1. Collections II: Entomology
Respiration
&
Circulation

2. Insect Respiration Overview:
Waterproof cuticle = permeable to water and oxygen by diffusion
System of internal branching tubes (trachea):
Very fine branches (tracheoles) penetrate individual cells
Trachae have spiral stiffening - like vacuum cleaner hose - to prevent collapse.

3. Tracheal System of a Cockroach

4. Oxygen Pathway:
Air enters from the outside through a series of openings (spiracles)
Typically 2 pair of spiracles on the thorax and 8 pair on the abdomen
Pathway of oxygen =
O2 from spiracles --> tracheae --> tracheoles > cells

5. Water loss and additional respiratory structures:
To avoid water loss through spiracles:
opening and closing devices
filtering lobes or hairs before trachea
Active insects:
Internal air sacs  extra reservoirs
Mechanical ventilation (using specialized valves) along the larger trachae
Bees and wasps extend their abdomens to pump air across

6. Spiracles
trachea

7. Insects could have one or more to aid in aquatic respiration:
tubes
connecting to the air at the water surface
hydrofuge hairs (water resistant)
associated with the spiracles to keep water out
tracheal gills
whereby oxygen diffuses from the water to fine surface trachae.
bubble of air
hemoglobin
Directly diffuse oxygen across their cuticle.
spiracles at the end of siphons 
open into the trachae/penetrate the skin of their host

8. The Circulatory System Overview:
Open circulatory system = blood (haemolymph) flows freely through the body cavity (haemocoel)
There is a dorsal vessel = closed at the end of the abdomen and opens in the head (aorta).
several chambers
valve-like openings (ostia)
pumped forward to the aorta and into the body cavity

10. Blood Overview: Blood contains: Water - about 90%
Inorganic ions - dissolved salts of Na, K, Ca, Mg.
organic molecules - amino acids, sugars for muscle use
Blood cells
does not generally contain hemoglobin

11. Function of Blood: Lubricant
Hydraulic medium - can transfer forces to different parts of the body
Transport - sugars, fats, proteins, wastes, hormones
Protection (blood cells)
Defense (rare)

12. Rate of Blood Flow:
helped by general muscular contractions and movement
pumping muscles on either side of the dorsal vessel
in active insects, additional pumping organs at the bases of the wings legs and antennae
The pulse rate is controlled by hormones and varies with temperature/activity
The open circulatory system is inefficient
Injected Dye  5 minutes to permeate the insect…less than 1 minute in humans