1) Respiration in non-chordate animals occurs through diffusion or specialized respiratory organs depending on the species. Single-celled organisms rely on diffusion, while sponges also use diffusion and water circulation. 2) Invertebrates like worms, insects, and arthropods use structures like trachea, book lungs, and gills for respiration. Trachea are a branching tube system that deliver oxygen to insect tissues. Book lungs are found in some spiders and scorpions. 3) Molluscs generally use gills called ctenidia. Echinoderms rely on diffusion through tube feet extensions, while some develop dermal branchiae. Respiratory pigments like hemoglobin

1. Physiology of respiration in Non chordate
Dr. Sonia Bajaj
Assistant Professor
Department of Zoology
Shri Shankaracharya Mahavidyalaya ,Junwani ,Bhilai

2. INTRODUCTION
• The Process of gas exchange in the body, called respiration.
• The act of inhaling and exhaling air in order to exchange oxygen for
carbon dioxide
• The process of inhalation of oxygen and exhalation of carbon dioxide is
known as respiration.
• There are two types of cellular respiration aerobic and anaerobic. One
occurs in the presence of oxygen (aerobic), and one occurs in the
absence of oxygen (anaerobic).
PROTOZOA
Single-celled organisms, such as bacteria and protozoa, are in
constant contact with their external environment. Gas exchange
occurs by diffusion across their membranes. The respiratory
gases may diffuse in and diffuses out trough the general body
surface, there are no special organ for respiration.

3. PORIFERA In sponges,
• The special respiratory organs are absent.
• •Gaseous exchange occurs by simple diffusion between the
cells of sponges and the current of water.
• Oxygen dissolved in water is taken in by diffusion through the
general body surface and carbon di oxide is given out.
• Amoebocytes distributes oxygen with in the mesenchyme and
carry away carbon di oxide.

4. COELENTERATES
• In coelenterates, the special respiratory organs are
absent.
• Their body cells are more or less directly exposed to
the environment, both cell layers absorb oxygen from
and expel carbon dioxide into the surrounding water.
• The oxygen is absorbed into their first layer of skin,
called the ectoderm.
• It goes through to the second layer, called the
endoderm. The oxygen molecules are used and
excess oxygen is released as carbon dioxide.

5. ASCHELMINTHES AND PLATYHELMINTHES•
• Respiratory organs are absent.
• The body walls of aschelminthes are very thin and thus it acts
as their respiratory system.
• In living flatworms and roundworms, the exchange of gases
takes place through general body surface.
• In parasitic form, there is no exchange of gases. Endo
parasites lives in almost oxygen free environment and fulfills
its relatively less energy requirements by anaerobic
respiration .
• Flatworms are small, literally flat worms, which 'breathe'
through diffusion across the outer membrane. The flat shape
of these organisms increases the surface area for diffusion,
ensuring that each cell within the body is close to the outer
membrane surface and has access to oxygen.

6. ANNELIDA
• Respiration in annelids occurs primarily through their moist skin,
although certain species have evolved specialized gills or use
paired projections called parapodia in gas exchange.
• In earthworms the respiration mainly occurred or performed
through skin the called as cutaneous respiration.
• The blood of earthworm contains a respiratory pigment –
Hemoglobin in a dissolved state in its plasma.
• The epidermis of the body wall acts as a permeable membranes
through which the atmospheric oxygen diffuses in its capillaries
and combine with haemoglobin to form oxyhaemoglobin.
• The oxyhaemoglobin is circulated by blood into the tissues where
oxygen tension is very low and carbon di oxide tension is high.
• The oxyhaemoglobin breaks up to release oxygen to the tissues
and haemoglobin in a reduced state •
• Now carbon di oxide from tissue diffuses into the blood due to its
high tension.
• The carbon di oxide is carried by the blood generally in a dissolved
condition and when it reacts to the epidermal capillaries it diffuses
from the blood to the atmosphere due to low tension.

7. ARTHROPODA
• Aquatic arthropods possess gills for respiration and are
covered by the exoskeleton, which is thin in this area and not
a barrier to the exchange of gases.
• Terrestrial arthropods possess tracheae and book
lungs(Spiders) as respiratory organs. The small, external
openings (spiracles) reduce water loss, the chitinous lining
prevents collapse •
• Book lungs are chitin-lined internal pockets containing
many blood-filled plates over which air circulates.
• Most spiders possess tracheae and book lungs, but large
spiders (such as tarantulas) and scorpions possess book
lungs alone.
The respiratory system of cockroach is very well developed to
compensate the absence of respiratory pigment in the blood •
Ten pairs of spiracles or stigmata are present on the lateral side
of the body. The largest first pair is present on the mesothorax.
The second pair is on the metathorax and the rest eight pairs
are on the first eight abdominal segments. • the haemocoel
contains a network of elastic, closed air tubes or tracheae.
Three longitudinal tracheal trunks are present on each side of
the abdominal cavity.

8. Respiratory organs of invertebrates
Trachea
• This respiratory organ is a hallmark of insects.
• It is made up of a system of branching tubes that deliver oxygen to, and remove carbon dioxide from, the tissues.
• The smallest tubes, tracheoles, penetrate cells and diffuse water, oxygen, and carbon dioxide.
• Tracheae are a system of tiny tubes that permit passage of gases into the interior of the body.
• Tracheal systems are highly efficient for these small, terrestrial animals.
• The pores to the outside, called spiracles, are typically paired structures, two in the thorax and eight in the abdomen.
Periodic opening and closing of the spiracles prevents water loss by evaporation.
Gills
• Many invertebrates use gills as a major means of gas exchange.
• Gills are branching organs located on the side of heads that have small blood vessels called capillaries. As the organism
opens its mouth, water runs over the gills, and blood in the capillaries picks up oxygen that’s dissolved in the water.
• Gills consist of plate-like structures called filaments that are covered by an array of lamellae enclosing a capillary blood
network.
• Oxygen-rich water passes through the narrow channels formed by the lamellar layers, where oxygen diffuses into the
capillaries. The densely packed lamellar structure is advantageous because it provides a large surface area for oxygen
transfer.

9. Book lung
• It is a form of respiratory organ found in certain air-breathing arthropods (scorpions and some
spiders).
• Each book lung consists of a series of thin plates that are highly vascular (i.e., richly supplied with
blood) and are arranged in relation to each other like the pages of a book.
• These plates extend into an internal pouch formed by the external skeleton that opens to the
exterior by a small slit. This provides an extensive surface for the exchange of oxygen and carbon
dioxide with the surrounding air. There are four pairs in scorpions and up to two in spiders.
Book gills
• It is believed that book lungs evolved from book gills. Although they have a similar book-like
structure.
• book gills are external, while book lungs are internal. Both are considered appendages because
book lungs develop from limb buds before the buds flatten into segmented lamellae.
• Book gills are still present in the marine arthropod Limulus (horseshoe crabs) which have five
pairs of them.
• The flap in front of them being the genital operculum which lacks gills.

10. MOLLUSCA
• In land snails and slugs, mantle cavity has evolved into
primitive lung .
• All molluscs breathe by gills that are called ctenidia (comb-
gills) because of their comb-like shape.
• A ctenidium is shaped like a comb or a feather, with a
central part from which many filaments or plate-like
structures protrude, lined up in a row .
• The mantle cavity forms a pulmonary chamber, the inner
surface of which is highly vascularized.
• Many molluscs have a siphon which expels water and
wastes.

11. ECHINODERMS
• In echinoderms (starfish, sea urchins, brittle stars), most of
the respiratory exchange occurs across tube feet (a series
of suction-cup extensions used for locomotion).
• Echinoderms typically breathe and respire by the simple
diffusion of gases like oxygen and carbon dioxide in and
out of their body cell membranes.
• this exchange is supplemented by extensions of the
coelomic, or body-fluid, cavity into thin-walled “gills” or
dermal branchiae that bring the coelomic fluid into close
contact with seawater.
• Respiratory tree is the branches of cloaca just inside the
anus with the help of the drawing water through the anus
and then expelled.

12. Respiratory Pigments in Invertebrates
In most animals have developed respiratory pigments. In general, respiratory pigments are
coloured proteins that contain a metallic element in their constitution and have the property of
forming loose combination with oxygen and sometimes with carbon dioxide.
Four different (biochemically) respiratory pigments are recognized – haemoglobin, chlorocruorin,
haemocyanin, and haemerythrin.
Haemoglobin: It is the most efficient respiratory pigment. It is widely distributed in the animal kingdom, starting
from some protozoa like Paramoecium to almost all vertebrates except eel larvae and some Antarctic fishes. Some
invertebrate phyla viz., Porifera, Cnidaria and Ctenophora, totally lack it.
Haemocyanin: Among various copper- proteins occurring in nature, only haemo cyanin can reversibly combine
with oxygen and thus, serves as a transport pigment. It is found in Chitons, some gastropods and cephalopods
amongst the molluscs and in crustaceans and Limulus amongst the arthropods. It always remain dissolved in the
plasma.
Chlorocruorin: This green coloured metalloprotein is found in the plasma of certain polychaet families. It is a
metalloprotein with the metal being iron (Fe++); the metalloporphyrin is similar to heme of haemoglobin except
that one vinyl (CH = CH2) group is replaced by formyl (0=CH) group in Chlorocruorin. The porphyrin is called
chlorocruoheme.
Haemerythrin: This cadmium-binding protein, containing respiratory pigment in the blood of various chiefly
marine invertebrates .

13. Functions of respiration
• Delivers oxygen to the cells in your body.
• Removes waste gases, including carbon dioxide, from the body when you exhale.
• Breathing – movement of air • Sound Production • Olfaction, or Smelling, Is a Chemical
Sensation

14. References
• A textbook of chordate-H.S. Bhamrah & kavita Juneja
• Invertebrate Zoology-P.S. Dhami & J.k. Dhami
• Modern text book of Invertebrate-R Kotpal
• Invertebrate Zoology 14 edition-Jordan & Verma