Filter feeding mechanism in echinoderms and organs of respiration in crustaceans

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PAVITHRA M
DEPARTMENT OF ZOOLOGY
AVINASHILINGAM UNIVERSITY

• Animals such as Starfish, Sea-urchin, Brittle-star, Sea-
cucumber and Sea-lily comprises the phylum Echinodermata.
• They are marine and marked by certain characteristics such
as,
i. Radial symmetry
ii. Presence of skeleton consists of ossicles
iii. Presence of spines on the skin
iv. Presence of water vascular system, etc..
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FEEDING
• Echinoderms are carnivores. Their diet depends upon the
species.
• Some eat algae and others filter small bits of food from the
water.
• Others hunt actively for selfish and even smaller starfish are
eaten by larger starfish.
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What is Filter Feeding?
• It is the method of aquatic feeding by filtering out plankton or
nutrition suspended in water.
• It means the food which is suspended in the water is strained or
filtered from the water and eaten.
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• Smaller animals directly swallowed by mouth in to stomach.
• Sea lilies, basket stars and some brittle stars use their tube
feet on flexible arms to capture plankton that float on
ocean currents.
• By using the tube feet of arms sea stars opens the shell of
prey and keep under its mouth.
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ASTEROIDEA - STARFISH
• In star fish, water vascular system which is the functioning of filter feeding
mechanism also.
• It is peculiar to echinoderms and not present in any other mammal groups.
• The essential parts of the system are
1) Madreporite
2) Stone canal
3) Radial canals
4) Ring canal
5) Tiedmann’s bodies
6) Polian vesicles
7) Lateral canal
8) Tube foot
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Madreporite
• It lying on the aboral surface and provided with number of grooves and
furrows.
• This furrows are perforated by minute pores that merge in to collecting
canals.
• Thus collecting canals opens in to stone canal
Stone canal
• It is s-shaped canal and strengthened by a series of calcareous rings.
• Internally it is lined with the cilia and the end opens into ring canal
Ring canal
• It is a wide pentagonal ring-like vessels lying arround the mouth.
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Tiedmann’s Bodies
• There are 9 tiedmann’s bodies occur, which are
yellowish rounded glandular bodies. They produce
phagocytes.
Pollian Vesicles
• This are thin walled bladders with long and narrow
necks
• It serve as the store house of fluid in the water
vascular system
Radial Canals
• There are 5 radial canals, one entering each arm and
its end in to terminal canal
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Lateral canal
• This canal leads in to podium or tube foot
• Each canal is provided with a valve to prevent backward flow of fluid in to radial
canal.
Tube feet
• The tube feet is hollow, elastic thin walled closed cylinder
• It consists of upper sac ampulla, middle tubular podium and a terminal disc
sucker.
• Tube feet are used to capture the prey. The suckers are used to open the
shells of the molluscs
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• The suckers on the tube feet are especially important. When the starfish
finds prey it uses tube feet to capture it, then hold it close to its mouth.
Once the prey is close and secure, the starfish pushes it stomach out
through its mouth to digest the prey.
• If the prey is a creature with a shell, the starfish pushes its stomach
through a gap in the shell before beginning to secrete digestive enzymes
that break down flesh that is then absorbed by the stomach.
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ORGANS OF RESPIRATION
IN CRUSTACEANS
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• Crustaceans belong to the Phylum Arthropoda which is
aquatic and characterized by joint appendages
• They range from microscopic creatures to massive spider
crabs
• Shrimps, crabs, crayfish and lobsters are all crustaceans
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• The primary organ of the respiration is the
gills. It breathes oxygen as does other
creatures in the earth. As they are aquatic
creatures, they use the respiratory organs and
breath oxygen through the gills.
• The gills are very similar to lungs in the way
that they function. The major difference is that
gills pull oxygen from water not air.
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There are three sets of respiratory organs, such as
1) Branchiostegites or Gill covers
2) Epipodites
3) Gills or Branchiae
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Branchiostegites or Gill covers
• Each gill chamber is enclosed between the
branchiostegite on the outside and thoracic wall on the
inner side.
• This gill chamber opens on all side except dorsally.
• The inner lining of the branchiostegite are thin,
membranous and highly vascular containing blood
lacunae,
• so it provides the respiratory surface for the exchange of
gases.
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EPIPODITES
• There are three pairs of simple, leaf like and highly vascular
epipodites which are the outgrowth of coxal podomers of
three maxillipeds.
• The epipodites lie in the anterior part of the gill chamber
below the scaphognathite.
• This serve as respiratory organs like the primitive gills
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GILLS OR BRANCHIAE
• Gills are the primary respiratory organ of the prawn.
• There are eight gills or branchiae lying inside each gill chamber.
• Only seven of them are exposed at once on the removal of gill cover as the eighth lies
hidden beneath the dorsal part of secondary gill.
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Structure of Gill
• The gills are more or less crescentic in shape with a gradual increase in size from
anterior to posterior direction.
• The dorsal end of the gill projects into the antero-dorsal depression of the gill
chamber, while its ventral end lies close to the lower margin of the gill cover.
• Each gill has central axis, which is the base and provides the structural support for the
gill plates.
• In palaemon, all the gills are phyllobranch.
• The gill plates are larger in the middle but become gradually smaller towards the two
ends of the gill
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TYPES OF GILLS
Podobranch or Foot-gill
➢ Gill is attached to the coxa of an appendages.
➢ There is one podobranch attached to the coxa of each second maxillipede
Arthrobranch or Joint-gill
➢ Gill is attached to the arthrodial membrane connecting the appendages to the thorax.
➢ There are 2 arthrobranches attached to the arthroidal membrane of tird maxillipede.
Pleurobranch or Side-gill
➢ Gill is attached to the lateral wall of the segment having the limb.
➢ There are 5 pleurobranches attached to the lateral walls of the thoracic segments
bearing five walking legs
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REFERENCES:
• Ekambarnath ayyar, M., Ananthakrishnan, T.N., Manual of Zoology, vol I(2), 17-18, 363-
387.
• Nair, N.C., Leelavathy, s., et.al., (2014), A text book of invertebrates, saras publication,
620-633.
• Jordan, E.L., Verma, P.S., (1995) Invertebrate Zoology, S.Chand & Company Ltd, 625-627.
• https://www.ck12.org/biology/echinoderm-ecology/lesson/echinoderm-ecology-advanced-
bio-adv/
• http://echinodermsg.blogspot.com/2007/04/feeding.html
• https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0156408
• https://sciencing.com/do-crustaceans-breathe-8788458.html
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