To exchange for oxygen in water.
Aquatic arthropods mostly exchange gases through (c) gills; some (like the horseshoe crabs) have book gills. The "book lungs" term usually applies to most arachnids like scorpions and spiders, which are terrestrial; most other terrestrial arthropods exchange gases through special holes in their segments called spiracles, attached to the tracheal tubules/tracheola which connect directly to the tissues.
gills
The gills of a mushroom house the basidia, the cells on which the spores are produced. The gills function as a large surface area over which to produce millions of spores that is exposed air yet protected from large fluctuations in air temperature, moisture, etc.
The Gills
in their gills.
gills
Gills
In prawns, gas exchange occurs through specialized gill structures. These gills are rich in blood vessels and allow for the exchange of oxygen and carbon dioxide between the prawn's respiratory system and the surrounding water. The thin, permeable surface of the gills facilitates efficient gas exchange.
Crayfish exchange gases through gills located underneath their carapace. Water is drawn in through the crayfish's openings and passes over the gills, where oxygen is absorbed and carbon dioxide is released.
Across the alveoli and capillaries.
Carbon Dioxide