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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
 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 Polychetes
 The simple and good examples occur among the
polychaetes
 These worms are free-moving
 Macrophagous and microphagous
 Most have an eversible pharynx
 Pharynx is used for burrowing and feeding
Filter Feeding in Polychetes
 The simple and good example occur in Nereis
 It produces over its body surface a mucous secretion into a net which
protects the surface and forms temporary linings to burrows .
 Water can pumped through this net.
 Food particles collect in the mucus secretion in the bag and is swallowed
 This feeding mechanism have been aided by the presence of head
tentacles and palps
Filter Feeding in Polychetes
 The previous structure has given rise in sedentary
worms to tentacular outgrowths (gills or branchial
crowns)
 These structures use in respiration but they also
use in mechanisms for the collection and sorting of
food particles.
 These structures also produce mucus which
distributed over the ciliated surfaces
 This feeding mechanism have been aided by the
presence of head tentacles and palps
Filter Feeding in Polychetes
 The second example occurs in Terebellid worms
 Ciliary feeding mechanisms occur in the sedentary
polychaetes
 These worms live in permanent tubes in mud
 Food particles enter the mouth opening by
Extending the long ciliated tentacles from the head over
the surface of the substratum
 Food is trapped in mucus and swept along ciliated
grooves into the mouth

Filter Feeding in Polychetes
 The second example occurs in Terebellid worms
 Tentacles are highly mobile
 They vary at different pointes
 At one point a tentacle will be flattened to form a
zone of attachment
 Distal of this point the remainder of the tentacle
explores the substratum
 Proximal the attachment point, the surface of the
tentacle will be folded to form a ciliated groove in
which the food is propelled.
Terebellid
worms
Filter Feeding in Polychetes
 The third example occurs in Chaetopterus
 This worm lives in sand or mud a U-shaped tube
 There is no branchial crown
 There are three pairs of fans that are modified parapodia

Water is drawn through the tube by the beating of these fans
 There is another pair of outgrowths forms two wings in front
of the fans



They are pressed against the wall of the tube
They secrete mucus
Mucus is drawn backwards by cilia in a ventral groove to a conical
bag
 There is a small cup surrounded the conical bag


Food particles are strained out by this mucous bag
Food particles are rolled up into a pellet in the cup
Filter Feeding in Polychetes
 At intervals the secretory
process stops and the cilia
in the ventral groove move
in reverse
 Therefore the pellet of
food is transported from
the cup to the mouth and
swallowed.