fish endocrinology

1. INSECT AND CRUSTACEAN
ENDOCIRINOLOGY
By
Dr .A.Krishnamoorthi
Assistant Professor in zoology ,
Arignar Anna Government Arts College ,Namakkal

2. 1 Introduction
 Neurosecretions are the main sources of hormone in the
invertebrates.
 Neurosecretion is the storage, synthesis and release
of hormones from neurons.
 These neurohormones, produced by neurosecretory cells,
are normally secreted from nerve cells in the brain that
then circulate into the blood.
 These neurohormones are similar to non-
neural endocrine cells and glands in that they also
regulate both endocrine and non-endocrine cells.

3.  Neurosecretion cells synthesize and package their
product in vesicles and exocytose them at axon
endings just as normal neurons do, but release their
product fartheir from their target than normal neurons
(which release their neurotransmitters short distances
at synapses), typically releasing their neurohormones
into the circulatory system to reach their distant targets.
 In invertebrate neurosecretions appear to regulate
growth, regeneration, metamorphosis and reproductive
activities.

4. Neuroendocrine system in Crustacea
 A typical crustacean, the neuro-endocrine system has
the following components.
 1. Neurosecretory cells: In crustaceans, neurosecretory
cells are located in the brain, portions of the optic
lobe and all the ganglia of the ventral nerve cord.
 2.The neurosecretory X-organ or organ of Bellonci and
its associated three neurohemal organ:
i)The sinus gland. Both an X-organ and a sinus
gland are located in each eyestalk, and together they
are termed the eyestalk complex.

5. They made up of axon termini from the neurosecretory
cells of brain and optic ganglia. They receive storage
and release hormones secreted from neurosecretory cells
in brain and the optic lobe. Sinus gland contains
chromatophorotropin hormone and moult-inhibiting
hormone.
(ii)The post commisure organ located immediately
posterior to the oesophagus and receiving axon from
the brain. It serves as a centre for storage and
release of secretion from the posterior part of the
brain(tritocerebraum). It affects the colour changes
(chromatophorotropin hormone).

6. (iii)The pericardial organ located in the wall of the
pericardium. They consist of neurosecretory cells and
axon terminals from various ventral ganglia. The
secretions of the organs are concentrated with the
increased heart beat and also responsible for the
regulation of gas transport and exchange.

7. 3. There are three non-neural endocrine glands
namely:
 (i) The Y-organ located within antennary or
maxillary segments. It secretes a hormone that
influences moulting. It secretion is regulated by the X-
organ complex. An eye stalk hormone appears to
inhibit production of Y-organ hormone.
 (ii) Androgenic gland found in male crustaceans. Its
secretion is responsible for development of male
secondary sexual characters. The gland located on the
wall of the vasdeferens. It is performed by interstitial
cells of the testes.
 (iii) Ovaries found in female. Its secretion is
responsible for female secondary sexual characters.

8. Role of neuroendocrine system
 The various physiological process regulated by the
neuroendocrine system is divided into three groups
namely, kinetic, morphological and metabolic process.
 The kinetic process includes somatic pigmentation,
retinal pigment migration and cardiac regulation.

9. Colour changes or somatic pigmentation
 The neurohormones known as chromatophorotropins
secreted by the pigment cells (chromatophores) have
been found in the eyestalk complex and almost all part
of the nervous system that regulate colour changes.
 The best known are the light-adapting hormone and
the red-pigment-concentrating hormone.
 Regulation of the chromatophores allows an animal to
adapt to different backgrounds by changing colours or
by becoming lighter or darker.

10. Control of retinal pigment
movements
 Crustacean eye is a compound structure compost of
many units called ommatidia.
 The ommatidium consists of three sets of pigments
namely, proximal retinal pigment, distal retinal pigments
and reflecting pigment.
 The movement of pigments are under the control of
the hormone of the eye-stalk and brain.

11. Cardiac regulation
 In most crustaceans, the heart is neurogenic with
elongated dorsal cardiac ganglion acting as the
pacemaker.
 Heart rate is accelerated in crustaceans by a factor
called Myotropic factor released from the pericardial
organs.
 Extracts of these organs found to contain 5–hydroxyl-
tryptamine which increased heart rate and also regulates
gas transport and exchange.

12. Moulting
 Growth is discontinuous process in arthropods.
 Increase in size being restricted to the period between
loss of the old exoskeleton and expansion and
hardening of the new one.
 Moulting may be a seasonal or continuous process and
it is influenced by a great variety of environmental
factors.
 Externally moulting may be appear sloughing off of the
hard exoskeleton to allow internal growth, internally it is
a complex metabolic adjustments and a well coordinated
neuro-endocrine mechanism operates this complex
process.
 In crustaceans, molt cycle occurs in four stages.
 Pre-moult, moult, post-moult and inter-moult.

13. Premoult (proecdysis)
 Pre-moult (proecdysis) stage occurs just prior to
exuviation, and is characterized by separation of the
old exoskeleton from the underlying epidermal layer.
 The old exoskeleton is partly reabsorbed, and energy
reserves are mobilized from the midgut gland.
 Pre-moult begins with an increase in concentration of
moulting hormone in the hemolymph.
 The first indication that the prawn is entering proecdysis
is the withdrawal of the epidermis from the old cuticle
(apolysis).

14.  Later the epidermis starts to hypertrophy and cells,
which appear to have a storage function, accumulate
in it.
 As the prawn proceeds through this stage, the
epidermis starts to secrete a new epicuticle and
exocuticle.
 Feeding starts to decline and has completely ceased
by the end of the proecdysis.
 Oxygen consumption increases, glycogen is deposited
in the hypodemic tissue of the old cuticle and lost
limbs are regenerated rapidly.
 The materials for cuticle synthesis are derived from
two sources: accumulated reserves due to feeding and
resorption from the old cuticle.

16. Moult or Ecdysis
 Ecdysis, as a stage, only lasts a few minutes.
 It begins with the old exoskeleton opening at
the dorsal junction of the thorax and abdomen
in decapod crustaceans, and is completed when
the animal escapes from its confines.
 Moult is sloughing off of the old cuticle.
 This is accompanied by a marked increase in
size which accounts for rapid absorption of
water immediately after removal of the old
cuticle and the cuticle hardens appreciably
within a few hours afterwards.

17.  The steroid hormone ecdysone secreted from the Y-
organ stimulates moulting.
 After it is released into the blood, ecdysone is
converted to a 20-hydroxyecdysone, which is the
active moulting hormone.
 Edysone is blocked by a neurohormone called moult-
inhibiting hormone, produced by the eyestalk complex.
 In moult of the crustacean, the ablation of eyestalk
bring about accelerate the moulting cycle.

19. Post-moult (postecdysis)
 Post-moult is the stage just following exuviation
(shedding of the old exoskeleton).
 It is the period when the exoskeleton expands due to
increased hemolymph volume from water influx.
 Water influx occurs across the epidermis, gills, and gut.
 After several hours or days (depending upon total
length of the molt cycle), the new exoskeleton hardens
and retains its rigidity.
 Immediately after ecdysis, the only layers present are
the epicuticle and exocuticle.
 Within a few hours the epidermis starts to secrete the
endocuticle.

20.  Most of the cuticle must be derived from materials
stored in the epidermis, as feeding does not begin until
the prawn is well into the inter-moult stage.
 This secretion continues until the prawns are in the
inter-moult condition, when the three layers are fully
formed

21. Inter-moult
 During inter-moult the exoskeleton becomes much
harder through mineral and protein deposition.
 Shrimp exoskeleton is relatively thin and soft compared
to crabs and lobsters (Chang, 1992).
 The volume, as well as the weight of the whole prawn
increases by 3-4% during the intermoult period.
 This increase may be due to extension of the thin
intersegmental connections of the abdomen, and
supports the concept that growth in penaeids is a more
continuous process than in the heavily armoured
decapods, which moult relatively infrequently.

22.  The X-organ sinus gland complex and Y-organ regulate
the process of moulting.
 The Y-organ performs a positive role in this process.
 Internal and external environmental conditions influence
the moulting pattern by either affecting the production of
MIH in the X organ or it release from the sinus gland.
 The function of Y organ is under the control of
circulating titters of MIH.
 During moulting phase concentration of MH higher and
the moulting is switched on.
 On other hand, when concentration of MIH increases it
inhibit Y-organ to synthesis MH and inhibition of
moulting process.
 The time and duration of each period may be varies
according to geographical distribution, environmental
condition age and sex of the animals.

24. Reproduction
 Most of the crustaceans are bisexual with clear cut
sexual dimorphism.
 sex is determined genetically, but the morphological and
functional expression are under the control of hormone.
 At the younger stages the sexes cannot be
distinguished however, the sexual differentiation
progressed with successive moults and continuous up to
the gonadal maturity and complete development of
secondary sexual characters.

25. Male reproductive hormone:
 The male sex hormone is produced by a pair of
androgenic glands located end of the each vasdeferens.
 In a genetic female, they fail to develop. But in male
the gland enlarged to form solid strand of cells, folded
several times and become functional androgenic glands.
 It is a holocrine gland, that is secretes total content
into the blood.
 The peptide hormone secreted by the androgenic glands
influence the normal development of testes and
subsequent spermatogenesis and expression of secondary
sexual characteristics

26.  In addition to this, injection of extract from the sub-
oesophageal and thoracic ganglia accelerate the gonadal
development.
 This indicates that, some gonads accelerating factor
present in these ganglia.
 It is experimentally proved that, in shrimps and other
crustaceans the removal of androgenic glands or their
testes tent to function like ovaries.
 They spontaneously develop oocytes from primary germ
cells instead of sperms.
 When the androgenic glands are removed such
operation leads to either partial or complete castration of
a male individual.
 From this concluded that, the normal functional state of
testes and maintenance of secondary sexual character is
controlled by the male sex hormone secreted by the
androgenic glands.
 Testes as an organ however, have no endocrine role.

27. Female reproductive hormone:
 The normal functional state of the ovary and female
secondary sexual characters are controlled by two
hormones released from X organ sinus gland complex
of the eye stalk and the ovary.
 The eyestalk complex appears to produce a
neurohormone called ovary inhibiting hormone
that inhibits enlargement of ovary and vitellogenesis by
the fat body and blocks vitellogenin (yolk) deposition
in the oocytes in the ovary.
 Older follicles in the ovary, however, may secrete a
vitellogenin-stimulating hormone that overrides the effects
of the eyestalk neurohormone.

28.  During moulting, the ovarian inhibition hormone is
produced in large quantities thereby inhibiting
reproductive phase.
 On the other hand, during reproductive phase moult
inhibiting hormone is secretes in large quantities this
preventing the process of moulting.

29. Osmoregulation
 There are four known sources of factors that influence
water and ionic balance (osmoregulation) in
crustaceans.
 The brain factor is known to regulate function of the
antennal glands (paired “kidneys” located at the base
of each antenna), the intestine, and the gills.
 The thoracic ganglion factor affects the stomach,
intestine, and gills.
 Both the antennal glands and the gills are affected by a
factor from the eyestalk complex.
 Finally, the pericardial organs (neurohemal glands
located in the pericardial cavity) influence salt and water
metabolism by heart muscle and gills.

30. Neuroendocrine system in Insects
 In insect, various life process like growth, metabolism,
colour adaptation and reproduction are controlled by well
coordinated endocrine system.
 The neuro-endocrine system of a typical insect is
compost of both aggregation of neurosecretory nuclei in
different regions of the nervous system and specialized
non neural endocrine glans.
 Insects contains two neurosecretory nuclei namely,
cerebral ganglia and corpora cardiaca, the non-neural
organs namely, corpora allata and prothoracic gland or
ecdysial gland.

31.  Cerebral ganglions are the important neurosecretory
centre of insects.
 It has two median ganglions and two lateral ganglions.
 Axons from the median ganglions cross each other and
emerging from the brain forming a pair of nerves called
Nervi Corporis Cardiaci-I (NCC-I) extend to a
neurohaemal organ corpora cardiac.
 The lateral ganglia or B-cells are usually smaller in size
and fewer in numbers then the median cells or ganglia.
 From these a paired nerves directly emerged out and
joint with corpora cardiaca that is called nervicorporis II
(NCC-II).
Cerebral ganglia

32.  They located lateral to the NCC-I. In some cases the
third group of trito-cerebral nuclei are present.
 From this the axons directly enter to the corpora
cardiac via NCC-III.
 These are the cerebral ganglions or cells found in the
various groups of insects.
 In addition to this, neurosecretory cells also found in
sub-oesophageal and other ganglia of ventral nerve
cords.
 The presence of neurosecretory cells in the sub-
oesophageal ganglia is a characteristic feature of
throughout the insect order.

34. Corpora cardiaca
 Corpora cardiaca are the principal neurohaemal organs
located just below the brain.
 They are small paired structure, bluish in appearance.
 The nerve trunks from cerebral ganglia (NCC-I, II and
III) are end in the corpora cardiaca. Each corpora
cardiaca is again connected to its corresponding corpora
allatum by a single nerve nervous corpora allati.
 Corpora allati composed of axons originating from the
brain.
 The corpora cardiaca can be considered as a modified
nerve ganglia functioning as a neurohaemal organ.
 Moreover, some nerve cells located in it may function
as neurosecretory cells.

35.  A large portion of the cardiacum is composed of axons
terminals of the brain neurosecretory cells.
 The neurosecretion of the cerebral nuclei may be
stored here or released directly into the haemolymph.
 But the secretory cells have been identified in cardiaca
from many species that function is not yet understood.

36. Corpoa allata
 The corpora allata are a non neural endocrine gland
located immediately below the corpora cardiaca.
 It is an ectodermal in origin, appeared as a solid
structure and ovoid in shape.
 The allata receive a pair of nerves from corpora
cardiaca which are primarily the extensions of the nervi
corporis cardiaci-I.
 Thus the allata becomes the segment of the
protocephalic neurosecretory pathway that extends from
the protocerebrum through the corpora cardiaca into the
allata.
 The corpora allata is the sources of juvenile hormone
(JH) or neotensis which play an important role in the
life cycle of insect particularly in the process of
moulting.

37. Prothoracic gland or Ecdysial gland
 Prothoracic gland is a second non neural endocrine
gland arising from the ectodermal cells.
 The gland usually in pair and their location is varies in
different group of insects.
 Mainly it found in prothorax hence, it is called
prothoracic gland.
 It plays an important role in the process of moult or
ecdysis.
 The functioning of the scdysial gland is controlled by a
tropic hormone released from the corpora cardiacum.
 The ecdysial gland secretes a steroid hormone called
ecdysone.
 It plays an important role in the process of growth and
development.

38. Endocrine control of moulting and
metamorphosis
 The endocrine systems in insects control growth and
development.
 In insects growth is a discontinuous process that leads
towards maturity through stages or instars.
 A key feature of insects is that they have exoskeletons.
 For an insect to grow, at the end of each instar
moulting occurs.
 During moulting the old binding exoskeleton is shed with
the formation of new one to providing space for further
growth of body.
 This shedding process is called moulting or ecdysis.

39.  The life of an insect consists of a series of discrete steps:
 growing followed by moulting, then more growing followed by
moulting, and so on.
 However, the rigid exoskeleton cannot change shape between
moults.
 In the moult cycle, final moult is the very important changes
because it is the period during which the adult characters
are formed with the concurrent loss of specific juvenile
structure. This means that all the changes of external
shape in the life of an insect must occur during
moulting.
 This transformation from an immature juvenile to a
mature adult is termed as metamorphosis.
 In this way, the moulting process is intimately
connected to both growth and morphological
development.

40.  The process of growth and development is controlled by
three endocrine sources namely, the brain, ecdysal
gland and corpora allata.
 There are three hormones regulates growth and
development they are first one is prothoracicotropic
hormone (PTTH), a peptide tropic hormone secreted by
brain neurosecretory cells.
 The second is ecdysone, a steroid secreted by non-
neural endocrine cells in the pro-thoracic glands.
 PTTH controls secretion of ecdysone. Juvenile hormone
(JH) is the third hormone of primary importance in the
control of moulting.
 It is secreted into the general circulation by non
neural endocrine cells in the corpora allata

41.  Neurosecretory cells in the brain secretes
prothoracicotropic hormone or ecdysiotropin hormone
which is stored in the corpora cardiaca.
 The brain has a computational power to determine
when each moult will occur.
 The neurosecretory cells that secrete PTTH is receive
synaptic inputs from other, ordinary brain neurons that
control when the neurosecretory cells will secrete their
hormone.
 On stimulation from the ventral nerve cord to the brain
via the axons of the brain the corpora cardiaca release
the PTTH to blood (haemolymph).

42.  During each episode of PTTH secretion, the flow of
blood carries the PTTH to the two pro-thoracic glands,
where it stimulates to secrete ecdysone hormone.
 As the ecdysone circulates, it undergoes peripheral
activation to form 20-hydroxyecdysone, a hormone that
primarily affects the insect’s epidermis, the layer of
living tissue just inside the exoskeleton.
 The epidermis secretes the exoskeleton. The hormone,
being a steroid, enters the epidermal cells.
 There it combines with intracellular receptors, which
alter gene transcription patterns.

43.  As a result, the epidermal cells secrete enzymes that
loosen their connection with the old exoskeleton,
allowing the old exoskeleton to be shed.
 Then the epidermal cells synthesize a new, larger
exoskeleton and differentiation of tissue.
 In other words, a moult occurs.

45.  At that time, Juvenile hormone (JH) is secreted into the
general circulation by non-neural endocrine cells in the
corpora allata .
 It is lipid-soluble and enters target cells to starts life
as a larva (caterpillar), retains its larval form for
several moults, and then metamorphoses into an adult.
 It is observed that, each cell of the body has
multiple sets of genes which transfer the body into
immature or mature characters.
 Some insects, such as moths and butterflies, undergo
a complete metamorphosis during their development.
 In this respect JH play an important role in retaining
juvenile characters after each moult.

46.  When a larva moults, it retains its larval form if JH is
at high concentration in the blood during the moulting
process.
 During the early life of an individual, the blood
concentration of JH is high.
 Moulting thus results in a series of larger and larger
larval forms .
 Later in life, however, JH secretion is reduced, and
the JH concentration in the blood falls to a low level.
 At that point, when moulting occurs, the juvenile form
is not retained.
 Instead, the insect enters a resting stage of distinctive
body form, called a pupa.
 During the inactive pupal stage, the insect’s

47. During the inactive pupal stage, the insect’s body is
extensively remodelled inside the pupal exoskeleton.
Then, when the insect moults yet again without a high
concentration of JH in the blood, the individual emerges
as an adult.

48. Hormonal regulation of
Reproduction
 The initiation and termination of some reproductive
events often depend on environmental factors, such
as temperature, humidity, photoperiod, or availability
of food or a suitable egg-laying site.
 Additionally, these external influences may be modified
by internal factors such as nutritional condition and the
state of maturation of the oocytes.
 Copulation also may trigger oocyte development,
oviposition, and inhibition of sexual receptivity in the
female via enzymes or peptides transferred to the
female reproductive tract in male accessory gland
secretions.

49.  Regulation of reproduction is complex and involves
sensory receptors, neuronal transmission, and integration
of messages in the brain, as well as chemical
messengers (hormones) transported in the hemolymph
or via the nerve axons to target tissues or to other
endocrine glands.
 Certain parts of the nervous system, particularly
neuro-secretory cells in the brain, produce
neurohormones or neuropeptides (proteinaceous
messengers) and also control the synthesis of two
groups of insect hormones — the ecdysteroids and the
juvenile hormones (JH).
 Neuropeptides, steroid hormones, and JH all play
essential roles in the regulation of reproduction,

50.  Juvenile hormones and/or ecdysteroids are essential
to reproduction, with JH mostly triggering the functioning
of organs such as the ovary, accessory glands, and fat
body, whereas ecdysteroids influence morphogenesis
as well as gonad functions.
 Neuropeptides play various roles at different stages
of reproduction, as they regulate endocrine function
(via the corpora allata and prothoracic glands) and
also directly influence reproductive events, especially
ovulation and oviposition or larviposition.

51.  The role of neuropeptides in control of reproduction
is an expanding area of research, made possible
by new technologies, especially in biochemistry and
molecular biology.
 To date, most studies have concentrated on the
Diptera (especially Drosophila, mosquitoes, and
houseflies), the Lepidoptera (especially the tobacco
hornworm, Manduca sexta), locusts, and cockroaches.

52. Examples of some important insect physiological
processes mediated by neuropeptides.

53. Neuropeptide Action
Growth and development
Allatostatins and allatotropins Induce/regulate juvenile hormone (JH)
production
Bursicon Controls cuticular sclerotization
Crustacean cardioactive peptide (CCAP) Switches on ecdysis behaviour
Diapause hormone (DH) Causes dormancy in silkworm eggs
Pre-ecdysis triggering hormone (PETH) Stimulates pre-ecdysis behaviour
Ecdysis triggering hormone (ETH) Initiates events at ecdysis
Eclosion hormone (EH) Controls events at ecdysis
JH esterase inducing factor Stimulates JH degradative enzyme
Prothoracicotropic hormone (PTTH) Induces ecdysteroid secretion from
prothoracic gland
Puparium tanning factor Accelerates fly puparium tanning

54. Reproduction
Antigonadotropin (e. g. oostatic
hormone, OH)
Suppresses oocyte development
Ovarian ecdysteroidogenic
hormone (OEH = EDNH)
Stimulates ovarian ecdysteroid
production
Ovary maturing peptide (OMP) Stimulates egg development
Oviposition peptides Stimulate egg deposition
Prothoracicotropic hormone (PTTH) Affects egg development
Pheromone biosynthesis activating
neuropeptide
Regulates pheromone production
(PBAN)

55. Homeostasis
Metabolic peptides (= AKH/RPCH
family)
Adipokinetic hormone (AKH) Releases lipid from fat body
Hyperglycemic hormone Releases carbohydrate from fat body
Hypoglycemic hormone Enhances carbohydrate uptake
Protein synthesis factors Enhance fat body protein synthesis

56. Diuretic and antidiuretic peptides
Antidiuretic peptide (ADP) Suppresses water excretion
Diuretic peptide (DP) Enhances water excretion
Chloride-transport stimulating
hormone
Stimulates Cl− absorption (rectum)
Ion-transport peptide (ITP) Stimulates Cl− absorption (ileum)
Myotropic peptides
Cardiopeptides Increase heartbeat rate
Kinin family (e. g. leukokinins and
myosuppressins)
Regulate gut contraction
Proctolin Modifies excitation response of some
muscles

57. Chromatotropic peptides
Melanization and reddish coloration
hormone (MRCH)
Induces darkening
Pigment-dispersing hormone (PDH) Disperses pigment
Corazonin Darkens pigment

58.  The transition from ecdysterone production by the pre-
adult prothoracic gland to the adult ovary varies
between taxa. (After Raabe 1986)
 In summary, reproduction in different class of insects is
controlled by a well defined neuroendocrine
phenomenon, in which central nervous system plays a
key role.
 Even though various external and internal stimuli
regulates on it, set a series of neuro-endocrine
adjustments leading to the development of gonads and
switching on the secondary reproductive behavioural
adjustment.
 The experimental evidences prove that, main endocrine
sources controlling reproduction are brain, corpora allata
and pro-thoracic gland.

59. DIAPAUSES
 Diapauses, is a resting phase in the life cycle of an
insect as a result of arrested development.
 It is a condition of reduced metabolism and various
other changes like decreased body water and
responsiveness to external stimulus.
 The temporary adjustments to avoid death, otherwise
possible due to unfavourable conditions, involve a
change in the neuro-endocrine regulation.
 Diapauses may occur at any stage of the life cycle
from egg to the adult.

60.  The females emerging from eggs exposed to long
photoperiods and high environmental temperature
produces diapauses egg to avoid the environmental
stress during post embryonic development.
 A definite neroendocrine are controls the production of
these eggs.
 In Bombyx mori, it is observed that, the diapauses
hormone is synthesised and released from the nero-
secretory cells in the sub-oesophageal ganglion.
 The hormone acts upon the eggs when they are still
in the genital tract.

61.  As compared to eggs, larval or nymphal diapauses
have received little attention.
 Pupa diapauses generally terminate following the period
of reduced temperature.
 During this phase proto-cerebral neurosecretory cells of
the diapausing pupa regain their activities.
 The neruo-hormone released from the cells stimulates
the ecdysial gland to release ecdysone which terminates
the diapauses.
 Many insects are able to enter the diapauses condition
at an adult stage but very little is known about the
neuroendocrine regulation of this phenomenon.

62. Hormonal control of
osmoregulation
 Insects and other arthropods, such as crayfish and
crabs, have elaborate endocrine systems.
 For example, many insects have anti-diuretic and
diuretic hormones that control excretion of water by the
insect organs that serve kidney functions.
 Diuretic hormones promote excretion of a high volume
of water.
 Some of the blood-sucking insects secrete diuretic
hormones immediately after each blood meal.
 These hormones promote rapid excretion of much of
the water in the blood, thereby concentrating the
nutritious part of the meal (e.g., the blood proteins)
in the gut.

63. Colour adaptation
 In insects, both morphological and physiological colour
changes are occurs.
 In general, physiological colour changes are influenced
by two endocrine principal originating from sub-oesophageal
ganglion and tritocerebrum and a weaker effect substance
from corpora cardiaca.
 Generally, under the influence of them darkening of the
epidermis is brought about.
 The environmental stimulus which influence the activity of
nerosecretory cells in light.
 Morphological colour changes usually occur during ontogenetic
development and hormones must be modifying the metabolic
pathway involved in synthesis of different indegumentary
pigments.
 Generally, coloration of the environment influences the body
colour in response to ecdysial gland.

64. THANK YOU