Nutrition in invertebrate

Mode of nutrition and feeding in invertebrate.



Feeding habits of animals varies from one from of

animals to another. Based on nutritional mode of

animal animals are group into:

Holozoic---Solid/semi solid foods are swallowed

both obtained from plants and animals. Eg

spnges,arthopodes.

Holophytic---Sythesised own food. Eg euglena

Saprophytes—Absorbed food from the dead

decaying materials. Eg Annelids

Coprozoic—obtain from dung and faecal matter eg

beetle

Parasitic—obtained by ectoparasitic and

endoparasitic mode.

Animals are also grouped into herbivorous,

carnivorous and omnivorous.



Protozoa

Feeds on diatoms and phytoplanktons and bacteria.

Holozoic in nutrition.

Ingest in various ways :

Circumvallation_cup formation

Circumfluance—amoeboic movement.

Import—filament sinks into cytoplasm

Digestion---digest within the vacuole

Absorption---by diffusion

Egestion --through opening like cytophage



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--through contractile vacuole





Sponges

Holozoic in nutrition, feeds on minutes organismsand

degenerating materials

Inner lining of spongocoel has layer of choanocytes

and has “collar”

Collar of choanocyte allows only the water to let out

and traps the food particles.

Water current bring the preys into the collar of

chaonocytes which is then traped partially digested

in the collar cell itself.

Later it is passed to ameboid cells in mesogleal

layer for thoroughly digested.digested food is stored

in the amoeboid cells.

Thus digestion is intra cellular digestion brought

about by two cells.



Coelenterata

Holozoic in nutrition, feeds on crustacean, insect

larvae and smaller animals.

During feeding organism normally remain

motionless tentacles trailing in water.

If prey is passed by the one of the nearest tentacle

releases poison through the cells (nematocyst)

‘expolsion”, chemical released would paralyze the

animal.



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Finally the tentacle wrapped around the prey and

contracts to draw the prey close to the mouth.

No. of tentacle involved in trapping prey depend on

stimulus of prey or food.

Digestion begins once it enters the gastrovascular (

enteron)via mouth.

Distilled region of endodermal cells have more

glands that secretes digestive juice, it reduces the

prey to smaller fragment.

Digestible food is the taken into vacuole by the

pseudopodial activity of endodermal cells.The

digestion is began in enteron leading extracellular

digestion like most higher group animals and

complete it digestion in endodermal cell thus

intracellular digestion like protozoa.

Undigested are returned to cell surface for exocytosis



Platyhelminthes

Parasatic mode of life.

Completely dependent to the digested food of host

Digestive of this animal are poorly developed like

planaria, well developed in liver fluke (feeds on host

muscles thus need to digestive system) and

completely absent in most of the animals like

tapeworm

Absorption of food by simple diffusion through body

surface.





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Nemahelminthes

Feeds on digested food of its host the food is suck by

muscular pharynx.

Digestion is extracellular in the intestine. Digested

food is absorbed by the intestinal cells

Digestive system is simple straight tube.

Has mouth and anus





Annelida

Holozoic, saprophytic and parasitic (sanguivorous

habit)

Feeds on small crustaceans worms, larvae and

decaying matters and blood etc.

Extracellular (digestion like nereis and herudinea)

inratcellular and intracellular digestion (earthworm)

are prominent features in annelida

Has a complete digestive system starting from mouth

to ends at anus for all the class of annelida

Digestive glands are found in the wall of the

digestive tract.

Has well developed pharyngeal gland.

Crop in leech and gizzard in earthworm for breaking

down the food, instead of stomach.



Arthopoda

Arthopoda shows great range of feeding habit.

This group of animals occupies wide range o habitats



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They are holozoic in nutrition, but majority of them

are omnivorous, carnivorous and cannibalistic (who

eats it same species).

They have well developed digestive system

Digestive gland is well developed and functional

even in larval stage.

Digested foods are reabsorbed into the haemocel

(coelomic fuid)

Digested food provide energy while some are store as

fat

Animals are well equipped with extra appendages for

catching the prey like chelated legs maxillipedes and

modified jaws are used for catching and directing

prey to the mouth.

Digestion is extracellular



Mollusca

Holozoic,havivorous and carnivorous some

omnivore.

They feed on small animals insects, fishes, planktons

and organic matter.

Mode of feeding is filter feeding.

Most bivalve collects their food by cilliary beating

Cilia are present in the gills filament

Food particles are directed towards the mantle cavity

The water current would lead toward the mouth.

Diffuse food into the blood and go into circulation





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Digestion is intra cellular(Amoeboid cells digest

food) and intercellular(cavity of alimentary canal).

Has well developed digestetive system.



Echinoderm

 Holozoic , carnivorous

 Feeds on crustaceans, mollusks and fishes.

 Has complete digestive system and digestive

gland (open in mouth and ends in anus)

 Has stomach, pyrolic duct extended into flexible

arm the form of pyrolic caecum

 Pour the digestive juice, once digested it

absorbed the food

 Absorbed food is further digested intracelluarly

and food is diffused int coelomic fluid.

 Coelomic distributes the food all over the body

 Has well developed digestive system

 Extratcellular digestion and intracellular

digestation



Generalization of feeding mechanism in

invertebrate



Generally the nutritional mode of different group of

invertebrate varies significantly in terms of feeding

ingestion, absorption and egestion.





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Mode of obtaining food becomes more complex and

specialized in higher groups of invertebrate.

Absorption of digested liquid forms of feed in lower

and solid and semisolid in higher group.

Digestive system is completely lacks in lower group

and found well organized digestive system in higher

vertebrate.

Digestion is normally intracellular to extracellular

from lower organism to higher groups.

Diffusion of digested food in lower vertebrate while

in higher the food digested is diffuse into the

haemocoel, through it it is distributed to all over the

body.

Trap their preys by pseudopodial extension, cilia and

tentacles movement or bodily movement in lower but

in higher have specialized organs like arms in

echinoderm and mollusks.







Reference:

Armugum N.. (2004). A text book of

invertebrate. Sara publication, new Delhi









Nemahelminthes/Aschelheminthe



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General characteristics:



1. They are vermiform animals

2. They are bilaterally symmetrical

3. Body covered with cuticle

4. They are pseudocoelomate animals

5. They are parasitic or free living

6. The have organ system grade of organization

7. Excretory organ like protonephridia are present

8. Elementary canal is straight and has mouth and

anus



Classification



Phylum has five class;

1. Rotifer---------------- Rotaria

2. Gastrotricha--------------Chaetonotus

3. Kinorhyncha-------------Echinoderes

4. Nematomorpha----------Nectonema



5. Namatoda--------------Ascaris

Lumbricoides(round worm),

a) Body is long, slender and large size round worm

b) Body has thick cuticle

c) Has sexual diamorphism

d) Digestive system is complete in adult





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e) Circulatory system, respiratory system, cilia are

completely absent

f) Excretory system consists of glandular organs

nervous system consists of circumenteric ring in

anterior and posterior end

g) They are dioecious; male is small than female

h) Male has ventrally coiled tail

i) Two penial specule is present

j) Fertilization is internal, and direct

k) Life cycle includes larval forms

l) They are parasitic in vertebrate









Annelida



General characters:

 Soft cylidtcal and enlogated body

 Bilaterally symmetrical body

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 Organ grade organization

 Body covered with cuticle

 Locomotion by the satae

 Circulatory system is closed type

 Excretory organ segmentally arranged nephridia

is present.

 Metamerically segmented body

 Biltareally symmetrical

 True coelomate,triplobastic



They are divided into 8 classes:

 Polychaeta----------------------Nereis(sand or claw

worm or rag worm) Oligochaeta--------------------

--Pheretema Posthuma (earthworm)

 Hirudinea-------------------------Hirudinaria

granulose(leech)

 Arcchiannelida

 Echiuroidea

 Sipunculoidea

 Priapulida

 Myzostomaria



Arthopoda:

General characteristics;

Body divided into three parts; head, thorax, and

abdomen

 2 pairs of Legs



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 2 pairs of wings

 Pair of Antenna

 Jointed legs

Divided into Five classes:

1. Merostomata

2. Arachinda------------------------Aranea(Spider),

Plamnaeus(scorpion)

3. Crustacean------------------------saccullina(root

headed barnacle), Penaeus(prawn)

4. Myriapoda-----------------------

Spiroatreptus(millipede),

Scolopendra(centipede)

5. Insecta----------------------------dragon fly, dung

beetle and stick insect.









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