 Excretory system  Fuction of excretory system  Excretory organ  1>Malpighian tubules  2>Nephrocyte  3>Oenocytes  5>Integument  6>rectum  →Urine production  Formation of primary urine  Movement of solute  Excreation of ions  Modification of primary urine  Salt and water balance  terrestial insects  Fresh water insect  Salt water insect  Nitrogen Excretion

1. Excretory system
Salt and water
regulation in insects

2. SYNOPSIS
 Excretory system
 Fuction of excretory
system
 Excretory organ
 1>Malpighian
tubules
 2>Nephrocyte
 3>Oenocytes
 5>Integument
 6>rectum
 →Urine production
 Formation of primary
urine
 Movement of solute
 Excreation of ions
 Modification of primary
urine
 Salt and water
balance
 terrestial insects
 Fresh water insect
 Salt water insect
 Nitrogen Excretion

3. Excretory system
 Metabolic wastes of the chemical reaction in the
cell are remove from the body.
 This process is called excretion.

4. Fuction of excretory
system
 Filtration and excretion of metabloic wastes.
 The regulation of blood content.
 Regulation of blood PH.
 Homeostasis (maintain a constant internal
envirment).

5. Excretory organ
 Different type of excretory organ
1>Malpighian tubules
 The melpighian tubules system is type of
excretory and osmoregulatory system found in
same insect , myriapods , arachnids and
tardigrads.
 The system consists of branching tubules
extending from the alimentary canal that absorbs
solutes , water and wastes from the surrounding
hemolymph.

6.  Malpighian tube lie in the haemocoel and are
attached to the gut at the junction between the
midgut and hindgut.

7. 2>Nephrocytes
 Nephrocytes a specialized cell, especially in
arthropods, whose function involves the
accumulation or formation of waste or excretory
products.
 Nephrocytes also take part in protein metabolism
and regulation of heartbeat.

8. 3>Oenocytes
 These large cell have been recorded from most
order of insect.
 They arise from the ectoderm, usually near the
abdominal spiracles and sometime remain closely
associated with the bases of the epidermal cell.
 They responsible for lipid processing and
detoxification , protect the organism against toxic
and potentially lethal compound such as
insecticides

9. 5>Integument
 The outer covering of the living tissue of an
insect.
 The body wall of many animals serves as an
excretory organ in the elimination of waste
substance from the body.
6>rectum
 Certain aquatic insect ammonia is secretes
directky into the rectum .

10. →Urine production
 A fluid must be produced in the melphigian
tubules to carry excreted substance to the
hindgut this fluid is called the primary urine
 The primary urine to differentiate it from the
modified excreta that leaves the insect in the
anus having been modification on its passage
through the hindgut.

11. Formation of primary urine
 In all insect, the movements of water into the
malpighian tubules from the haemolymph depend on
the active transfer of cation into the lumen of the
tubules.
 Potassium is usually the predominant cation , but in
insect feeding on vertebrate blood which is high in
sodium , sodium has a major role.
 The H⁺ ATPase on the apical plasma membrane ,
activated by the mitochondria in the microvilli , pump
H⁺ ions into the lumen of tubule.
 H is then exchange for potassium and sodium from
the cell, probably by a CPA2 class of exchanger.

14. Movement of solute
 Once the fluid is produce within the
tubule ,solute in the hemolymph also
move in .
 Passive diffusion is believed to occur
both between the cell (the paracellular
route-low permeability ) and through the
cell ( the transcellular route-high
permeability).
 Movement between the cell is slow for
two reason: the cell are held together by
septet junction which greatly reduce the
permeability and the area of the cleft
between cell in only a small fraction of
the total outer surface of the tubules,
especially since the infolded , increase
the surface area of the cell.
 Slow passive movement of molecules
through the intercellular gapes is also
important because it ensures that any

15. Excreation of ions
 Inorganic ion other than potassium and sodium
commonly diffuse into the urine trancellularly.
 Movement of most anion = 1
hydrated size
 Chloride generally follow the active transport of
Na or K in order to balance the postive charge on
these ion.
 Both the paracellular and transcellular has been
suggested.
 Different species may make different use of the
two pathways.

16. Modification of primary urine
 Salt and water balance
 Salt and water balance involves more than simply the
control of hemolymph osmotic pressure.
 The relative proportion of the ions that contribute to
this pressure must be maintained within narrow limits.
 Regulation of salt and water content is obviously
related to the nature of the obviously related to the
nature of the external envirment
 Different osmotic problems are faced by insect in
different habitats
 The production of a primary excretory fluid in the
malphighian tubules followed by differential resoption
from or secretion into the fluid when it reaches the
rectum.

17. Terrestial insects
The terrestial insect can regulate their hemolymph
osmotic pressure over a wide range of conditions.
In terrestial insect water is lost
1. by evaporation across the integument ,
although this is considerably reduced by the
presence of the wax layer in the epicutical .
2. During respiration through the spiracle ( many
insect posses devices both physiological and
structure for reducing the loss)
3. During excretion

20.  The major source of water for mat terrestial insects is
obviously food and drink.
 When sufficient water cannot obtain by drinking or in
food , the insect must obtain it by other means.
 One source is the water produced during
metabolism.
 Absorption of water vapor from the atmosphere is a
method employed by a few insect (example-
Thermobia and Tenebrio)which are normally found in
dry condition.
 The tubule are important in regulations since the rate
at which ion and water are excuted from the body is
the difference between their rate of secretion into the
tubule lumen and their rate of resorption by the
rectum.

21.  The rectum is the main site of water resorption in
many terrstial insect.
 Water is reabsorbed against a concentration gradient
, i.e. , it is an active process and energy is expanded.
 The rate of water movement across the rectal wall is
independent of the rate of salt accumulation.
 The rate at which water is reabsorbed depend in thee
osmotic gradient increases during resorption. The
point is reached at which the rate of active
accumulation is balanced by the rate of passive
diffusion back into the rectal lumen. The concentration
of the rectal fluid reaches a maximum value.

22. Salt balance in terrestial insect
 The production of primary urine depends on the
active movement of potassium(k+) and
sodium(Na+) into the malpighian tubules followed
by a passive moment of anions , primarily
chloride , to restore electrical equilibrium.
 The insect cannot normally sustain such a high
loss of ions from the hemolymph and they are
recoverd by reabsorbtion from the fluid.
 In the ileum and rectum the active reabsorbtion of
chloride and sodium.
 Potassium follows along the electric potential
gradient generated by the movement of chloride.

24.  Melpighian tubules –
Active trasport – K⁺ and Na ⁺
Passive trasport – Cl⁻
 Ilum and rectum –
Active trasport – Cl ⁻ and Na⁺
Passive trasport - K⁺
 In carausius(phasmatoda) 95% sodium and 80% potassium in
reabsorbed.
 The cuticle tuning of rectum limits the size of molecules which
can be absorbed as in the locust for example- it is imperrble to
molecules with a radius greater than 0.6nm.
 Glucose passes reapidly through it , but trehalose does so
onlyat a few rate and longer molecules are unable to do so .
The effect of this is to protect the rectal cells from tosic
molecules whose concentration may increase in the rectum to

25. Fresh water insect
 The regulation problems facing fresh water insect
are the opposite of those in insect from saline
condition.
 Fresh water insect tend to lose salts to the
envirment because most species have a highly
permeable cuticle.
 K⁺ ,Na⁺, Cl⁻ are reabsorbed in the rectum but
water is not.
 The production of urine which is hypoosmotic to
the hemolymph

27. .
 Beyond this point regulation break down because
fresh water insect are not able to produce a
hyperosmotic urine that is they cannot reabsorb
water against a concentration gradient.
 In freshwater insect food is the used sources of
ions which are absorbed through midgut wall.
 Ex. Papillae of mosquito that N⁺ , K⁺ , phosphate
ions are also actively transport into the papillae.

28. Salt water insect
 A number of aquatic insect live in habitats in which the
salinity varies widely.
 Ex. Aedas detritus , occur in salt marshes and the fly
coelepa frigida breeds in seaweeds washed up an the
sea shore.
 In both situation the salinity varies according to the
degree of inundation and desiccation
 Most of these insect regulate the ionic composition of
their hemolymph so that its osmotic pressure change
very little over wide range of envirmental salinity.Eg
aedes detritus and ephydra.
 Ex. Caddis fly – regulate relatively poorly but can
tolerate a three-fold increase in hemolymph osmotic
pressure.

30.  Insect living in salt water gain water and salt with
their diet and lose water osmotically.
 Saltwater insect get rid of excess ions by excreting
urine which is hypertonic to the hemolymph.
 In salt water mosquito some reabsorption occur in
anterior rectum but Na⁺, K⁺,Mg⁺⁺ and Cl⁻ ions are
secreted into the posterior rectum to create a
hypertonic fluid.
 If the insect is in a hypertonic medium ,the posterior
rectum is inactive and the insect produce hypotonic
urine.
 In this way the hemolymph osmotic pressure is
regulate.

31. Nitrogen Excretion
 Terrestrial insect excrete waste products as uric
acid or certain of its salts called urates which
were water insoluble and requires less amount of
water for waste product removal this type of
excretion is known as ‘URICOTELISM’
 In aquatic insects ammonia is the excretory
products which is poly soluble in water and
requires more amount of water for waste product
removal.
 This type of excretion is known as
‘AMMONOTELISM’