Syllabus
 Filter Feeding
 In Polychetes
 In Molluscs
 In Deuterosmia
 In Crustaceans
 Respiration
 Physical factors
 Pigments
 Gills and Lophophores in Polychetes
 Gills and Lungs in Molluscs
 Gills and Trachea in Arthropods
Filter Feeding
Remember
 This type is found only in aquatic animals
 It is disappeared from the terrestrial animals due
to the lower density of air
 It is occurred in small aquatic animals
 It takes place through special organs
Filter Feeding in Molluscs
 The better example occurs in bivalve (lamellibranch) molluscs
 They have become typically semi-sessile animals
 They inhabitants of sandy or muddy substrata
 Their alimentary system adapted for microphagy
 They have ciliated labial palps and ciliated gills (ctenidia)
 These structures have a good role during filter feeding and sorting
mechanism
Filter Feeding in Molluscs
 The structure and function of gills or ctinidis
 The elongated ctenidia of bivalves are two demibranchs, composed of a
parallel row of filaments
 These filaments differ among the protobanch, filibranch and
eulamellibranch.
 In protobranch, they are unfolded but in other two are folded forming
ascending and descending limbs.
 The adjacent filaments are jointed by ciliary junctions in filibranch and
are jointed by vascular interfilamental junctions in eulamellibranch.
 The gills are covered with frontal and lateral cilia.
Filter Feeding in Molluscs
 Lateral cilia draw water into the mantle
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chamber to the interlamellar and
suprabranchial cavities.
As the water passes between the filaments,
the food particles are filtered out by laterofrontal cirri (ciliary complex).
This ciliary complex consists of 20-25 pairs of
cilia, arranged as a double row and all
beating together at right angles to the long
axis of the gill filament.
The distance between adjacent cirri is about
2.0 to 3.5 m ( this space is still large)
therefore the cilia bend at regular intervals
along the cirrus so that they form a
meshwork between the cirri and also
between the adjacent filaments.
The particles are trapped by the laterofrontal cirri and thrown onto the frontal
cilia and entangled in mucus over the
surface of the gill lamellae.
These particles may pass either into a
ventral marginal groove or into a dorsal
groove and according the particle species,
the food material is carried to the two pair of
labial palps
Filter Feeding in Molluscs
 The structure and function of labial palps
 These are triangular structures, one pair lying on
either side of the mouth.
 They have a ciliary mechanisms
 They cover with fine cilia which are adapted for
conveying the fine particles required for food and
with coarse cilia dealing with the rejection of larger
particles means they have a sorting mechanism.
Filter Feeding in Molluscs
In Pecten and Ostrea :
 The gill lamellae are folded
and the cilia are beat on the
crests of the folds in a
differing way than that in
the grooves
 The smaller particles (food)
are carried upwards by fine
cilia to the dorsal groove
while the coarse particles
such as sand grains are
carried downwards and drop
off from the gill edge or
shaken off by muscular
movements of the
demibranchs.
Filter Feeding in Molluscs
 In Sabella
 The gills are divided into a deep channel lined by
fine cilia and superficial one lined by coarse cilia.
 Fine particles are carried into the bottom of the
groove whereas the coarser are conducted to its
edge.
Filter Feeding in Molluscs
In Ostrea :
 The labial palps are ciliated
 Their sorting function depends on the
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structures of their internal faces which
are crossed by series of diagonal folds.
These folds overlap each other in the
direction of the mouth.
The uppermost part of one fold is
covered by the next adjacent one.
The sorting mechanism is depend on
the weight and not on the size of the
particles.
The heavier particles are settle down
into the grooves between the slope of
one fold and under the influence of a
powerful ciliary current, they sweep
them to the upper margin of the palp.
The lighter particles are swept from
one slope to the next and pass towards
the mouth.