Lecture 10: Excretory System in Insects
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Questions and Answers

What is the main function of the Malpighian tubules in insects?

  • Excretion and osmoregulation (correct)
  • Digestion of food
  • Respiration
  • Reproduction
  • What is the purpose of the peritoneal coat and muscle fibers surrounding the Malpighian tubules?

  • To filter out solutes from the haemolymph.
  • To provide structural support and aid in peristalsis. (correct)
  • To absorb water and solutes from the primary urine.
  • To secrete enzymes for digestion.
  • What is the relationship between the Malpighian tubules and the alimentary canal in insects?

  • The Malpighian tubules are part of the alimentary canal.
  • The Malpighian tubules are completely separate from the alimentary canal.
  • The Malpighian tubules are connected to the mouth of the alimentary canal.
  • The Malpighian tubules act in association with the rectum or ileum of the alimentary canal. (correct)
  • How many Malpighian tubules are present in different insects?

    <p>60 in cockroaches</p> Signup and view all the answers

    What is the relationship between the primary urine produced by the Malpighian tubules and the haemolymph (insect blood)?

    <p>The primary urine is isosmotic to the haemolymph but ionically dissimilar.</p> Signup and view all the answers

    What is the primary function of the excretory system in insects?

    <p>To remove waste products of metabolism, especially nitrogenous compounds</p> Signup and view all the answers

    Which of the following is NOT considered a major excretory organ in insects?

    <p>Tracheal system</p> Signup and view all the answers

    What is the primary function of the Malpighian tubules in the insect excretory system?

    <p>To regulate the salt, water, and nitrogenous waste excretion</p> Signup and view all the answers

    What is the function of the nephrocytes (pericardial cells) in the insect excretory system?

    <p>To sieve the haemolymph for products that they metabolize</p> Signup and view all the answers

    What is the role of the fat bodies in the insect excretory system?

    <p>To store and excrete excess nutrients and waste products</p> Signup and view all the answers

    Which of the following is NOT considered an excretory organ in insects?

    <p>Tracheal system</p> Signup and view all the answers

    Which of the following describes the excretion process in terrestrial insects?

    <p>Conserve water and excrete concentrated or dry wastes</p> Signup and view all the answers

    What is the primary function of osmoregulation in insects?

    <p>Maintain favorable osmotic pressure and ionic concentration in body fluids</p> Signup and view all the answers

    Which ions do both terrestrial and aquatic insects need to conserve?

    <p>Sodium (Na+), potassium (K+), and chloride (Cl-)</p> Signup and view all the answers

    What is the role of chloride cells in the insect excretory system?

    <p>Absorb inorganic ions from dilute solutions</p> Signup and view all the answers

    In freshwater insects, what is regulated in response to the loss of ions to the surrounding water?

    <p>Hemolymph composition</p> Signup and view all the answers

    What is the major anion found in the isosmotic filtrate in malpighian tubules?

    <p>Cl-</p> Signup and view all the answers

    What generates an osmotic pressure gradient in malpighian tubules for the passive flow of water?

    <p>Active transport of K+</p> Signup and view all the answers

    What type of excretion is seen in terrestrial insects such as coleoptera and lepidoptera larvae?

    <p>Uricotely</p> Signup and view all the answers

    In aquatic insects, what is the excretory product that requires more water for waste removal?

    <p>Ammonia</p> Signup and view all the answers

    What holds the distal ends of the malpighian tubules in contact with the rectal wall?

    <p>Perinephric membrane</p> Signup and view all the answers

    Which accessory function is NOT associated with malpighian tubules?

    <p>Saliva production in adult coleoptera</p> Signup and view all the answers

    Study Notes

    Excretory System of Insects

    • The excretory system in insects is responsible for removing waste products of metabolism, particularly nitrogenous compounds, and maintaining salt-water balance and physiological homeostasis.

    Malpighian Tubules

    • Malpighian tubules are the main organ of excretion and osmoregulation in insects.
    • They are thin, blind-ending tubules that originate near the junction of the mid and hindgut.
    • Each tubule is covered with a peritoneal coat and supplied with muscle fibers that aid in peristalsis.
    • The distal secretory region and proximal absorptive region of the tubules work together to produce a filtrate (primary urine) that is isosmotic but ionically dissimilar to the haemolymph.

    Functions of Malpighian Tubules

    • Remove nitrogenous wastes
    • Regulate salt, water, and ion balance
    • Produce a filtrate (primary urine) that is isosmotic but ionically dissimilar to the haemolymph
    • Accessory functions include spittle secretion in spittle bugs and light production in Bolitophila

    Other Excretory Organs

    • Nephrocytes: cells that sieve the haemolymph for products they metabolize
    • Fat bodies: loose or compact aggregations of cells that store and excrete waste products
    • Oenocytes: specialized cells with many functions, including excretion
    • Integument: outer covering of the insect body that aids in excretion
    • Tracheal system: insect gas exchange system that also aids in excretion
    • Rectum: posterior part of the hindgut that modifies urine to maintain fluid and ionic homeostasis

    Excretion and Osmoregulation

    • In aquatic insects, haemolymph composition is regulated in response to ion loss to the surrounding water.
    • Special cells called Chloride cells in the hindgut absorb inorganic ions from dilute solutions.
    • Active transport of ions generates an osmotic pressure gradient for the passive flow of water.

    Nitrogenous Excretion

    • Terrestrial insects excrete waste products as uric acid or urates (uricotelism), which requires less water for waste removal.
    • Aquatic insects excrete ammonia, which requires more water for waste removal (ammonotelism).
    • Cryptonephry is a specialized structure in some insects that aids in efficient dehydration of faeces or ionic regulation.

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    Description

    Learn about the excretory system in insects, focusing on the removal of waste products and maintenance of salt-water balance. Explore the functions and structures of excretory organs such as Malpighian tubules, nephrocytes, and more.

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