Spiracle
From Wikipedia, the free encyclopedia
Spiracles are small openings on the surface of animals that usually lead to respiratory systems.
In elasmobranchs (sharks, skates, and rays), a spiracle is found behind each eye, and is often used to pump water through the gills while the animal is at rest (Fouts, 2003). A spiracle is also found in primitive bony fishes as the bichir.
In insects and some more advanced spiders, spiracles allow air to enter trachea (Solomon et.al., 2002). However, the two groups differ in how the tracheae function; in insects, the tracheal tubes primarily deliver oxygen directly to the animals' tissues. In spiders, however, the oxygen diffuses into the hemolymph (Foelix, 1996). A similar diffusion effect also occurs in some insect caterpillars. In these latter groups, then, the respiration is more reminiscent of lungs (in spiders and other arachnids, they have structures called book lungs, in fact).
[edit] References
- Fouts, William. April 2003. Marine Science Dept. Orange Coast College.
- Solomon, Eldra, Linda Berg, Diana Martin. 2002. Biology. Brooks/Cole.
- Foelix, Ranier. 1996. Biology of Spiders. Oxford U. Press
