2. Introduction of Nematodes
The nematodes or roundworms constitute
the phylum Nematoda (also called
Nemathelminths) with plant-parasitic
nematodes being known as eelworms.
They are a diverse animal phylum
inhabiting a broad range of environments.
It is estimated that there may be over 1
million species of nematode.
3. • Free-living or parasitic
• Most very small < 2mm, some 1m
long
• Abundant (100 in a cupful of soil)
>20,000 named species, many others
undescribed
• Radial symmetry - cylindrical body
• Pseudocoelomate - false body cavity
• Tough cuticle must be shed to grow
• Has cephalization
4. Size :
Human and Animal parasites are big and
visible to the naked eyes
• Ascaris lumbricoides …………………...30 cm
• Dracunculus medinensis……………….1m
• Placentonema gigantissimma ………...8 m
(longest)
• Free-living nematodes microscopic
• Greeffiella minutum…………………….82 µm
(smallest)
5. Prescence in environment:
Nematodes have successfully adapted to nearly every
ecosystem:
• from marine (salt) to fresh water,
• soils, from the polar regions to the tropics,
• as well as the highest to the lowest of elevations (including
mountains).
They are ubiquitous in
• freshwater,
• marine, and
• terrestrial environments,
• are found in locations as diverse as
• mountains,
• deserts,
• and oceanic trenches
• They live in host animals and plants as parasites.
7. Osmoregulation and Excretion:
Excretory glands and canals
thought to be involved in:
• Osmoregulation
• Ionic regulation
• Excretion of waste metabolites
• Ammonia secreted through
body wall.
8. Introduction
• Excretory system is one of the most simplest system of
nematodes.
• Waste is turned into ammonia and is excreted through the
body.
• The major nitrogenous waste product is ammonia.
• The excretory products of nematodes are numerous like
amino acid , peptides, uric acid , fatty acid
• The excretory pore is located in the anterior mid ventral line
close to the nerve ring.
• Parasitic worms tend to have a glandular process to
excrete.
• Nonparasitic worms tend to have a much more tubular
method of releasing their salty waste.
9. Components of Excretory System
Four different cell types:
• A pair of gland cell
• One canal cell (Excretory
cell)
• One duct cell
• One pore cell
10. Phylum Nematoda divided into two
classes based on the type of excretory
system:
1.Glandular Type :
•Present in class Adenophorea
2.Tubular Type
•Present in class Secernentea
11. Canalicular or Tubular type
• Present in Class Secernentea Basically H–
shaped,
• variable Two main longitudinal excretory
ducts running in lateral hypodermal
chords Joined in esophageal region by a
transverse duct
• A terminal duct arises and opens on
ventral side the excretory pore
12. Glandular type
Present in Class Adenophorea
Single (Renette) cell leads
to an excretory duct and
opens outside through pore
13. Nitrogenous waste is excreted in the form of
ammonia through the body wall, and is not
associated with any specific organs. However,
the structures for excreting salt to maintain
osmoregulation are typically more complex.
Renette cell: The renette cell is a glandular
type of secretory-excretory organ. It consists of
a single gland cell situated near the base of the
esophagus. From the cell there extends
anteriorly a renette duct, which usually swells
into an ampulla close to the ventral pore.
14. Structure of Renette Cells:
In many marine nematodes, one or two
unicellular 'renette glands' excrete salt through a
pore on the underside of the animal, close to the
pharynx. In most other nematodes, these
specialized cells have been replaced by an organ
consisting of two parallel ducts connected by a
single transverse duct. This transverse duct
opens into a common canal that runs to the
excretory pore.
15.
16. Function of Renette Cells:
Specialized cells for excretion, which are
known as renette cells and are unique to the
phylum, remove nitrogen-laden wastes.
They have the potential to be important to
processes occurring in
• lakes,
• streams, and
• other freshwater habitats.
The waste leaves the body.
17. Caudal Glands:
Both the renette cell and caudal glands
are common in adenophorean
nematodes.
Aquatic nematodes with renette and
caudal glands share the property of
secreting an adhesive material that
allows for anchorage in a current of
water; currently, this secretory function is
attributed only to the caudal glands.
18. Alternate Cellular Means of Excretion
There are certain cells in the nematode body
which help in excretion:
• Hypodermal glands: They enhances the
efficiency of excretion by functioning
throughout the length of the body.
• Prerectum: It is the connection between
intestine and rectum.
• Coelomocytes : These are the cells situated
in the body cavity.
19. Significance of Excretory System
Maintaining osmoregulation.
• Regulating turgor pressure in the body cavity.
• Removes foreign particle.
• In female of citrus nematode Tylenchulus
semipenetrans, excretory pore is located
posteriorly and it is responsible for the secretion
of the gelatinous matrix surrounding the eggs.
• Ecdysis is accompanied by the synthesis of the
enzyme leucine aminopeptidase in the excretory
gland and its release via the excretory duct into
the space between the two cuticles in
Phocanema
20. Conclusion:
In nematodes, specialized excretory systems are
not well developed.
Nitrogenous wastes may be lost by diffusion
through the entire body or into the
pseudocoelom (body cavity), where they are
removed by specialized cells.
Regulation of water and salt content of the
body is achieved by renette glands, present
under the pharynx in marine nematodes.
