Collections II: Entomology Respiration & Circulation

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.

Tracheal System of a Cockroach

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

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

Spiracles trachea

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

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

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

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)

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