Digestive system
Digestion
Digestion is a process by which food and its ingested(cvK¯’wj‡Z MÖnbK„Z) form is easily broken down into assimilable(nRg †hvM¨) components throung the hydrolytic action of digestive systems. This process takes place in a specific organ system known as digestive tract
Digestive system
1. D. S is the system in which digestion take place
2. Another way we can say-DS is the system in which food is ingested and digested chemically, so that it can be absorbed into the blood and carried to the tissues where it is needed
Digestive system composed of two parts
1. Alimentary canal / Digestive tract
2. Salivary gland
Alimentary canal
It is tubular structure, somewhat coiled extends from mouth cavity to anus
It consists of three parts
Ø Foregut / Stomodeum
Ø Midgut / Mesenteron
Ø Hindgut / Proctodeum
Foregut/ Stomodeum
The position from mouth cavity to gizzard is called foregut. It consists of the following parts
Ø Mouth
Ø Pharynx
Ø Oesophagus
Ø Crop
Ø Gizzard
1. Mouth
This is the first portion of the foregut. Most of the insect take their foods thorough mouth.
2. Pharynx
It is a muscled organ lies in between mouth and oesophagus
Function
Ø It pushes the food material backward through oesophagus to crop
3. Oesophagus
It is nearly straight constricted (msKxb©) and tubular portion of the foregut leading to the sac like crop
Function
Ø It passes food material to the crop
4. Crop
It is the posterior (cieZ©x), dilated (mgcªmvwiZ) portion of the oesphagus
Function
Ø Temporary food storage and partial digestion
5. Gizzard
It is the terminal portion of the foregut. It provided with hard teeth, used to crush the food material. In between foregut and midgut there is a valve known as cardiac valve. Which protect regurgitation of food material from midgut to foregut.
Midgut or mesenteron
It is comparable to stomach of the mammals. It is lined with epithelial cells and there is no chitin. It is the principal side where most of the ingestion and absorption occur
1. Gastric caeca
A variable number of finer like outgrowth present in between foregut and midgut known as gastric caeca. It assists(mvnvh¨ Kiv) digestion of food material by producing enzymes
2. Malpighian tubules
At the junction of midgut and hindgut some finest cylindrical outgrowth present known as malpighian tubules
Functions
Ø It is a part of digestive system but act as a excretory organ
Hindgut
It is the last portion of the alimentary canal. It consists of
1. Ileum
It is the anterior (m¤§yLeZ©x) tubular portion of hindgut
2. Colon
It is the posterior tubular portion of hind gut
3. Rectum
It is also the posterior portion, the final section before anus,
Function of hind gut
The function of hindgut is to absorb salt and water
Salivary gland
Most of the insects have a pair of salivary gland. It is look like cluster of grapes and associated with labium. It consists of salivary lobes, salivary ducts and salivary cup.
Function
Ø It helps to digest food material by producing enzymes such as amylase, invertase , lipase, protease etc
Ø It helps to moisten mouth
Ø It acts as a solvent
Ø It helps to produce silk in Lepidoptera and hymenoptera
Ø It act as a glue in puparial cases
Physiology of digestion/ digestion and absorption of food materials
Information is available in sheet
Respiratory system
Respiratory system of an insect is a complex network of thin walled tubes called a tracheal system that delivers oxygen containing air to every cell as the body.
Responsibility of Respiratory system
Respiratory system is responsible for delivering sufficient oxygen to all cells of the body and for removing CO2 that is produced as a waste / end product or cellular respiration
Respiration:
Respiration comprises 2 processes
1. The process of respiration involving exchange of gaseous O2 into the insects and CO2 out into the environment
2. The repiratory metabolism whereby this O2 is combined with the substrate 2 produce energy and elimination of CO2.
Type of respiration:
Type of respiratory system depending upon habitat:
A. Terrestrial respiration
B. Aquatic respiration
C. Endoparasitic respiration
Terrestrial respiration:
Terrestrial respiration is divided into three system
1. Tracheal system
2. Ventilation
3. Elimination of CO2 from insect body
Trachea:
Trachea is the larger internal tube of the tracheal system. Each tracheal tube develops as a invegination of the ectoderm during embryonic development.
Tracheole:
The finer or smaller branches of the trachea which reach or extent to all parts of the body at the end of each tracheal branch, tracheole provides a thin, moist interphase for the exchange of gasses between atmospheric air and a living cell.
1. Spiracle
Air enters the insects body through bulb like external opening in the exoskeleton. These openings are called spiracles which are located laterally long the thorax and abdomen of most insects. Usually 1 pair of spiracles per body segments
2. Intima
The outer epicuticle with a protein / chitin layer beneath it called intima
3. Taenidium
A spiral thickening of the intima runs a long each tube, each ring of the spiral being called taenidium. It prevents the collapse of the trachea under pressure
Mechanism of Respiration in tracheal system:
O2 enters into tracheal tube through spiracles. After passing, oxygen in the tracheal tube first dissolves in the liquid of the tracheole and then diffuses into the cytoplasm of an adjacent cell. At the same time, CO2 is produced as a waste or end product of cellular respiration, diffuses out of the cells and eventually, out of the body through tracheal system
Ventilation:
It is the process by which air is brought into the tracheal system and circulated throughout the body
Spiracles
An ideal insect bears 10 pairs of spiracles. Two pairs of them are thoracic (meso, Meta) and remaining 8 pairs are abdominal (1-8 abdominal segments). Each spiracle bears a bulb or spkincter which regulates the inlet & exhaust of air. When insects remain in rest condition any two pairs of spiracles are opened. And remaining spiracles are closed but incase of active period all the spiracles are opened.
Ventilation in the tracheoles:
Gases go to the cell from tracheole through the walls of tracheoles by diffusion process
Elimination
Major portion of CO2 eliminated from the insect body is the help of integument and tracheae. Some of CO2 also eliminated through spiracles. In case of thick integument inter segmental membrane helps in discharge of CO2.
Aquatic respiration
Aquatic insects are equipped with a variety of oxygen with them under water or two acquire it directly from their environment. Due to adaptation aquatic respiration has been divided into the following types
1. Cuticular/ cutaneous respiration:
Lady aquatic insect species have a relatively thick integument that is permeable to O2. Diffusion of gases from this body wall is called cuticular respiration. Insect utilizes dissolved o2 from water and diffuses excess CO2 into the water. E.g. Early larval stages of Chironomous, simulium sp
2. blood gills
the body surface extend s and gives a very thin sac like structure which is blood field and contain some tracheoles. So, it is called Haemoglobin is a respiratory pigments that facilitate the capture of O2 molecule. E.g. larval stage of Chironomous
3. plasttoon respiration
Some fine hairs present on the ventral side of insect is called plastron hairs or hydrofuge hairs that create an air space next to the body. Air trapped within a plastron operates as a physical gill. When the insect consumes O2, it creates a partial pressure deficit inside the plastron; this deficit is corrected by dissolve O2 from the water. E.g. Riffle beetle (Elmis sp)
4. spiracular gills:
Filamentous outgrowth arises from the body wall which is hollow called lumen. This lumen filled up in water by diffusion mechanism and acts as a temporary air store. Lumen is connected with tracheal system. In this case insects take reserved O2 from lumen through tracheal system and perform respiration. E.g. pupa of Simulium
5. biological gill:
A biological gill is an organ that allows dissolves O2 from water to pass into an organism body. in insects, gills are usually outgrowth of the tracheal system with numerous trachea and tracheoles hence they are also known as tracheal gills. They are covered by a thin layer of cuticle that is permeable to both O2 and CO2
e.g. in may flies and Damsel flies, the gills are leaf like in shape and located on the sides of the abdomen. Fanning movements of the gills keep them in contact with a constant supply of fresh water
Endocrine glands and Hormones
Corpora= plural
Corpas =singular
Allata= plural
Allalum= singular
Endocrine organs:
The organs produce hormones which are generally released directly or indirectly via storage organ, into the blood, to various organs of the body known as endocrine organs
Exocrine organs:
The organs which secrete substances or ectohormone outside the body and these ectohormones are effective in the receiving organisms. E.g. wax glands, silk glands, scent glands, Dufor’s gland salivary glands etc. they produce pheromones and defensive secretions
Classification of endocrine organs:
1. Neurosecretory cells
2. specialized endocrine glands
3. corpora cardiac
4. corpora allata
5. prothoracic gland
Neurosecetory cells:
They are located in the ganglia of central nervous system. They form a link between endocrine glands and nervous system. Neurosecretory cells may either produce hormones, which act directly on effectors organs. They may act on other endocrine organs which are stimulated to produce hormones. The secretion of the neurosecretory cells promote the functioning of the prothoracic glands. Possibly control water loss oocite development and activity.
v Neupsecretory cells produce brain hormones or activation hormones
Specialized endocrine glands
Endocrine glands:
The gland s which are duct less in nature and give their secretions directly into the blood called endocrine glands
a. Corpora cardiac:
They are paired small organs lie immediately behind the brain. They store and release hormones from the neurosecretory cells of the brain
b. Corpora allata
They are pared, glandular bodies, located immediately behind the corpora cardiac. They are ectodarmal in origin. They produce Juvenile hormone which regulates metamorphosis and yolk deposition in the egg
c. Prothoraic gland
They are paired flattened and diffused organs lying close to the prothoracic spiracles. They are ectodermal, glandular and larval organs being lost in the adult
Function
They produce molting hormones ecdysone which regulates molting in insects
Ring gland:
In the larval of cyclorhaphous dipteral, the corpora cardiac, corpora allata, and prothoracic glands are all fused into a single structure called ring gland or cueismanis ring.
Hormone:
Hormones may be defined as the physiologically active substances that are produced by endocrine glands of the organism in-self and excretes their effects away from their side of origin, being transported by the body fluid.
Type of Hormones
1. Activation / Brain hormones
2. Juvenile hormones
3. Molting hormones/ ecdysone
Hormonal control of metamorphosis
During growth and development, insects pass through a number of larval instars (Holometabolar) before becoming an adult. This transition is brought about by the combined and co-ordinated action of the three hormones like activation hormone, juvenile hormone molting hormone. The progressive development of larval characters takes place in the presence of juvenile hormones. The changes occurring at successive molts are controlled by the timing and quantity of molting hormone secreated. The concentration of juvenile hormone will be much lowers in later larval instars them in the early instars. Due to low concentration of juvenile hormone in last larval instars the larva molt into pupa and in absence juvenile hormone the pupa moves into adult. In hemimetabolar the ultimate instars nymph molts directly in the adult in absence of juvenile hormone
Blood circulatory system
Definition
The system by which blood is continuously circulated through the insect’s body is known as BSS. It is open type
Open type blood circulatory system
The blood circulatory system which expended into body cavity is known as Open type blood circulatory system. E.g. blood circulatory system of insect
Close type blood circulatory system
The blood circulatory system which consist of vein, arteries, capillaries and heart itself
Blood
The clear fluid which is circulated through the body cavity is called blood. It is colorless, often tinged with green or yellow pigments. Exception red color blood is found in Gall midge larvae due to presence hemoglobin. It consists of liquid part, plasma and blood cell (haemocytes)
Chemical composition of insect blood
1. Water
Water is the major components of internal body fluid. It ranges from 84-92% of the total body weight
2. Inorganic constituents
Na, K, Ca, Mg, P, CO3 are the major inorganic constituents. In addition Fe, Cu, Al, Zn and Mn are also found in insect’s blood.
3. Carbohydrates
Glucose, fructose and ribose are major carbohydrates present in blood. In addition Glycogen, glycerol is also present
4. Lipid
Lipid present in blood in minute amount, either small fat particles or in lipoprotein
5. Amino acid
Free amino acids present in hemolymph is one of the important character in the class insecta. It is either dietary or synthesized by insects
6. Enzymes
Protease, lipase, sucrose and amylase are present in insect’s blood.
7. Pigments.
Hemoglobin, Kathymoglobin, carotene and xanthophylls are present in insect’s blood.
8. Gases
Both O2 and CO2 present in insect blood.
9. Metabolic waste
Function of insect blood
1. Movement of materials
Insect blood is responsible for movement of nutrients, salt, hormones and metabolic wastages throughout the insect body
2. Lubricants
Hemolymph, the circulating fluid that bathes various tissues of the insect body serves as a lubricant allowing easy movement of the internal structure
3. Hydrostatic pressure
Hydrostatic pressure generated internally by muscle constraction used to facilated molting hatching, expansion of the body and wings after molting, physical movement (specially soft bodied larvae), reproduction (insemination and oviposition), evagination of exocrine glands
4. Thermoregulation
Insect blood helps to cool the body of the insect by conducting excess heat away from active flight muscles or warm the body by collecting and circulating heat absorbed while basking in the sun.
5. Storage
Hemolymph or blood serves as a storage cool for raw material for the production of new cells
6. Defense
a. Phagocytosis
Bold ingest foreign particle of various sorts; bacteria and cellular debris. The phagocytic role is important in some instance for the protection of insect from caviar infection by microorganisms
b. Encapsulation
Encapsulation is a protecting mechanism by which inhabit internal parasite and other invaders
c. Detoxification
Insect blood is capable of rendering toxic substances and insecticides to non-toxic
d. Wound
It seals wound through clotting reaction
e. Co-agulation
Blood helps in coagulation of bleeding
Blood circulatory system consist of
1. Dorsal vessel
2. Accessory pulsating organ
Dorsal vessel
It is the major structural component of insect’s blood circulatory system. This tube runs longitudinally through the thorax and abdomen, along in site the body wall; in most insects it is fragile, membranous structure that collects hemolymph and conduct toward the head. Dorsal vessel consist of
a. Heart
b. Aorta
Heart
Heart is a tubular structure lies dorsally with muscular wall and with a series of lateral opening called Ostia through which blood enter into the heart chamber. It is divided into compartment corresponding to the segments of the body of insects. A pair of alary muscle is attached with each of the chamber
Aorta
Anterior portion of the heart the on-chambered part is called aorta. It starts from heart and open into the head
Accessory pulsating organ
It helps to circulate blood in insect body. It consist of
1. Thoracic pulsating organ
It circulate blood in the wing of the thoracic organ
2. Ventral diaphragm
It helps to circulate blood in the different parts of the insect body by expansion and relaxation. It develops over ventral nerve coard.
Mechanism of blood circulation
Circulation of blood in insect body is occurs in two ways
1. Systole
2. Diastole
Blood circulate in the different parts of the insect body by expanding and contraction of heart wall and alary muscle. Each chamber of the heart expanded and contracted from back to forth. During expansion the Ostia open and blood enter into the heart chamber. During contracting the Ostia are closed and blood move forward and discharged into the head. From head blood again discharge different parts of the insect body
Fig. Blood circulatory system
Excretory organ / system
Excretion
The waste product of metabolism either or of no value to the organisms or if allowed to accumulate in the body it would be harmful. The process of elimination of these waste products from the body is known as axcretion
Excreta
The substances that are eliminated through the process of excretion is known as excreta
Excretory system
The system by which waste products of metabolism comes out from the body is known as / called excretory system
Functions of excretory system/ Excretion
1. To maintain ionic balance of the insect body
2. To regulate water in insect body
3. To remove unwanted substance from insect blood( Hamelin )
4. Retention of constituents needful to the organism
Types of excretory products
1. Solid : nitrogenous an non nitrogenous compounds and inorganic salts
2. Liquid : Mainly water
3. Gaseous: Mainly Co2
The end products that are eliminated through the process of excretion
1. End products of nitrogen
2. End products of S and P compounds
3. Byproducts of some miscellaneous(wgwkªZ) chemical reactions
4. Acids and basis
5. Salts and water
Excretory organ
Excretory organ that is involved in the process of excretion
a. General body integument
b. Certain specialized part of the integument (integument gland)
c. The wall of the alimentary canal
d. Cephalic excretory organs
e. Storage excretory organs
f. Chief excretory organ
E.g. Malpighian tubules
General body integument
Body integuments of many insects serve as an excretory organ, in the elimination of waste products including nitrogenous substances and inorganic salts. Cuticle consists of 30-40% chitin which is a nitrogenous polysaccharide. The cuticle is periodically cast of (S‡i c‡o) and renewed during molting process. By this process insects losses a large amount of nitrogen
Certain specialized part of the integument (integument gland)
Ectodermal glands (ectodermal glands are opening) are present in some insects very close to the anus which act as a excretory organ. E.g. Rice bug
The wall of the alimentary canal
Accumulation of crystalline body occurs in the wall of the mesenteron. Most of the salts are of Ca; these are either excretory products or excess substances. Excretory products are also be eliminated directed through the wall of proctodeum
Cephalic excretory organ
a. Labial gland
Labial glands of Collemblola and Diplura discharge Amonia carmine by means of excretory dust which opens at the base of labium. It consist its upper region a saccule flattened with epithelium and communicating with long coiled tube or labyrinth.
b. Salivary gland
Dolycoris and heteropteran insects can absorb and utilize L-valine (Amino acid) but not D-valine and excrete from the body
Storage excretory organ
a. Nephrocytes cells
Nephrocytes are cells that uptake foreign chemical of high molecular weight and excrete from the body
Nephrocyte cells are found on the surface of the heart known as pericardial cells.
b. Urate cells
In collembola lack of malpighian tubules granules of uric acids are collected by certain cells known as urate cells. The cells become increasingly lobbed with concentration with the increase of age of the insect; in larvae the cells are appear as white point dotted among the cells of fat body.
Chief excretory organ
At the junction between midgut and hindgut some long, slender, finest, thin walled tubules present known as malpighian tubules. These tubules lie in haemocoel and freely attached with blood. An Italian, Marcello Malpighi discovered malpighian tubules in 1969. The number of malpighian tubules varies in insect. As for example in collembolan number of malpighian tubules
1. Coleopteran, 4-6
2. Lepidoptera,6
3. Plecoptera, 30-50
4. Matids, 100
5. Blattids, 80-100
6. Odonata, 50-60
7. Lonustids, 100
Functions of malpighian tubules
1. Urea, uric acids are the chief metabolic wastes eliminated by malpighian tubules
2. Vitamins like riboflavin, thiamin, Niacin, pantothenic acids are believed to be synthesized symbiotically in the MT like in Periplaneta americana
3. MT excrete some inorganic waste products such as carbonate and oxalate of Ca
4. Excess carbohydrates are eliminated as honey dew in some homoptera
5. MT act as a reserve of water continent (gnv†`k)in some beetles
6. Modified cells of MT in some crysomelide, Agelastica alni secrete sticky fluid which helps in locomotion
7. These sticky substances helps in the preparation of protective Ootheca for the eggs
8. Silk is produced by malpighian tubules in chrysopa and in some larvae of hymenoptera
How malpighian tubules work
Working system of MT
Uric acids in body cell diffused into blood and circulated around the malpighan tubules. The MTs absorb this uric acid and discharge the aqueous solution of the lumen. From this part the uric acid solution, forced into the proctodeum and discharged by anus
Physiology of excretion
Nervous system
Nervous system
Nervous system is a network of specialized cells (Neuron) that serve as an information highway within the body. These cells generate electric impulses(Zvobv) that travel’s as the wave of depolarization (‡giy cÖeYZv )through the cell membrane
Neuron
The unit of the nervous system is called neuron
Neuron has the following elements
Nucleus + mitochondria + others
Classification of neuron
A. On the basis of their structure neuron cab be classified into there categories
1. Monopolar neuron
2. Bipolar neuron
3. Multipolar neuron
B. On the basis of functions neuron can be classified into three categories
1. Afferent(wfZigyLx) neuron (Sensory neuron)
Bipolar or multipolar cells have dendrite that is associated with sense organs or receptors that carry information toward the central nervous system
2. Efferent neuron(ewng©yLx) (Motor neuron )
Unipolar cells that conduct signals away from the central nervous system that stimulate responses in muscles and glands
3. Internuncial( association )
Unipolar cells that conduct signal within the central nervous system
Ganglion (singular)
A cluster of interconnected neuron that process sensory information or motor outputs
1. Choline choloride
2. 5-hydroxy tryptamine
3. Dopamine
Central nervous system
Insects have a central nervous system with dorsal Brain linked to ventral nerve cord that consist of paired segmental ganglia runs through the ventral surface of the thorax and abdomen
Each of the ganglions is connected by short medial nerve known as Commissure and also jointed by intersegmental connectives two ganglia in the adjacent body segments. The CNS is compared to a ladder where commissure is the rung (g‡qi avc)of the ladder and inter segmental connectives are the rails (`Ûwe‡kl, †eovi LyywU)
We know, there are three major parts of a central nervous system, these are
1. Brain
Brain is a complex organ with six (6) fused ganglia each of which has limited spectrum (eY©vjx)of activities. These are nine principle nerves found in Brain
a. Proto-cerebrum
The first pair of ganglia is largely associated with vision(`„wó, Kíbv). They innervate(Drmvn ‡hvMvq) compound eyes and ocelli
b. Deutocerebrum
The second pair of ganglia that process information collected by antenna
c. Trico cerebrum
Third pair ganglia are associated with labrum and integrate(mgMÖZv `vb Kiv) sensory input from protocerebrum and deutocerebrum
They also link brain to the rest part of ventral nerve cord and with other nervous system that control internal process
2. Sub oesophageal ganglion
Innervate not only labium, mandibles, maxillae but also hypopharynx, salivary gland and neck muscles
3. Ventral nerve cord
a. Thoracic ganglia
A series of ganglia lie in the floor of thorax and abdomen. Ganglia that remain in thoracic region are known as thoracic ganglia. They control locomotion by innervating legs, wings sensory organs and muscles
b. Abdominal ganglia
They are varying in number. They control the movement of abdominal muscles
Visceral nervous system
1. Stomatogastric nervous
In various nervous system it is includes frontal ganglia, recurrent verve, hypocerebral ganglion, a pair of inner and outer oesophageal ganglia. They innervate foregut and midgut of the alimentary cannel of an insect
2. Median ventral nerve
Which arise from ventral midline of the thorax and abdomen and innervate (each) both sides of the spiracles?
3. Caudal sympathetic nerve
Which arise from terminal end of the abdominal ganglion. They innervate sex organ
Peripheral nervous system
It refers to all nervous systems other than central nervous system. They carry signals to (from) the central nervous system and make the movement of the muscles and body of the insect
Peripheral nervous system is of two types
1. Motor
They make the body parts move in response to the signals from the brain and
2. Sensory
That carries signals to the brain
Reproductive system
Reproduction
The process by which new individuals or offspring is produced from parents is known as reproduction. The power of reproduction is the fundamental property of living beings. Most of the cases insects are bisexual in reproduction. As their bisexual, offspring is produced form two adult insects of opposite sexes.
Types of reproduction
1. Sexual reproduction
2. Asexual reproduction
Sexual reproduction
This is the normal type of reproduction which ultimately depends on mating or copulation of two adult insects of opposite sexes. The fertilization of female gamete by male gamete then fertilized female e gametes form zygote, which develop into new individual or offspring
Fertile (Fertilized) female gamete 
Fertilization
Offspring
Fig. sexual reproduction
Asexual reproduction
It is an exceptional type of reproduction in which / where female insects contribute to produce new individual or offspring
Type of sexual reproduction
1. Oviparity
2. Viviparity
Oviparity
This is the most common type of sexual reproduction in which mating or copulation of two insect of opposite sexes occurred. After mating / copulations female insect laid fertilized egg which hatched after deposition. Here, the yolk of the egg supply nutrient to the developing embryo. viviparous – jack fruit
Viviparity
This is exceptional type of sexual reproduction in which female insect produces nymph or larvae instead of laying eggs
Types of viviparity
1. Ovo viviparity
2. Adenotrophic viviparity
3. Haemocelous viviparity
4. Pseudoplacental viviparity
Ovo viviparity
In this type of reproduction the development of embryo occurred inside the body. The yolk of the egg supply nutrient upto hatching then maternal deposition occurred. No extra nutritive structure form developed here.
This type of reproduction is found in muscidae and Blattidae family.
Adenotrophic viviparity
In this type of reproduction yolk of the egg nourish the developing embryo up to hatching. After hatching the nymph or larva remain in muscular enlarged part of the vagina, within uterus and feed on uterine milk produced by a mass number of accessory gland
E.g. pupipara fly (piptera)
Haemocelous viviparity :
In this type of reproduction eggs or Oocytes directly released in the haemocel. The developing embryo takes nutrient from haemolymph. After hatching the nymph or larvae escape through genital opening. E.g. stripsiptera
Pseudoplacental viviparity
In this type of reproduction the embryo developed in the enlargement part of the vagina. The developing embryo take nutrient placentas like structure originated from enlarge part of the vagina, known as pseudoplacenta. E.g. Psocoptera and Dermaptera
Types of asexual reproduction
1. Parthenogenesis reproduction
2. Paedogenesis reproduction
3. polyembryony reproduction
4. Hermaphroditism reproduction
Parthenogenesis reproduction
When reproduction occurs without the help of male is known as parthenogenesis reproduction. Eggs undergo full development without fertilization and give rise to new offspring or individual.
Different types of parthenogenesis reproduction
a. Sporadic parthenogenesis
When reproduction occurs occasionally but occurs bisexually, then this type of reproduction is called sporadic parthenogenesis. E.g. silk worm moth, locust
b. Cyclic parthenogenesis
When parthenogenesis and bisexual reproduction occurs in an alternate way is called cyclic parthenogenesis. E.g. aphid
c. Constant parthenogenesis
When reproduction occurs only parthenogenetic way that means parthenogenetic way is only the normal mode of reproduction is called constant parthenogenesis. E.g. stick insect
d. Arrhenotokus parthenogenesis
When unfertilized eggs develop only male offspring, this type of parthenogenesis, is called arrhenotokus parthenogenesis. E.g. Hymenopteran insects
e. Thelytokus parthenogenesis
When unfertilized eggs develop only female offspring, this type of parthenogenesis is called thelytokus parthenogenesis. E.g. Phasmida insects
f. Amphitokus parthenogenesis
When unfertilized eggs develop both male and female offspring, this type of reproduction is called amphitokus parthenogenesis. E.g. Hymenopteran insects
g. Haploid parthenogenesis
When offspring contain half of normal chromosome in their somatic cell, this type of reproduction is called haploid (reproduction) parthenogenesis. E.g. Aphids
h. Diploid parthenogenesis
When offspring contain double number of chromosome in their somatic cell, this type of reproduction is called diploid parthenogenesis
Paedogenesis reproduction
When reproduction is affected by juvenile stage, then this type of reproduction is called paedogenesis. In this reproduction immature stages larva or pupa posses functional ovary in which eggs developed parthenogenetically later on give rise to new offspring. E.g. Rice gall midge
Polyembryony reproduction
When more than one embryo developed from a single egg, then this type of reproduction is called polyembryony reproduction. Eggs undergo mitotic division and develop more than one embryo which developed new offspring or individuals. E.g. Brachonidae, callcidae, Echnidae family.
Hermaphroditism reproduction
When male and female sex organ present in the same individual, this individual is called “Hermaphrodite” and if reproduction occur is called hermaphroditism. Hermaphrodite never copulates with other hermaphrodite. This type of reproduction is called hermaphroditism reproduction. E.g. scale insect of California
Spermatogenesis
Spermato- spermatozoa
Genesis – reproduction
The process by which spermatozoa are developed in a testicular follicle is called spermatogenesis
Step of spermatogenesis
On the basis of spermatogenesis testicular follicle are divided into four different zones.
1. Germanium / Zone of spermatogonia
2. Zone of growth / zone of spermatocytes
3. Zone of maturation & reduction/ spermatids
4. Zone of transformation/ spermatozoa
Germanium / Zone of spermatogonia
Apical portion of the testicular follicle comprises of germ cells i.e. spermatogonia. It also includes a large cell known as apical cell which act as a nutritive cell.
Zone of growth / Zone of spermatocytes
In this zone spermatogonia undergo successive mitotic divisions. Resulting size number is increased. In this zone spermatogonia are encysted by follicular epithelial cells. It’s called spermatocytes
Zone of maturation and reduction / spermatids
In this zone the dipoid spermatocytes undergo successive reduction division and produce haploid daughter cells. In first and second reduction divisions primary and secondary spermatids are produced respectively.
Zone of transformation / spermatozoa
The basal portion of the testicular follicle comprises of spermatozoa. In this zone secondary spermatids are converted into flagellated spermatozoa. Then the cyst ruptured and the spermatozoa are released
Fig. Different stages of spermatogenesis
Oogenesis
The term includes all those process which develop mature or ovum is called Oogenesis. On the other hand, we can say the process by which egg or egg cells attain maturity in the ovariole or ovarian tube is called Oogenesis
Like testicular follicle ovariole is divided into different zones which comprise of primary germ cell i.e. Oogonia. The ovariole is divided into two zones
1. The apical germarium and
2. The basal vitellarium
The apical germarium
This zone comprises of female germ cell i.e. Oogonia which undergo successive mitotic divisions and give rise to primary Oocytes and nutritive cells which furnish nutrient to the developing Oocytes. This Oocytes move to basal portion of the ovariole by repeated mitotic division.
The basal vitellarium
In this zone primary Oocytes are surrounded by follicular epithelial cells. In these zones the spermatocytes accumulated yolk. The process of accumulating yolk is called vitellogenosis. The egg or ovum attain maturity undergo reduction divisions. The most mature eggs or ovum move to lateral oviduct is called ovulation
Types of ovariole
1. Panoistic type
2. Polytrophic type
3. Telotrophic type
Panoistic type
Nutritive cell absent /wanting in it. These types of Ovariole are found in the order Orthoptera, Dermaptera, Dicyoptera.
Polytrophic type ovariole
Here nutritive cell present. This type of ovarioles is found coleopteran, hymenoptera, Lepidoptera, dipteral.
Telotrophic type ovary
Here nutritive cord present. E.g. Hemiptera and colleoptrera
Molting
The process by which insect shade their cuticle or exskellaton is called moulting. Moulting hormone or ecdysone is responsible for moultin process
Function
1. For growth and development of insect body
2. To change their live stages
3. To accommodate new tissues
Steps of molting
The histological and other changes accompany with molting process are summarized by Richard (1951) are as follows
1. Insect stop feeding and become inactive for a short period of time
2. The epidermal cell enlarge and divide mitotically
3. The old cuticle become detached from the epidermis
4. The space between old and new cuticle filled up with molting fluid containing 2 enzymes; protease and kitinase
5. These two enzymes dissolve endoculicle and the product is digested by epidermal cells and absorbed.
6. The old cuticle is ready to shed.
7. Construction of abdominal muscles.
8. Split out the old cuticle from the head and thorax of the insect and new instars comes out
9. Hardening and darkening of the new cuticle
Terminology
1. Instar
The actual form o insect during stadium and immerge upto 1st molt is called instar
2. Stadium
The time period between two successive instar
3. Stage
Distinct phase of insect life
4. Imago
Fully develop insect is called imago
5. Sub-imago
Pre-adult insect in which reproductive organ is not fully developed.
Fig: molting cycle
Nutrition
Nutrition is the study of food requirement of the organism, in this case insect. This studies many include the essential component of the diet or may be expanded to include those substances that produce energy in the most efficient way. Food ingested and digested must fulfill the nutritional requirement of insects for growth and development
Food constituents can be classified into two groups
1. Essential
2. Non essential
Essential
It inclused those components that must be included in the normal died become they cannot be synthesized either by metabolic process ir the normal complement of the symbionats. E.g. vitamins mineral and certain salts
Non-essential:
It includes those components that must be consumed the produce energy and may be converted into a form that can be utilized in metabolic process. E.g. carbohydrate, proteins, fate
Nutritional requirement of diets
1. Carbohydrate
CHO serve as a source of energy and may be converted into fat or storage may contribute for the production of Amino acid. They often form the essential part of the diet and are required in large amount. The utilization of CHO depends on the ability of insect species to convert polysaccharide and oligosaccharide into assailable into simple sugar
In order of utilization CHO include:
Dextrin, fructose, fructose, maltose, mannital, raffinose, sorbital, starch, sucrose and trehalose
2. Protein and Amino acid:
Protein is a complex organic molecule consists of a series of amino acids. They are the principal component of animal tissues. From nutritional stand point the requirement of protein is the requirement of individual amino acid. About 21 amino acids are found in natural protein essential. The essential amino acids are
Lysine, leusine, isoleusin, metheonine, threonin, valin, tryptophan, phenyl alanine, Arginin and Histidin
3. Nucleic acid (nutritional requirement)
Nucleic acid present in cell as DNA or RNA exhibit ever increasing number of metabolic process. Tit has been demonstrated that addition of RNA increasing the growth rate of dipterans insect.
4. Vitamins
Vitamin is an organic molecule required in minute amount for growth and normal functioning of ell. They play an important role in metabolic process in which they act as a part of enzyme. It is conceded that water soluble group such as Riboflavin, Thiamine, and Niacin, pantothanic acid, Biotin and cyanocobal amine for most of the insects. Besides this other vitamins
v Vitamin BT(carnitine)= for growth and development
v Vit-C (ascorbic acid)=Helps in molting process
v Provitamin A (carotene)= visual normal pigmentation
v Vit-E(