Digestive system of fish

1. DIGESTIVE SYSTEM OF FISH
OCN-1207 Marine Vertebrate

2. PresentedBy
Group 1 Group 8
1. Samsun Naher
BKH1718001F
2. Bibhuti Chakma
ASH1818037M
3. Rahmat Ullah
ASH1818047M
4. Tanvir Hyder Shishir
ASH1818057M
5. Tanzim Akter
BKH1818069F
1. Zahid Hasan
ASH1818036M
2. Imtiaz Hossain
ASH1818046M
3. Sanjida Akter Nisa
BKH1818056F
4. Israt Mehe Jabin
BKH1818067F
5. Jannatul Kubra Afrin
BKH1818077F

3. Digestion
• Digestion is the process of modifying and/or hydrolyzing
feed and food polymers into molecules and elements that can
be absorbed across the intestinal wall.
• In fish digestion, fish ingest food through the mouth and
break it down in the esophagus.
• The intestine completes the process of digestion and nutrient
absorption.
• Feeding is the first process of digestive system.

4. Digestive system
• Digestive system is the system by which ingested food is
acted upon by physical and chemical means to provide the
body with absorbable nutrients and to excrete waste
products; in mammals the system includes the alimentary
canal extending from the mouth to the anus, and the
hormones and enzymes assisting in digestion.
• The structural components of a fish's digestive system
include the mouth, teeth and gill rakers, esophagus, stomach,
pylorus, pyloric caeca, pancreatic tissue (exocrine and
endocrine), liver, gall bladder, intestine and anus.
• A fish's digestive system is adapted to their food habits.

5. Feeding mechanism
• Aquatic feeding mechanisms face a special difficulty as
compared to feeding on land, Because the density of water is
about the prey tends to be pushed away when the mouth is
closed.
• Types of Mechanisms:
Filter feeding
Ram feeding
Suction feeding
Protrusion
Pivot feeding

6. Filter feeding
• In filter feeding, the water flow is
primarily generated by the organism
itself, for example by creating a
pressure, by active swimming, or by
ciliary movements.
Krill feeding under high
phytoplankton concentration

7. Ram feeding
• Ram feeding, also known as lunge
feeding, is a method of feeding
underwater in which the predator
moves forward with its mouth
open, engulfing the prey along with
the water surrounding it.
Foraging Manta alfredi ram-feeding,
swimming against the tidal current with its
mouth open and sieving zooplankton from
the water.

8. Suction feeding
• Suction feeding is a method
of ingesting a prey item in
fluids by sucking the prey
into the predator's mouth.
• This is typically
accomplished by the
predator.

9. Lunge feeding
• Baleen whales feed on plankton
by a technique called lunge
feeding. Lunge feeding could
be regarded as a kind of
inverted suction feeding, during
which a whale takes a huge
gulp of water, which is then
filtered through the baleens.
School of adult Indian mackerel ram
feeding on macroplankton
Herring ram-feeding on a school of copepods

10. Protrusion
• Protrusion is the extension of the
mouth or premaxilla towards the
prey, via mechanical linkages.
Protrusion is known only in
modern bony fishes, which
possess many forms of coupled
linkages in their head.
catching prey by protruding its jaw

11. Pivot feeding
• Pivot feeding is a method to
transport the mouth towards
the prey by an upward turning
of the head, which is pivoting
on the neck joint.
Seahorses rely on stealth to ambush small
prey such as copepods. They use pivot
feeding to catch the copepod, which
involves rotating their snout at high speed
and then sucking in the copepod.

12. On the basis of feeding habits, the fishes
are categorized-
1. Herbivorous
2. Carnivorous
3. Omnivorous
4. detrivorous

13. • Herbivorous
• Herbivorous consume about 70%
unicellular Algae, Filamentous algae
And Aquatic plants.
• Herbivorous fishes have long and
coiled intestine.
• Carnivorous
• The fishes in contrast to Herbivore
have shorter gut, the intestine is
straight, very little coils are present.
• Some of the carnivorous possess
intestinal caecae.
Parrotfish
Barracuda

14. • Omnivorous
 Omnivorous fishes are consuming both
plant & animals.
 There gut length intermediates between
carnivourous & herbivouras.
• Detrivorous
 They consume detrivorous alone
with zooplanktons and
phytoplanktons.
 The arrangement of gill rakers are
such that it filters them from water.

15. The fishes can also be named on the basis
of modification of buccopharynx
1. Predator
2. Grazers
3. Strainers
4. Suckers
5. Parasitic

16. 1. Predator
 They possess well developed grasping and holding teeth.
2. Grazers
 They takes the food by bite. These fishes feed on plankton and
on bottom organisms.
3. Strainers
 They have effective straining or filtering adaptation due to the
aregment of gill rakers forming sieve for straining the food
material.
4. Suckers
 The fishes have inferior mouth and sucking lips.
5. Parasitic
 Almost fishes , the deep sea eel

17. BUCCOPHARYNX
AND
ITS MODIFICATION
Non-tubular part

18. Non-tubular Part of Buccopharynx
 The Non-tubular part of alimentary canals are-
Jaws
Mouth
Boccopharynx
Pharyngeal organ
Gill rakers

19. Jaws & Mouth
• The jaws hold the mouth.
• The main function of the
jaws in vertebrate is
helping in biting of food.
• In Fishes with suckers, the
lips are mobile and plicate
having fold or papillae. The
mouth in some fishes is
elongated as beak.

20. Mouth Structure
of Fishes

21. Mouth Structure
of Fishes

22. Buccopharynx
• These modification are-
Teeth
Pharyngeal pad
Gill rakers

23. Pharyngeal Organ
• It has two parts –
• A Caudal
• A blind sac

25. Gill rackers
• The gill rackers in both the
cartilaginous and bony fishes
have undergone specialization
for feeding.
• The gill rackers allow the soil
food to go to- gullet only water
is allowed to pass through gills
to outside.

26. BUCCOPHARYNX
AND
ITS MODIFICATION
Tubular part

27. Esophagus
Esophagus is the part of the alimentary canal which connects
the throat to the stomach. In humans and other vertebrates it
is a muscular tube lined with mucous membrane.
The esophagus and stomach are separated by external
constriction.

28. Stomach is the internal organ in which the major part of
the digestion of food occurs, being (in humans and many
mammals) a pear-shaped enlargement of the alimentary
canal linking the oesophagus to the small intestine.
The predatory and carnivore fishes have stomach.
The cyprinidae family has no stomach but possesses
intestinal bulb.
Stomach

29. Division of Stomach
a) Esox I Shape
b) Anguilla J Shape
c) Raja U Shape
d) Cottus V Shape
e) Mugil Y Shape
CS- Cardiac stomach; I- intestine; M- mascle;
PS- pyloric stomach O- oesophagus

30. Intestine
• The intestines of fish consist of two segments, the small
intestine and the large intestine.
• The small intestine is further divided into the duodenum
and other parts.
• Provisory the proximal part of the intestine is known as
duodenum, the middle, the ileum while the distal end is
rectum.
• Intestine in fishes one continuous organ and its parts are
usually differentiated histologically one by gradual
changes in the nature of mucosal layers.

31. Intestinal caecae
• Fish caecae have no
relationship with any
caecal appendages of other
Vertebrate.
• The caecae develop from
intestinal wall, they should
be designated as intestinal
caeca instead of pyloric.

32. Rectum
Morphologically there is no
distinction between the intestine.
Anus
It is the posterior opening of alimentary
canal. The region of the anus facing the
exterior has the exterior has the epithelium
continuous with the skin

33. Histology of Gut

34. Histology of Gut
• The gut is made up of usual four layers-
1. Serosa 2. Muscularis externa
3. Submucosa 4. Mucosa

35. The stomach possesses board mucosal folds
subdivided into primary and secondary folds.
The mucosa contains gastric glands-

36. In the Intestine, the mucosal, folds called villi,
which have intestinal glands-

37. Innervation of Gut
• The alimentary canal of fishes is
innervated by sympathetic and
parasympathetic components of
autonomic nervous system.

38. Metabolism of
Fish

39. Metabolisms
• The term of metabolism is commonly used to refer
specifically to the breakdown of food and it’s
transformation into energy.

40. Consists of Metabolism
 Two process-
Catabolism
Anabolism

41. Importance factors of Metabolism
 Mainly metabolism itself relies on three factors-
Respiration and Nutrition to supply metabolites.
Osmoregulation
Excretion to get rid of all the poisons and other waste
products produce as side effects.

42. What makes up fish metabolism?
The factors which can influence metabolism-
• Size
• Age
• Activity
• Condition
• Environment

43. Essential and Non-essential Amino acids of
Fish’s metabolism:
Essential Amino acid
• Arginine
• Histidine
• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophane
• Valine
Non-essential Amino acid
• Alanine
• Asspergine
• Aspertic Acid
• Cystine
• Glutamic Acid
• Glutamine
• Glycine
• Proline
• Serinr
• Tyrosine

44. Gastro-intestinal
Hormone
In Fish
Digestion

45. Gastrointestinal hormone
• Gastrointestinal hormones constitute a group of hormones produced
from specialized endocrine cells of the stomach, pancreas and small
intestine,which are secreted directly into the bloodstream.
• The gastrointestinal tract (digestive tract, GI tract, GIT, gt,
or alimentary canal) is an organ system which takes in
food, digests it to extract and absorb energy and nutrients, and expels
the remaining waste as faces.
• The GIT of fish and other vertebrates are challenged with a diversity
of functional demands caused by changes and differences in inputs
and environmental conditions.

46. Major gastrointestinal hormones are
• Secretin,
• Cholecystokinin,
• Gastrin,
• Gastric Inhibitory Peptide(GIP)
• Vesoactive Intestinal Peptide(VIP) etc.

47. Secretin
• Secreted by the lining of the duodenum (S cells) in response
to acid entering from the stomach.
• secretin acts on the pancreas to increase the output of
bicarbonate, which neutralizes the acid.
• It also increases the release of enzymes from the pancreas
and reduce gastric secretion.

48. Cholecystokinin
• Released by the duodenum (I cells) in response to fats and
acid.
• cholecystokinin causes the gallbladder to squeeze bile into
the duodenum
• It stimulates the production of pancreatic enzymes, which
pass into the duodenum through the pancreatic duct.

49. Gastrin
• Secreted mainly by cells in the stomach, Gastric antrum (G
cell) in response to eating food (especially protein)
• gastrin causes the stomach to produce more acid and
stimulates contraction of muscle in the wall of part of the
stomach, ileum, and colon.
• This contraction propels food through the digestive tract.

50. Gastric inhibitory peptide
• Secreted by the lining of the duodenum (K cells)
• Reduce gastric acid secretion and intestinal motility
• Stimulates insulin release

51. Vasoactive intestinal peptide (VIP)
• VIP is widely distributed throughout the central and
peripheral nervous systems.
• Secreted from enteric nerve
• Increase water and electrolyte secretion from pancreas and
gut.
• It simulates smooth-muscle relaxation, both in the alimentary
tract and in the systemic vasculature.
• The VIP and PP are classified as candidate hormone.

52. Others
Pancreas secrete two important hormone:
• Insulin
• Glucagon
Insulin secreted from beta cell while glucagon secreted by
alpha cell.
• Somatostatin is present in the stomach and pancreas of fishes. They are
called paracrine substances.
• It differs from hormone because it diffuses locally to the target cell
instead of releasing into blood. It inhibits the release of insulin and
glucagon from the pancreas.

53. Digestion of carbohydrate

54. Carbohydrate
• The term carbohydrates was originally derived from
a large group of Organic compounds occurring in
foods and living tissues including sugars, Starch and
cellulose. It contain hydrogen and oxygen in the
same ratio as a water (2:1) and typically can be
broken down to reduce energy in the animal body.

56. The enzymes which break down the
carbohydrates in the gut of fishes are:
1. Amylase
2. Lactase
3. Saccharsases/sucrase
4. Cellulase.

57. Process of carbohydrate Digestion
Mouth
Stomach
Pancrease and small intestine
Large intestine (Colon)
Amylase
Starch Maltose
Maltase
Glucose
Sucrose
Sucrase
Glucose+ Fructose

58. Digestion of Protein

59. Protein
• Proteins are large biomolecules, or macsomolecules,
consisting of one or more long chains of amino acid
residues.
• Protein is an important component of every cell in
the body. Proteins is an important building blocks of
bones, muscles, cartilage, skin and blood.

60. Enzymes that’s required for the digestion
of Protein
1. Pepsin (Stomach of carnivora's fishes)
2. Trypsin ( Intestine [alkaline medium], Pancreas
intestinal caecae)
3. Chymotrypsin
4. Erypsin (Collection of peptidases are known as
erypsin, found in intestine)

61. Digestion of proteins
 Protein digestion beings in fish mouth.
 The fishes which possess in stomach are generally
carnivorous & secret pepsin enzyme from gastric mucosa.
The pepsin is protease enzyme, it can break down protein.
 The stomach produce HCl, which is needed to activate
protein digestion.
 The pancrease release trypsin, another digestive enzyme,
into the small intestine. The protein molecules are reduced
in size until they can pass through the intestinal wall.
 Once the protein molecules are reduced to their smallest
component parts, they are ready to enter bloodstream.

62. Digestion of Lipid

63. Lipid
• A lipid is a biomolecule that is soluble in nonpolars solvents. Non-polar
solvents are typically hydrocarbons used to dissolbe others neutrally
occurring hydrocarbon lipid molecules that do not dissolve in water,
including fatty acids, waxes sterols, fat-soluble vitamins.

64. • For the digestion of Lipids lipases enzyme
is required.
Lipases enzyme is secreted as-
• Lingual lipases
• Pancreatic lipases
• Enteric lipases

65. Digestion of Lipid
• Pancreatic lipases is a powerful lipolytic enzyme.
• It’s digests triglycerides into monoglycerides.
• Lipase can break them into the smaller parts that can
enter the intestinal vili for digestion.
• However, lipid digestibility varies between species &
developmental stage, feeding rate, water temperature
lipid source & its melting point.

66. Absorption of
Fish

67. Absorption
• Absorption is the process by which one thing absorbs
or is absorbed by another.
• Absorption efficiencies are about 97% for the protein
fraction, and 91% for the total food consumed; they do
not vary appreciably among the individuals of different
body weights.

68. How Nutrients can enter absorptive cells?
• Nutrients can enter (or exit) absorptive cells following a
concentration gradient by simple diffusion or via the
paracellular route.
• Absorption of nutrients as studied in vitro generally appears
to occur at a faster rate in tissues from the proximal intestinal
regions compared to more distal regions in most but not all
fish species studied for example, sturgeon.

71. Types of Absorption:
Protein/Peptide/Amino Acid Absorption
Lipid Absorption
Carbohydrate Absorption
Pigment Absorption
Synthesis and Absorption of Vitamins
Minerals Absorption
 Phosphorus Absorption
 Calcium Absorption
 Magnesium Absorption
 Iodide Absorption
 Iron Absorption

72. Protein/Peptide/Amino Acid Absorption
• The carnivorous European eel is the
teleostean species in which nutrient
transport processes have been most
systematically studied.
• As indicated investigators suggest
the presence of at least four distinct
𝑁𝑎+ - dependent amino acid
transport systems in the eel: an
acidic, a basic and a neutral amino
acid transport system, analogous to
the mammalian systems

73. Lipid Absorption
• The absorption of the various lipid classes in fish is not well
understood but is presumed to occur as in mammals. Fatty acids
released from the micelles are thought to be absorbed by diffusion or
facilitated transport.

74. Carbohydrate Absorption
• In various fish species investigated, the monosaccharides D-
glucose and D-galactose appear to be transported by the same
transporter across the brush border membrane, SGLT1, and in
a similar manner as in mammals

75. Minerals Absorption
• Minerals are important components of structural and physiological
processes. Elements such as calcium, phosphorus and magnesium are
required at high levels for bone and scale formation and also have
critical roles in intracellular processes such as cell signaling and energy
metabolism.