Lecture 7 - Insect Respiration and Circulation Flashcards
Respiratory System of Insect
(3)
The respiratory system of an insect consists of spiracles and trachea that are connected
(A) The spiracles are present on the external surface of the insect
(B) The trachea are present on the internal surface of the insect
Circulatory System of Insect
(3)
The circulatory system of an insect consists of dorsal blood vessel
These dorsal blood vessel is made up of of multi-chambered heart and aorta (Muscular tube)
The aorta is present on the thorax of the insect and it goes toward the head of the insect
Background information: Respiratory Systems of Insects
(2)
Air will enter through their spiracles which are holes in the abdomen and thorax of insect
Air enters the spiracle to travel through a network of tubes known as the trachea to reach the cells in the insect body
2 main components of the respiratory system
a. Spiracles
b. Trachea
Spiracles
(5)
These are external opening on the external surface of the insect
There are ONLY one pair of spiracles per segment
Usually these spiracles occur on the mesothorax, metathorax and the abdominal segments (1-8)
There are no spiracles on the head, prothorax, and genital segments
The spiracles are connected to the longitudinal tubes known as the tracheoles
Trachea
(2) +EG
These are series of air-filled tube that are unique to insects
These trachea are lined with cuticle and are extensively branched (Eg. 39% of body volume of the June Beetles)
Components of Insect Trachea
(3)
a. Tracheal Trucks
b. Taenidia
c. Tracheoles
Tracheal trunks
Longitudinal Truck
Taenidia
Spiral cuticular thickening that line ONLY the trachea, w/o the taenidia the trachea would collapse
Tracheoles
(2)
- These are the smallest diameter tubes ( < 1 micron in diameter that extend b/t the muscles)
- Deliver oxygen to all cells of the body, and each tracheoles end blindly
Trachea in Silkworm larva
Each spiracle consists of 103,000 tracheoles with a combination of 1.5 million together
What happens when an insect is a rest in a respiratory system?
(3)
- When an insect is at rest, there are fluids known as resting tissue at the tips of the tracheoles
- O2 will enter the tissue, and the purpose of the fluid at the resting tissue is to assist in gas exchange
- When the insect is active, there is a change in fluid, as it moves into the cell of the insect to provide more space for gas exchange (this allows for more O2 exchange and CO2 moving out)
Passive Diffusion in Small Insects
(4)
Passive diffusion occurs in small and non active insects
O2 moves by passive diffusion in insect by the spiracles
The spiracles are the major source that is used to prevent dessication (water loss) as the spiracles are usually only ½ to ⅓ open
This allows for continuous O2 uptake and CO2 storage which causes suction
CO2 expel in Small insect
(3)
CO2 is stored in the hemolymph as bicarbonate and is expelled by the cyclical bursts
The cyclical bursts creates a negative pressure that is sucked into the trachea
When the concentration of the CO2 in the trachea is greater than 6.5%, this causes the spiracles to relax and CO2 is expelled
Example of Cyclical Bursts interval in other insects
(2)
(A) Every 20 mins it is expelled in the termites
(B) Every 6hr it is expelled in the moth pupae
How do insects prevent water loss?
(2)
Spiracles are ⅓ open
Cyclical bursts
Steps of Active Diffusion in Large Insects
(4)
Large insects would need to use active transport as they move air into and out of the tracheal system
This is done by opening the forward spiracles (meso and metathorax spiracles) and the rear segment (abdominal segment)
Insect close forward spiracles and forces air out of the rear spiracles by increasing their blood pressure and muscle contraction
Insects close spiracles in the rear segment which creates a negative pressure to allow for air to come into the forward spiracles
Tracheal Air Sac (Flying Insects): Large Insect
(4)
These tracheal air sacs are found in large insects particularly flying insects
When the trachea is dilated, it stores air into the air sac, and when oxygen is high in demand the tracheal air sac acts as a balloon to move air in and out of the body, this allows for increase in tidal flow
The tracheal air sac is flexible in which it can provide room for the egg development
During flight, the locusts have separate ventilation in the pterothorax
Arrangemenet of Spiracles
(5)
a. Holopneustic
b. Metapneustic
c. Propneustic
d. Apneustic
e. Atracheate
Holopneustic
All the spiracles are functional meaning that are spiracles on the mesothorax, metathorax, and abdominal segment 1-8
Metapneustic
Eg
The spiracles are ONLY on the abdominal and ONLY abdominal segment 9 is functional
Eg: Mosquito Larvae
Propneustic
Eg
Spiracles are ONLY present on the prothoracic and are functional
Eg. Mosquito Pupae
Apneustic
(3)
There are no functional spiracles instead there are abdominal tracheal gills
These gills are found in mayfly, damselfly, stonefly (naiad)
The gills are modified hindgut in dragon naiad
Atracheate
Eg
These insects don’t have trachea therefore would use atracheate (gas exchange take place through the integument)
Eg: Collembola (Springtails) and some hymenopterous larvae
Siphons
Are found in aquatic insects where O2 is taken in by these siphons (in the abdomen) found in Giant Water bug and Water Scorpions
Diving Beetles
(2)
O2 is taken in by trapping it as an air bubble b/t the elytra and the abdominal terga
These air bubbles are replaced every 30 mins
Waterboatmen
(2)
These are hairs on the abdomen that consists of continuous air bubble in place
It has abdomen silvery appearance
Additional Function of the Tracheal System
(7) + Description
Suspend internal organs
Air pressure needed for ecdysis
Thermoregulation - there are insulation layer in the flight muscle
Pathway for development of nervous system
Weight reduction (Hollow structures)
Sound perception (Tympanum is a modified spiracles used for sound perception)
Defense (Eg. Spittlebug froth, defensive secretion from some grasshoppers and moths)
Insect have an “Open” Circulatory system, it consists of 2 components
Hemocoel (body cavity)
Hemolymph (blood) that bathes the organs
Organization of the Circulatory system
(4)
Blood always flow from posterior end of the body to the anterior end of the body
Circulatory organs include the multi chambered “heart” and the “aorta”
Each chamber has a pair of ostia (valves) which allows blood to flow into the heart
BUT not in the opposite direction (unidirectional!)
Peristalsis contraction from the heart forces the blood from chamber to chamber
Types of chambers in insects
(2)
There are 13 chambers in the cockroaches whereas there are 3 chambers in the housefly
2 Diaphragm of the Circulatory System
Dorsal Diaphragm
Ventral Diaphragm
Dorsal Diaphragm
Consists of the pericardial sinus where the heart sits
Ventral Diaphragm
Consists of the perineural sinus
3 body cavities
Pericardial Sinus
Perineural Sinus
Perivisceral Sinus
Pericardial sinus
(2)
Contains the heart of the insect
Present on the dorsal diaphragm and the dorsal body wall
Perineural Sinus (2)
Contains the ventral nerve cord of insect
Present on the ventral diaphragm and the ventral body wall
Perivisceral Sinus (2)
Contains the alimentary canal (gut)
Present on the ventral diaphragm and the ventral body wall
Local Pulsating organs
These local pulsaitng organs pushes the blood into the base of the wings, legs, and antennae
Composition of Insect Hemolymph
(4)
Insect blood is a colorless liquid that consists of 84-92% H20
It contains high concentration of amino acid, inorganic ions, proteins, sugar
It consists of a pH of between 6-7
It makes up 15-30% of the total body weight and 15-70% of the body volume
Cells in the Hemolymph of Insects
Insect consists of >9 cells but the two main cells are:
Hemocytes
Plasmatocytes (Types of Hemocytes)
Plasmatocytes (2)
The function is phagocytic on bacteria and other foreign microorganisms
It can encapsulate parasitoid eggs
Functions of Hemolymph
(7) + Description
Transport nutrients, waste and hormones, Hemolymph does not carry o2
Act as a water storage
Lubrication of internal organs
Heat exchange (wings act as solar collectors)
Hydraulics (molting, wing expansion, active ventilation, leg / antennal movement)
Protection from microorganisms, parasites
Defense (reflex bleeding)
