Comparative Physiology: Arthropods
Carol Bao, Raymond Cho, and Stephanie Duncombe
Arthropods: Objectives
• Discuss the evolution of arthropods and their breathing
adaptations
• Understand the basic physiology and mechanisms of:
• Tracheae
• Book lungs
• Gills
• Compare and contrast the 3 mechanism of respiration
Arthropods: Evolution
http://www.nature.com/nature/journal/v388/n6643/full/388639a0.html
Arthropods Respiratory Systems
Tracheae
Gills
Book Lungs
Tracheae: Anatomy
Typical of most
terrestrial
arthropods
(i.e., insects)
https://ec-2biol.wikispaces.com/Edens!!!!+page...
http://www.glogster.com/naminejamie/the-respiratory-system/g6kv2kcf60ou06f09v038fa0
Tracheae: Spiracles
• Valve-like openings in exoskeleton
• Located laterally along the thorax and abdomen
http://www.cals.ncsu.edu/course/ent425/tutorial/respire.html#1
Tracheae: Spiracles
• Each spiracle has one or two flap-like valves
• Air flow regulated by small muscles
Wigglesworth V.B. 1972. The Principles of Insect Physiology
http://insectsdiditfirst.com/2013/06/24/going-micro-tubular/
http://cronodon.com/BioTech/insect_respiration.html
Tracheae: Tracheal Trunk
• Main tracheal tubes
http://www.cals.ncsu.edu/course/ent425/tutorial/respire.html#1
Tracheae: Tracheal Tubes
• Subdivisions of tracheal trunk to smaller diameters
• Reach every part of the body
http://www.cals.ncsu.edu/course/ent425/tutorial/respire.html#1
Tracheae: Tracheoles
• Branched extensions that form at tracheae tube
terminals
• Diameters < 1 micrometre
• Terminate within tissues as open-ended or blind-ended
tubes.
Wigglesworth V.B. 1972. The Principles of Insect Physiology
http://www.vasqtec.com/gallery/8
Tracheae: Tracheoles
Insect at rest
tracheole ends filled with fluid
= fluid/gas interface for gas
exchange
= slow O2 exchange
Insect is active
 fluid is removed
= faster O2 exchange
Wigglesworth V.B. 1972. The Principles of Insect Physiology
http://www.vasqtec.com/gallery/8
Tracheae: Fluid Removal
Where does it go?
What causes it?
• Muscle cells or
• Blood stream
Insect is active =
metabolism increases
Anaerobic respiration =
production of metabolites
Oncotic pressure increases
= fluid withdrawal from
tracheole
Wigglesworth V.B. 1972. The Principles of Insect Physiology
Tracheae: Air Movement
Small/inactive insects  diffusion
Large/active insects  diffusion + breathing movements
Wigglesworth V.B. 1972. The Principles of Insect Physiology
https://en.wikipedia.org/wiki/Fairyfly
https://en.wikipedia.org/wiki/Aphid
http://modernfarmer.com/2013/06/bees-good-for-way-more-than-just-honey/
http://www.clickertraining.com/the-butterfly-project
http://www.telegraph.co.uk/news/earth/wildlife/10084659/Fatal-attraction-moths-findmodern-street-lights-irresistible.html
Tracheae: Summary
Insects
Airway Adaptions
Tracheae
Oxygen Transfer
Mediums
Air
-> Tissue
Muscle Control
Passive and Active
Rate of Oxygen
Perfusion
Fast
Chelicerates
Aquatic Arthropods
Book Lungs
• Two pairs in spiders and four in scorpions
https://www.studyblue.com/notes/note/n/finals-flashcards/deck/937667
Book Lungs: Anatomy
• The atrial chamber is located in
an open ventral abdominal cavity
– a small slit (stigmata) connects
it to the exterior. The atrial
chamber is filled with air
• The pulmonary chamber is filled
with lamellae, which are
comprised of 2 layers of cuticle
united at the ends. They contain
hemolymph.
http://askbiology.com/?p=411
Mandal, FB. 2012. Invertebrate Zoology.
Book Lungs: Physiology
• The folds create a
large surface area for
the diffusion of gases
to occur
• Hemolymph enters
one side of the
lamellae and exits the
other
• O2 and CO2 filter into
the tissue via diffusion
http://www.atshq.org/articles/Respiration.pdf
Book Lungs: Respiratory Mechanism
• Dorso-ventricular muscles contract compressing the
chamber, which pushes the air out
• When the muscles are relaxed, the chamber returns to
its original shape and new air flows back in
Mandal, FB. 2012. Invertebrate Zoology.
Book Lungs: Oxygen to the tissue
• Oxygen binds to a respiratory pigment in the
hemolymph (hemocyanin) and is transported
throughout the body
• Oxygen moves into the tissue by diffuse
• Book lungs are slower at supplying oxygen than the
tracheae system, so many active spiders (jumping) use
both book lungs and a tracheae system
http://ednieuw.home.xs4all.nl/Spiders/InfoNed/blood.html
Book Lungs: Summary
Insects
Chelicerates
Airway Adaptions
Tracheae
Book Lungs
Oxygen Transfer
Mediums
Air
-> Tissue
Air
-> Hemolymph
-> Tissue
Muscle Control
Passive and Active
Passive and
Active
Rate of Oxygen
Perfusion
Fast
Medium
Aquatic Arthropods
Aquatic: Adaptations
• Aquatic animals must
acquire a limited supply
of dissolved oxygen from
water.
• Colder water can hold
more oxygen than
warmer water.
• Arthropods that live in
frigid conditions can
remain underwater with
gills while other insects
may need other
adaptations.
Temperature
(Celsius)
Oxygen
(Max. % by
volume)
0
4.9
10
3.8
20
3.1
30
2.6
http://www.cals.ncsu.edu/course/ent425/tutorial/aquatic.html
Aquatic: Adaptations
• Biological Gills
• Plastron Physical Gills
• Temporary air bubbles
• Snorkel-like Breathing Tubes
• Simple thin membrane for O2 Diffusion
Aquatic: Biological Gills
• Water Flow: Cheliped  Gills  Carapace.
• Highly-vascularized gills – O2 transfer from water to blood.
• Highly-folded gills – increase surface area for O2 filtration.
http://aquariumfishs.blogspot.ca/2011/07/fish-structure-and-function.html
Aquatic: Plastron – Physical Gills
• Plastrons – Hydrophobic bristles on aquatic insects that
maintain a thin film of air entire body.
• L-shaped and acts like a “physical gill”.
• Maintains a constant level of oxygen against the spiracles.
websrv.mece.ualberta.ca
Aquatic: Plastron – Physical Gills
• O2 Diffuses into air film from water due to reduced partial
pressure of O2 by respiration.
• CO2 diffuses out of air film due to higher solubility with water.
• Aquatic insects often beat legs or arms to irrigate plastron
region with O2-rich water.
websrv.mece.ualberta.ca
Aquatic: Surface Air Adaptions
Air bubbles
•
•
Some insects have wings,
legs or hairy bodies to
maintain air bubbles.
Maintain air supply for
diving but cannot stay
underwater.
Breathing tubes - Siphons
•
•
Long hollow tubes with a
hydrophobic opening.
Snorkel-like – breathing air
from the surface.
http://www.cals.ncsu.edu/course/ent425/tutorial/aquatic.html
Aquatic: Summary
Insects
Chelicerates
Aquatic Arthropods
Airway Adaptions
Tracheae
Book Lungs
Gills
Hydrophobic Bristles
Oxygen Transfer
Mediums
Air
-> Tissue
Air
-> Hemolymph
-> Tissue
Water -> Blood
Or
Water -> Air -> Blood
Muscle Control
Passive and Active
Passive and
Active
Passive and Active
Rate of Oxygen
Perfusion
Fast
Medium
Slow