Insect reproductive system

1. INSECTS
REPRODUCTION
And
endicrinology

2. The male and female reproductive system consists of paired
gonads connected to leads gonopore.
Accessory glands are present concerned with spermatophore
formation .
Female provides a glue for sticking the eggs to the substratum.
Female has spermatheca for storing sperms after copulation.
Insects are not sexually mature when they have completed the
final moult to adult.
An adult diapause stage there may be considerable delay before
mature sex cells are produced.

3. MALE REPRODUCTIVE SYSTEM
Male reproductive organs are
 testis
 Vas deferens
 Ejaculatory duct
 Accessory glands

4. TESTIS
Lie above or below the gut in the abdomen.
Consists of number of testis tubes and follicles.
Coleoptera Adephaga, has single follicle
Lice has two follicles
Acrididae there may be over 1000.
Cerambycid Prionoplus testis has 12 to 15 lobes with 15 follicles.
Walls of follicles has thin epithelium standing on basement membrane.
Epithelium has two layers of cells
a epithelium of follicle
Peritoneal sheath

5. VAS DEFERENS
Testis follicle , vas efferens connects with vas
deferens with thick epithelium .
Vasa deferentia run backwards lead into ejaculatory
duct and dilated from the seminal vesicles.
Acrididae , the seminal vesicles are separate
diverticula arising from the ejaculatory duct.
Diptera has a common seminal vesicle.

6. EJACULATORY DUCT
Ectodermal in origin lined by cuticle, wall is muscular.
Apis entirely without muscles.
In locusta, ejaculatory duct consists of upper and lower ducts connected
with funnel like constriction .
Lumen of lower ejaculatory duct is circular leads with spermatophore
sac .
Oncopeltus, ejaculatory duct is also extremely complex specialized for
erection of penis.
Ephemeroptera have no ejaculatory duct and vasa deferentia lead
directly to paired genital openings.
Forficula, right hand ejaculatory duct is fully functional, while the left
hand duct if vestigial .

7. ACCESSORY GLANDS
Male accessory glands open into vasa deferentia.
Ectodermal in origin when they are known as ectadenia .
In mesodermal origin when they are known as mesadenia.
In tenebrio, both ectadenia and mesadenia are present.
Number of accessory glands are varies considerably.
Locusta has 15 pairs of glands
Periplaneta has large number of glands which produces various
secretions.
The secretion of accessory glands mix with the sperm in the seminal
fluid and produces spermatophores in some insects.

9. SPERMATOGENESIS
Each testis follicle has germ cells divide to produce speramtogonia.
Homoptera and Lepidoptera , the spermatogonia obtain nutrients.
In Diptera, the transfer of mitochondria from the apical complex to
spermatogonia.
These apical connections are lost, the spermatogonia associate with
other cells which forms a cyst around them.
The cyst cells may be spermatogonia which lack adequate nutrition and
fail to continue their normal development.
There may supply nutrient to the developing sperm.

10. In general, all the cells in the cyst to form primary spermatogonium with
their subsequent development.
Number of sperm which a cyst produces depends on the number of
spermatogonial divisions occur.
In acrididae , 5 to 8 spermatogonial divisions occur.
Melanoplus, has 7 divisions before meiosis has 512 sperm per cyst.
The timetaken for the completion of spermatogenesis varies.
In melanoplus, the period is about 28 days .
In most insects, meiosis is complete and in insects which donot feed as
adults spermatogenesis may be complete before the adult emerges.

11. STRUCTURE OF MATURE SPERMATOZOA
Mature sperms of homoptera , heteroptera are filamentous in form.
Head region occupied by nucleus with thin coating of cytoplasm ,infront
of nucleus is the acrosome is present.
Centriole is present behind the nucleus and it arises the axial filament
which runs the tail of the sperm.
In drosophila, has a ring of 9 doublets, surrounding 2 central tubules.
Outside the ring microtubules are present .
These are produces the lashing of sperm tail and to produce movement.
In coccids, occur in sperm bundles are lacking in all the typical
organelles.

12. SPERMIOGENESIS
The spermatid which is formed after meiosis a rounded cell containing normal cell
organelles it modified to form the sperm.
ACROSOME
In golgi material, speramtocytes is scattered through the cytoplasm.
Consists of several pairs of parallel membranes with vesicles and vacuoles.
After the 2nd meiotic division, dictyosomes fuse to form to a single body called
acroblast.
Later it forms proacrosomal granule which appears in the cup shaped.
These granule associated with interstitial membrane moves towards the nucleus
and attached it.
The proacrosomal granule forms the acrosome becoming cone shaped and
developing a cavity in which an inner core is formed.

13. MITOCHONDRIA
In spermatid, the mitochondria fuse to form a single large body, the
nebenkern.
Consists of outer limiting membrane and central pool of mitochondrial
components.
Nebenkern divides into 2 parts associated with axial filament.
This part elongates to form a ribbon like structure .
Axial filament arises in spermatid from the centriole.
After the 2nd meiotic division a cone shaped centriole is present.
Microtubules are formed inside to extended the axis into the tail region.
Later the complete sperm will developed called acrosome.

14. FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of
 Ovary
 Oviduct
 Spermatheca
 Accessory glands

15. OVARY
Lie in the abdomen above or lateral to the gut.
Consists of egg tubes or ovarioles.
In schistocera reared 96 ovarioles in the 2 ovaries.
In diptera has about 100 ovarioles in each ovary.
In eutermes, has 2000 ovarioles in each ovary.
Ovarioles madeup of 2 layers are as
An outer ovariole sheath
An inner tunica propria.

16. An outer sheath is a cellular network of modified fatty tissue.
Rich in lipids and glycogen , metabolically active.
The tunica propria is an elastic membrane containing fine fibrils.
It surrounds the whole of the ovariole and the terminal filament.
In vitellogenesis, when the oocyte enlarges these membrane
becomes stretched and thin.
Tunica propria function of its elasticity , it plays a part in
ovulation.

17. OVIDUCT
Oviducts are tubes with walls of a single layer of cuboid or columnar cells standing
on basement membrane.
In acridoidea, 2 lateral oviducts join a median oviduct which is lined by cuticle.
In ephemeroptera , the lateral oviducts opening separately by 2 gonopores.
Sometimes the genital chamber becomes tubular connects to oviduct.
This continuation called vagina and its opening vulva.
In viviparous, Vagina is developed to form a pouch , the bursa copulatrix which
receives the penis.
In insects,Most female has 2 reproductive openings
One is serves for discharge of eggs known as oviparous
Other is the copulatory opening ,the vulva.

18. SPERMATHECA
Serves for the storage of sperms for the time the female is impregnated
until the eggs are fertilised , is present in most female insects.
In orthoptera, spermatheca opens into the genital chamber connected
to oviduct.
The spermatheca is ectodermal in origin and it is lined by cuticle .
It consist of storage pouch with muscular duct leading to , there is an
associate gland .
It produces more secretions which provides nutrients to the sperm.

19. ACCESSORY GLANDS
 Arises form the genital chamber or vagina.
 The glands produces the substances for attaching eggs to the substratum during
oviposition.
 It is called as colleterial glands.
 In insects laid in an ootheca consisting of tanned ,cuticle like substance which is
produced in the accessory glands.
 2 glands open into the genital chamber and each consist of mass of branched
tubules.
 These glands produces secretions with lined by microvilli projecting into it.
 In the distal end ,microvilli are free. But in proximal end it contains dense
network .
 It produces the protein in which the ootheca is formed.

20. In addition, the glands are produces
 ß-glucoside
 Protocatechuric acid
 Oxidase
These glands mix in genital chamber to produces definite structure to
the cells.
These glands which forms eggpod .
It produces silk which forms the cocoon .
Cocoon is moulded to the shape of abdomen and the eggs are laid.
Finally it sealed off and remains floating on the surface of water in some
insects.
It equipped with silken “mast” which serves as respiratory function.

22. OOGENESIS
 Each ovariole consists of a distal germarium in which the oocytes are produced
from oogonia.
 The germarium contains prefollicular tissues and stemline oogonia.
 The stem line oogonia becomes a definite oogonium and develops into an
oocyte.
 Oocyte pass backdown the ovariole,then the each oocyte enlarges and leaves
the germarium .
 Finally it forms the follicular epithelium.
 Oocyte growth continues and the follicular epithelium keeps by cell division and
it becomes cuboid or columnar cells.
 As the oocyte grows the nucleus also increases.
 In some insects, fertilization takes place in the ovary in these maturation of the
oocytes is completed in the ovary.

23. VITELLOGENESIS
Deposition of yolk in the oocyte,occurs in the lower part of ovariole.
In some insects, vitellogenesis is completed in the late larva or pupa.
In most cases , a period of maturation required in adults before the eggs are ready
to ovulate.
The yolk categorised into protein yolk, lipid yolk and glycogen.
PROTEIN YOLK
Richest deposit of protein in the oocyte.
At the time of vitellogenesis, the follicle epithelium retracts from the surface of the
oocyte and gaps appears.
Then the haemolymph attached to the surface of the oocyte.
It takes up by pinocytosis. Pinosomes appearing in the cell membrane.
Then the cell membrane involves the rapid production.

24. LIPID YOLK
Arises in the oocyte in golgi apparatus.
Vesicles becomes filled with lipid ,grow and ultimately develop into lipid yolk
bodies.
Phospholipid droplets are present.
These droplets have triglyceride core and phospholipid sheath is present.
These droplets are utilized in the synthesis of yolk platelets.
GLYCOGEN
It is present derived from the trophocytes or follicle cells.
In some cases sugars are metabolized to from glycogen in the
trophocytes and the glycogen is then transferred into the
oocyte.

26. ENDOCRINE SYSTEM OF INSECTS
In insects many cells are modified to secrete hormones.
These hormones used for metamorphosis, moulting and reproduction
occur in insects.
In insect metamorphosis, the hormones are secreted to increases their
growth and metabolic activity of their body.
Some of the hormones sources are involved in insects are as
Neuro endocrine system
 Corpora allata
 Pro thoracic gland
 Epi tracheal gland
 Gut and ovaries

28. NEURO SECRETION IN INSECTS
 In insects nerve cells are modified to secrete hormones.
 These nerve cells are called neuro secretory cells.
 The secretions of neuro secretory cells are called neuro
secretions.
 These neuro secretion are temporaily stored in the special
structures called corpus cardiacum.
 It is well established that moulting and metamorphosis in
insects are controlled.
 It regulated by neuro secretions and hormones.

29. BRAIN HORMONE
 Brain contains groups of glandular cells called neuro secretory cells.
 These cells secreted a hormone called brain hormone.
 This hormone is transported by the axons of the neuro secretory cells
to a pair of lobe like endocrine glands.
 These glands are called corpora cardiaca.
 The corpus cardiacum releases the brain hormone into the blood.
 This hormone acts on a highly branched gland present in the
prothorax called prothoracic gland.
 In response to brain hormone, prothoracic gland secretes a hormone
called ecdyson.
 It brings about ecdysis or moulting.

30. JUVENILE HORMONE
 A pair of lobe like endocrine glands is called corpora allata.
 The hormone secreted by the corpus allatum is called juvenile
hormone.
 Its action retains the larval characters.
 The juvenile hormone acts in a curious way.
 As long as the hormone remains in the larva, the larva doesnot
differentiate into an adult.
 If a larva moults 4 times in its life and the 4th moult converts the larva
into a pupa , the juvenile hormone concentration will remain high
during the 1st three moults and it will decrease during the 4th moult.
 As a result, the 4th moult converts the larva into a pupa.

31.  When the corpora allata removed in the first stage
larva, the next moult converts the larva into a pupa
even though it has to go through three more moults in
normal development.
 When the corpora allata of a 4th stage larva are
transplanted to a first stage larva, the larva pupates
immediately.
 When the corpora allata of a 1st stage larva are
transplanted to a 4th stage larva ,the 4th stage larva
doesnot pupate, but it grows into a large larva for 3 or
4 moults and then only pupates.

32. Three hormones control the metamorphosis are
Prothoracictropic hormone
Ecdysone
Juvenile hormone[JH]
 Secreted by non neural endocrine cells.
 Prevent metamorphosis in the adult form.
 In adult stimulates sex attractant pheromones.

33. ADDITIONAL HORMONES
 Bursicaon hormone- darkening and
hardening of the cuticle.
 Edosion hormone- involves moulting
 Pre-ecdysis triggering hormone[PETH]
 Ecdysis triggering hormone[ETH]

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