Tarantulas Eddie D. Williams
July 25, 2011
Tarantulas, or more specifically Grammostola pulchras or G. pulchras are amazing organisms. Tarantulas are equipped with many important organs that ensure their survival in their environment. One important organ is the silk gland. Silk glands produce silk. Another important organ in a tarantula is the spinnerets. Spinnerets are very important for survival, and here sticky fluid is released that dries into silk. The venom glands are also very important and are used for defense and catching prey. The book lungs in a tarantula are responsible for oxygen. Without these organs, tarantulas would not be able to survive. ...view middle of the document...
In the lowest parts of the tarantulaâ€™s limbs are excretory glands that secrete and excrete body fluids, which are considered waste. â€œThe silk glands may represent modified glands that now produce silk instead of waste products, just as the spinnerets represent highly modified limbsâ€ (Australian Museum, 2009, para. 38). It is possible that an intermediate stage in this process could be the production of a secretion, which includes a scent released by the tarantula as a signal to assist the tarantula in finding the way back to its retreat burrow. The silk becomes useful to the tarantula as a safety line to capture its prey, produce egg sacs, and many other activities. These tasks will not be possible if the spinnerets were not available.
Tarantulas have poison or venom glands in their chelicerae, or jaws. The chelicerae contain both the fangs and the venom glands. The chelicerae are used to inject venom through their fangs into the prey. The fangs are hollow extensions of the chelicerae and are so sophisticated that they can extend outward and downward in preparation to bite. They can also fold back toward the chelicerae just like a pocket knife blade folds back into its handle (White, 2006). Venom serves two primary roles, which are to capture prey and defend the organism from prey. Years ago venom was primarily used for capturing prey but has evolved and is now used for defense as well.
Tarantulas use their venom glands to overpower their prey. The venom contains a combination of digestive secretions and a paralyzing agent. Tarantulas typically will only eat live food, which is why their venom glands are so important. After a tarantula catches and paralyzes its prey, the prey is injected with strong digestive enzymes that liquefy the contents of the insect (Willis, 1999). The venom in tarantulas is so powerful that the tarantulas can take down animals as large as lizards.
Spiders have either book lungs or tubular tracheae or both. Tarantulas have four book lungs. â€œBook lungs are located by two hairless patches on the underside of the spider's abdomen. Each lung has an open slit for air intact and a stack of leafletlike, blood filled structures called lamellae. As air passes into the spider's body, blood passes through the lamellae is oxygenatedâ€ (MacQuarrie, 2006, para. 14). The book lungs are designed to contain side-by-side spaces of air and blood to facilitate diffusion of oxygen into the bloodstream. The folded nature of the book lung prepares for maximum exposure to air and consequently facilitates optimal gas exchange between the blood and the environment.[pic]