EXAM #2

Question 1

What are the components of the circulatory system? How does it work in insects?

Answer 1

Hemolymph (insect body fluid) and longitudinal dorsal vessel (heart). In insects, the circulatory system is open (hemolynph not in vessels). Hemocoel is the body cavity in which hemolymph resides. Dorsal vessel is a pulsatile structure that extends the length of thorax and abdomen.

Question 2

What are the functions of the corculatory system?

Answer 2

Cold protection and thermoregulation;
Hydrostatic movement; 
Hemolymph coagulation (wound healing);
Immunity;
Buffering of CO2;
Transport of nutrients, hormones, and waste;

Question 3

Hemolynph constitution and chemical composition.

Answer 3

20-40% in soft body larvae;
<20% in adults;
85-90% solids / 10-15% water
Major ions: Na, K, Ca, Cl, PO4, amino acids.
Proteins: storage proteins, lipophorins, vitellogenin, etc);
Trehalose (the principal sugar);
Neuropeptides and hormones;
Uric acid;

Question 4

Discuss the circulation of hemolymph.

Answer 4

Dorsal vessel is a simple tube divded into “heart” and “aorta”. Closed posteriorly, opened anteriorly. Heart is the abdominal portion and includes alary muscles (support vessel) and ostia. Aorta is the thoracic portion, Ostia are paired openings in which hemolymph enters/exits.

Question 5

Discuss the heartbeat.

Answer 5

Originates posteriorly and travels anteriorly. 15-100 beats per minute. Myogenic contraction (originates in muscle itself).

Question 6

Describe the hemolymph flow.

Answer 6

Flows through dorsal vessel from posterior to anterior, causing a flow in hemocoel from anterior to posterior (flow may periodically reverse).

Question 7

Types of hemocytes and function?

Answer 7

Prohemocytes = may become other types
Plasmatocytes = phagocytosis and encapsulation
Granulocytes = storage and secretion?
Coagulocytes = coagualtion of plasma to heal wounds

Question 8

Roles of the insect fat body?

Answer 8

Storage of carbohydrates, fat, and protein;
Synthesis and regulation of blood sugar;
Synthesis of hemolymph proteins;
Metabolism of carbohydrates, lipids, and nitrogenous compounds;
Uric acid synthesis -

Question 9

Main roles of the respiratory system?

Answer 9

Gas exchange: to obtain and deliver oxygen, to eliminate carbon dioxide.
Respiration: Tracheal systems - network of tubes that “branch and ramify” througout the body. Smalest branches (tracheoles) deliver oxygen to all organs and tissues.

Question 10

What are spiracles? Where are spiracles located in insects?

Answer 10

Spiracles are openings through air enters tracheae in terrestrial insects. Located laterally. Most spiracles have a chamber (atrium) and a valve. It can be opened and closed for water conservation.

Question 11

Why is gas exchange considered to be discontinuous in insects?

Answer 11

Gas exchange occurs into three distinct stages. First, spiracles are closed (C) and then fluterring happens controled by levels of oxygen (F). Finally, levels of CO2 and HCO3 in hemolymph control the opening of spireacles (O).

Question 12

How is oxygen delivered to cells?

Answer 12

Oxygen enters through spiracles and passes tgrough tacheae then tracheoles into target cells by difusion. Oxygen in, carnbon dioxide out. Active movement of thorax and/or abdomen works as vnetilation. (Tracheal system may limit size of insects because it relies heavily on difusion).

Question 13

Discuss the respiratory system adapatations in aquatic insects.

Answer 13

Tracheal systems structurally similar to terrestrial insects. Water prevented from flooding tracheae by hydrophobicity and closing of spiracles (many must come to surface to breathe). Compressible gas gills bubble on body and imcompressible gas gills continually obtains oxygen from water. Some insect access air filled spaces in plants.

Question 14

Discuss cutaneous respiration in aquatic insects.

Answer 14

Via tracheal gills. Thin cuticle plus extensive tracheal network near cuticle allows absorption of oxygen.