Spider Trachea
The tracheal air tubes permeate throughout the body (or parts of it, depending on species) and open near the tissues, although not in close enough contact to deliver O2 and remove CO2 by themselves as they do in insects. Instead, hemocyanin pigments need to pick up O2 from the air tube ends and deliver it, also passing the CO2 back to the air tube endings. Tubular trachea have a single (rarely two) openings (called a spiracle, or stigma), most often found on ventral side of the abdomen, near the spinnerets. Book lungs Lung or booklung slits (in some species, lung slits come equipped with variable openings that can widen or decrease in size with O2 requirements) open at the anterior portion of the ventral abdomen. A chamber (the atrium) at the opening expands internally leading to the many leaf-like air pockets of the booklung. The booklung is little more than stacked air pockets with an extremely thin cuticle that allows gas exchange by simple diffusion to take place as blood is directed through it. Peg-like structures cover much of the surface of the booklungs on the hemolymph side to prevent collapse. |
There are at least five different respiratory systems in spiders, depending on taxonomic group
and whom you’re talking to. 1) A single pair of booklungs, as with the cellar or daddylongleg spiders, Pholcidae. 2) Two pair of booklungs, suborder Mesothelae, and all or most of infraorder Mygalomorphae (including tarantulas). 3) A pair of booklungs and a pair of tubular trachea, as in the orbweavers and wolf spiders, and probably most species of spiders. 4) A pair of tubular trachea and a pair of sieve trachea (or two pair of tubular trachea if you’re one of those who doesn’t believe the difference between tubular and sieve trachea is enough to distinguish them from each other), as in the small spider family, Caponiidae. 5) One pair of sieve trachea only (or tubular trachea to some), as in the small spider family Symphytognathidae. |