Arthropods Flashcards
How do arthropods maintain their water balance?
Behaviorally: they occupy moist microclimates, change activity patterns, select moisture-rich food and drinks.
Anatomically: they have an impermeable physical barrier.
Physiologically: Arthropods have kidney related structures that are tubular and acts as an initial collecting area where the formation of the primary urine takes place as well as having one or more areas where urine can be modified which eliminates unwanted substances and retains or reabsorbs needful constituents.
Book lungs
Present in arachnids.
It is the invagination of opisthosoma limb buds (thin chitinous cuticle). Has leaf like lamellae in an air-filled cavity (atrium). Opens via the use of spiracles.
Spiracles
Openings on some animals which usually lead to the respiratory system.
Opisthosoma
The posterior part of the body in some arthropods, situated behind the prosoma.
Lamellae
Numerous plate or disc like structures at both a tissue and cellular level.
Scorpion gas exchange
Has only four pairs of book lungs.
Spiders gas exchange
One or two pairs of book lungs and tracheae can both be present.
Arthropods Gas exchange
Uses passive ventilation.
The hemolymph flows through the lamellae. Air flows in through the spiracles and travels through the spaces shaped like struts/spines, which is how the hemolymph becomes oxygenated.
Tracheal system in arthropods
Present mostly in insects. It is internal and are air-filled tubes. The tracheal system branches out through the body, from tracheae to tracheoles. It sometimes opens via spiracles. It contacts internal organs/tissues directly. The more active the organism, the more extensive the tracheal system.
In large insects there is a main trachea.
Other arthropods with tracheal systems
Myriapoda
Arachnids
Onychophora
Oniscoidea (crustaceans)
Tracheal system process
Oxygen is delivered directly to the cells. Oxygen from the air travels from the spiracle to the tracheae then the tracheoles. From there it dissolves into the moist tracheole surface and finally diffuses into the cells.
CO2 and water diffuses out out the cells into the moist tracheal surface, from there it goes to the tracheoles then the tracheae. From the tracheae it travels out of the body through the spiracles.
The circulatory system is not involved with gas transport.
Active ventilation
Occurs in larger insects with air sacs.
Allows insect to open some spiracles while closing others. The abdominal muscles are able to expand or contract the body’s volume.
Insect size
Limited by the rate of gas diffusion and the weight of exoskeleton.
Open tracheal system
Has spiracles.
Present in terrestrial insects and in some aquatic insects. Some have ventilated air sacs (honey bees).
Closed tracheal system
Oxygen diffuses through sealed spiracles. Present in many endoparasitic larvae.
Present in the form of tracheal gills in some aquatic stages.
