

structure and function of insect respiratory system

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to structure and function of insect respiratory system

Similar to structure and function of insect respiratory system (20)

Recently uploaded

Recently uploaded (20)

structure and function of insect respiratory system