Excretory organs in insects

The ppt covers-

EXCRETION SYSTEM
EXCRETORY ORGANS
TYPES OF EXCRETORY ORGANS
MALPIGHIAN TUBE
Histology
Function
LABIAL GLAND
NEHROCYTES
URATE CELLS
OENOCYTES
RECTUM/GUT
NITROGEN EXCRETION
CRYPTONEHRY
STORAGE EXCRETION

1. EXCRETORY ORGANS IN INSECTS

2. SYNOPSIS EXCRETION SYSTEM EXCRETORY ORGANS TYPES OF EXCRETORY ORGANS MALPIGHIAN TUBE Histology Function LABIAL GLAND NEHROCYTES URATE CELLS OENOCYTES RECTUM/GUT NITROGEN EXCRETION CRYPTONEHRY STORAGE EXCRETION

3. EXCRETION SYSTEM DEFINITION In living organism and cells the process of eliminating or expelling waste matter. It is the passive biological system that remove unnecessary materials from the body of an organism so as to help maintain internal chemical homeostasis and prevent damage to the body

4. EXCRETORY ORGAN Internal body organ and group of tissues and cells which perform excretion known by the excretory organ they are Kidney (human) Flame cells (flatworms) Urinary bladder In insects the function of excretion is chiefly concerned with the elimination of several types of substances such as mineral salts and water and products of the metabolism of nitrogenous substances , sulphur and phosphorus certain complex compounds that are produced incidentally as a result of certain accidents or as a by product in case of certain chemical changes and the acids and alkalis It is a process by which the internal environment of the insects is regulated at a constant level by removing surplus and injurious materials

5. TYPES OF EXCRETORY ORGANS MALPIGHIAN TUBE LABIAL GLAND NEPHROCYTES URATE CELLS OENOCYTES RECTUM AND GUT

6. THE MALPIGHIAN TUBE The main organ of excretion and osmoregulation in insects are the malpighian tubules .acting in association with rectum or ileum ORIGIN = they are outgrowth of the alimentary canal and consist of long thin tubules STRUCTURE = they are long, slender, blind tubules which are often convoluted NUMBERS = varies from group to group Anoplura – 4 Thysanoptera , hemiptera , diptera, siphonoptera – 4 to 6 Psocoptera and coleoptera – 2 to 8 Isoptera and lepidoptera ,trichoptera – 6 Odonata-50 to 100

7. COLOUR = white , yellow , cream coloured , smooth or beaded structure ABSENCE = they are absent in collembola and the family of aphididae of the order HOMOPTERA

8. Histology of Malpighian Tube The malpighian tubules are composed of two or eight cells and are of various shapes and sizes . They are either produced with distinct cell boundaries or are syncitial the cells are either smooth or have a brush or honey comb border towards the lumen the cells rest on a thin basement membrane covered by a peritonial membrane occasionally containing five muscle fibers which bring about the peristaltic movement of the tubules the movement caused by the muscles of the tubules assures the mixing of the contents .the tubules carries the contents towards the hind gut for find disposal

9. Function of Malpighian Tube This is chiefly excrete uric acid which is usually accompanied by water . The process of excretion takes place as follows The uric acid collected in the body cells diffuse into the blood which finally circulates round the malpighian tubules in the blood uric acid combines with sodium and potassium carbonates to form sodium and potassium urates . These two salts are soluble in water and are easily absorbed by the distal part of malpighian tubules in this way the urate salts are secreted into the lower of the malpighian tubules within the proximal part of tubule in alkaline pH by the action of carbonic anhydrates . The urate salts are broken down to regenerate water bicarbonates and uric acid the water and bicarbonates are reabsorbed and free uric acid is precipitated from here the uric acid solution loosely termed as ‘urine ‘ is passed into the proctodaeum and is finally excreted through the anus

10. It may be mentioned that this method of excretion involves a constant supply of water and in the majority of the insects .water is a very impotent constituent and can not be lost so easily In aquatic insects which are not compelled to conserve water excretion of uric acid accompanies a good deal of water . However in these to deprive the insects of essential ions such as chlorides sodium potassium . in order to eliminate this deficiency some aquatic larvae have a body covering which is highly impermeable to salts . The anal papillae can absorb the substances present in the fresh water OTHER ASCCESSORY FUNCTION Spittle secretion in spittle bug Light production in Bolitophila Silk production in larval neuroptera

11. LABIAL GLANDS In collembola and thysnaura where the malpighian tubules are absent. The labial glands are excretory in function , they have an upper sac like part a coiled labyrinth with a gland and excretory duct which opens at the base of labium The labial glands take up dyes from the blood and eliminate outside

12. NEPHROCYTES In some insects special cells . The nephrocytes perform the function of excretion . These cells are either pericardial cells distributed along the dorsal heart or garland like string of cells They also known by pericardial cells they are large and are often binucleate they are always found to have an acid reaction mesodermal in origin HOLLANDE (1922) give description about the pericardial cells. They are agents for breaking down complex colloids which are transformed by ferments produced in the cells into crystalloids

13. Urate cells Certain insects are provided with special cells in the body which become loader with crystalline spheres of uric acid .these cells are termed as urate cells They serve the function of excretion of uric acid and often of pigments also these urate cells are regarded as “storage” kidneys and are scattered throughout the insect body . These cells collect the uric acid in solid form through out the larval life and the excretory products are finally transferred to the malpighian tubules in the pupal stage for elimination e. g social hymenoptera

14. Oneocytes The cells of haemocoel epidermis or fat body with many functions Origin- ectodermal Present usually near the abdominal spiracles and sometimes remain closely associated with the bases of the epidermal cells They usually amber colored The functions of the oenocytes are still problematic they have been thought to secrete cuticular lipids but their ultra structure resembles that of vertebral cells concerned with steroid synthesis and it has even been suggested that they may be the site of ecdysone production

15. Excretion by Gut and Rectum According to WATERHOUSE and DAY tn collembola the mid gut performs the functions of excretion in case of aphids the excretory materials and the pigments are eliminated by the digestive tract in Periplaeta the uric acid is present in the form of crystals and not in liquid form in the wall of hind gut accordingly the hind gut does the functions of excretion to some extent in this insect some insects excrete ammonia which appears to pass directly into the digestive tract with out going to the malpighian tubules e.g. in blourflty larvae the ammonia is produced in the mid gut and is then reabsorbed and passed via blood to the hind gut. In aquatic insects the ammonia may be secreted directly into the rectum .

16. NITROGEN EXCRETION Terrestrial insects 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 “AMMO NOTELISM”

17. CRYPTONEPHRY The distal ends of the malpighian tubules are held in contact with the rectal by the perinehric membrane . Which is concerned either with efficient dehydration of faeces before their elimination or ionic regulation example larval symphyta

18. STORAGE EXCRETION The excretory waste materials are retained with in the body in different sites Uric acid is stored as urates in the cells of fat body e.g. – American cockroach Uric acid is stored in the body wall giving white color e.g.:- Red cotton bug Uric acid is stored in the male accessory glands to produced the outer coat of spermatophore which is excreted during copulation Uric acid is stored in the wing scales giving white color example butterfly