Pila is an amphibian that can perform both branchial and pulmonary respiration. When in water, it breathes through gills called ctenidia located in the branchial chamber. On land, it breathes through a pulmonary sac located in the pulmonary chamber. The pulmonary sac allows for gas exchange between air and blood. Pila can also respire underwater using a respiratory tube formed by its nuchal lobe to bring air into the pulmonary sac. Its osphradium organ helps detect chemicals in the water.

1. Shri Shankaracharya Mahavidyalaya, Junwani , Bhilai
Respiratory system of Pila
Dr. Sonia Bajaj
(Head of Department)

2. Introduction-
Pila is a amphibian. When it is in water, it will
perform branchial respiration with the help of
gill. When it is on land it will
perform pulmonary respiration with the help of
pulmonary chamber.
Respiratory organs- Branchial Respiration:
• When pila is in water it will perform
respiration with gill or ctenidium.
• 1. Ctenidium: It is present in the branchial
chamber. It is monopectinate gill. It looks
like a comb and is situated on the right side
of the branchial chamber hanging from its
dorsolateral wall.
• It consists of a long axis, the ctenidial axis
which remains attached to mantle wall.
Ctenidial axis contains two blood vessels an
afferent and an efferent.

3. Afferent blood vessel carries
deoxygenated blood from the gill to the
heart. Axis bears a long series of
triangular leaflets called lamella and
makes the actual surface of gaseous
exchange. Lamellae are highly
vascularized and in the middle they are
larger but smaller at both the ends.
Ctenidium is innervated by nerves from
the left pleural and supra-intestinal
ganglia. This nerve supply indicates that
it is actually an organ of left side but has
shifted to the right side during torsion.
Histologically, each lamella is formed of
a double layer of epithelium which
encloses a narrow cavity.
Each epithelial layer consists of
(i) non-ciliated columnar cells
(ii) ciliated columnar cells and
(iii) Glandular cells.

4. 2. Pulmonary sac:
It is developed from the mantle wall and hangs into the pulmonary chamber and opens
into mantle cavity through pulmonary aperture.
Dorsal wall of the pulmonary chamber is pigmented, while the ventral wall is creamy
white. These walls are muscular and highly vascular.
3. Nuchal lobe:
These are highly contractile structures of the mantle situated one on either side of the
head.

5. Mechanism of Aerial Respiration:
It takes place in two ways:
(i) In Water:
Pila can respire through the pulmonary sac while it remains in water. To inhale the
atmospheric air, it comes to the surface of the water. It then expands the size of the left
nuchal lobe, both in length and breadth and rolls up to form an elongated respiratory tube.
The outer end of the tube extends beyond the level of water and sucks in air from the
atmosphere. The inner end of the tube comes in contact with the opening of the pulmonary
sac. The alternate contraction and dilation of the mantle wall and the pulmonary sac help in
the process of respiration.
Following the exchange of oxygen and carbon dioxide, from air to the blood vessels of
pulmonary sac and from blood vessels to air, the expelled air goes out of pulmonary cham-
ber through the respiratory tube. During this exchange, the branchial chamber remains
completely separated from the pulmonary chamber by the epitaenia which comes in contact
with the roof of the mantle.
.

6. ii) On Land:
During dry season, when the water level gets reduced, or while living on land, Pila does
not use any respiratory tubes or siphons. The pulmonary sac directly becomes filled up
with atmospheric air to facilitate aerial respiration.
The shell remains closed completely with the help of operculum during the time of
aestivation, when Pila respires with the little amount of stored air kept in the pulmonary
sac. Hemocyanin, dissolved in plasma acts as the respiratory pigment in Pila.

7. Differences between aquatic and aerial respiration in Pila
Aquatic respiration1 Aerial respiration
Performed with the help of gills or ctenidia. Performed with the help of pulmonary sac.
Respiratory site is the branchial chamber or
the right cavity of the mantle.
Respiratory site is the pulmonary chamber
or the left cavity of the mantle.
Movements of cilia of the lamellae help in
the intake of water.
Contraction and relaxation of muscles of
pulmonary sac and mantle wall, help in the
intake of air.
Gaseous exchange takes place between the
water and blood.
Gaseous exchange takes place between the
air and blood.
It occurs when Pila remains in clean water. . It occurs when Pila remains either on land
or in dirty, shallow water.

8. Sensory Organs -
osphradium
Pila has a single gill-like osphradium in the left pulmonary area. It is used to detect
materials entering gills and hangs from the roof of the mantle cavity. In mollusk, a single or
paired sensory attachment to the visceral ganglia is called osphradium. The major
function of osphradium is to test the incoming water for silt and food
particles. The osphradium also acts as an olfactory organ in certain mollusks and is linked
with the respiratory organ Osphrodium structure resembles the feather of a bird and is also
called Bipectinate. Chemoreceptors are used to detect chemical changes in the
surroundings. It is found in the genus Conus- the cone snails and the predatory sea snails.

9. References-
Modern text book – R.L.Kotpal
Jantu Vigyan- S.M. Sexsena
Jantu Vigyan- Dr.H.N. Baijal