EXAM #2

Question 1

What are the nutritional requirements of insects?

Answer 1

Aminoacids
Carbohydrates
Lipids
Vitamins

Question 2

What are the nutrients insects cannot synthesize?

Answer 2

Essential aminoacids and some lipids (sterols)

Question 3

Usually, are the nutritional requirements the same throughout the life stage of an insect?

Answer 3

Not usually. Nutritional requirements differ at different life stages. (adults do not often feed).

Question 4

Many insects feed on unbalanced or nutritionally poor foods. What kinds of adaptations do insects show for obtaining proper balance of nutrients?

Answer 4

Insects show behavioral, physiological, and ecological adaptations (endosymbionts, microorganisms in the gut that help to provide nutrients to the insect)

Question 5

What are some of the insect diets? What is the relationship between diet and morphology?

Answer 5

Insects can feed of xylem and phloem; blood; bacteria and algae; plant material; animal material; wood. Diverse diets correspond to diverse mouthparts and gut structure. Some insects cross categories. Different life stages often require different diets.

Question 6

What is digestion? How does it happen?

Answer 6

Digestion is the polymer break up into monomers constituents so they can be absorbed. It occurs as food moves through the simple tube of the alimentary canal. This is accompslished mostly by enzymes through hydrolisis.

Question 7

What is the foregut role in digestion?

Answer 7

Mastication and storage take place in the foregut. Some digestion occurs through the release of saliva. Proventriculus regulates flow into midgut.

Question 8

What is the midgut role in digestion?

Answer 8

The main role of the midgut is digestion and absorption of nutrients. Production and secretion of digestive enzymes take place into the midgut, which is the only section not lined with cuticle.

Question 9

What are the roles of the gastric caeca and peritrophic membrane in the midgut?

Answer 9

Gastric caeca increases the surface area. Peritrophic membrane surrounds the food and separates it from midgut epithelium, providing protection against abrasion and pathogenes.

Question 10

What is the hindgut role in digestion?

Answer 10

Absoption of water and salts as well as excretion through feces and urine.

Question 11

What is the role of microorganisms in digestion?

Answer 11

Nutrients supply (sterols, aminoacids, and vitamins) for insects feeding on nutritionally suboptimal food (bacteria/bacteroids/unicellular fungi/protozoa)

Question 12

Role and location of extracellular symbionts?

Answer 12

Free in gut lumen. Can be found on pockets in midgut and hindgut. For instance, termite hindguts contains bacteria and fungi that help digest lignocellulose and nitrogen fixation. These microorganims are trasmited by oral uptake or from excreta of other individuals.

Question 13

Role and location of intracellular symbionts?

Answer 13

Housed in symbiont-containing cells denominated mycetocytes or bacteriocytes. Very common, many are examples of mutualism. They are transferred to eggs. In aphids, buchnera supplies essential aminoacids.

Question 14

What are the organs involved in excretion? Whate are their function?

Answer 14

Malpighian tubules (filtration of hemolymph) and hindgut (reabsorption of ions and water).

Question 15

General role of excretory system?

Answer 15

Homeostasis, which includes elimination of harmful substances that interact will cells and tissues; Osmoregulation.

Question 16

How is waste eliminated?

Answer 16

Through urine (result of metabolism in body proper) and frass (feces – unmetabolized substances).

Question 17

Steps of the production of primary urine by malpighian tubules?

Answer 17

1 - Proton pump secrets H into lumen of tubules against an electrochemichal gradient (requires ATP/oxigen).
2 - K ions in hemolymph enter tubules epithelial cells through K gates. Water flows passively. The resulting gradient powers K/H antiporter.
3 - K in secreted into lumen against electrochemical gradient.
4 - Dissolved molecules (sugars, nitrogenous waste, etc) follow osmotic gradient.
5 - Primary urine is isosmotic to hemolymph but ionically dissimilar - its a selective filtrate: high in K, low in Na and Cl,

Question 18

How does the selective reabsoprtion works in the hindgut?

Answer 18

Primary urine flows to hindgut: ileum, colon, and rectum. In hindgut, some substances actively reabsorbed into hemolymph, some substances actively secreted. Hindgut aligned with a more permeable cuticle, and epithelial cells adapted for secretion and absorption. Rectal pads are present (specialized groups of cells for absorption, many conecntions with tracheoles, many mitochondria).

Question 19

Selective reabsoprtion: ileum and rectum role?

Answer 19

In ileum and rectum, ions are actively reabsorbed with Cl pumps the driving mechanisms. Water flows passively.

Question 20

What does homeostasis maintain in the the excretory system?

Answer 20

Constant internal environment in cells, tissues, and fluids. Electrolyte/ion (blood-feeding insects), water (important in terrestrial insects), and nitrogen (excretion of N) homeostasis.

Question 21

Discuss the cryptonephridial system as an adaptation to conserve water.

Answer 21

Distal ends of malpighian tubules in contact with rectal wall by peripheric membrane. This adaptation for conserving water is more developed in insects that feed on drier diets.

Question 22

Roles of diuretic and antidiuretic hormomes?

Answer 22

Diuretic hormones are neuropeptides that interact woth maplighian tubules and stomulate rates of primary urine fomation by tubules. Antidiuretic hormones are thought to increase water reabsoption in hindgut.

Question 23

Discuss nitrogen homeostasis in terrestial and aquatic insects.

Answer 23

Terrestrial insects mostly secrete N as uric acid, while aquatic insects mostly excrete N as ammonia. Uric acid is less soluble in water and can be excreted with less water loss. Uric acid is less toxic than ammonia and can be synthesized by fat body and stored in fat body in some insects (storage excretion).