"the creature that's feared above all"
Skeletal & Muscular System
Like insects, tarantulas have a hard cuticle/body shell, known as the exoskeleton. The cuticle covers cephalothorax and legs and prevents the animal from losing moisture and drying out. The cuticle also acts as structural support for the spider. Tarantulas also have an internal skeleton, which serves as surface for muscle attachment. As mentioned earlier, tarantulas do not have antennae like insects do. Instead, they have pedipalps, which act as hands for the spider that easily holds its prey with ease while the digestive fluids and fangs consume the prey. The seven segments of a spider's legs make it much more flexible than human legs, which only have two segments. Like humans, spiders have muscles that bend the legs closer to the body. However, spiders do not have muscles that move the legs away from the body. Each time a spider needs to stretch a leg back out, it must pump a special fluid into that leg. To bend the leg back, pressure is relaxed and the fluid flows out of the leg as the muscles do their work. Many people compare a spider’s leg to a garden hose filling up with water and draining.
The Nervous System
A tarantula's central nervous system is located in the brain. The brain can be found in the bottom of the inner prosoma. A tarantula maintains awareness of its surroundings primarily by using its other sensory organs. Tarantulas have very poor eyesight, so it relies on vibrations, wind direction, and possibly sound received by tiny hairs known as setae located on its legs and abdomen. These tiny hairs play a major role in the tarantula's life because they are used to alert the spider when predators are near, and also detect when a nearby meal is approaching.
The Respiratory System
The Circulatory System
Tarantulas have an, “open blood system”. Tarantulas also have a heart, arteries, and veins to help ensure the haemolymph reaches all of their body. Tarantulas have a slender heart tube that is connected by ligaments to the exoskeleton. Blood pulses out of branching arteries and into the “open body” of the tarantula and then returns to the heart through a series of slits, located along the wall of the heart. The spider’s heart pumps blood through a series of vessels and arteries, but Tarantulas and other spiders lack the complex system that vertebrates have. Tarantulas have a special way of transferring their blood. Their blood seeps between the spider’s tissue, collects in “little pockets” on the underside of the body, and flows back to the spider’s heart. Not all of the spider’s blood passes through the respiratory organs.
Digestive & Excretory System
Tarantulas do not have teeth, instead they use sharp, venomous fangs. Because the Tarantulas do not have teeth, they are unable to chew their food. So, their digestive systems rely on powerful enzymes. After the venom enters the prey, the enzymes of the the tarantula enter the prey’s body and the tarantula must wait for its enzymes to break the food down into a liquid, which the tarantula then can consume. In some cases, the tarantula may need to use its fangs to puncture the exoskeleton around the prey, giving the tarantulas an entry point for injecting its enzymes. The tarantula's stomach is wrapped in strong muscles, which allow it to expand and contract, working like a pump. As the spider consumes more and more, its body expands to accommodate the liquid. After the tarantula consumes its prey, the food is then stored in the caeca, which is a system of sacs and pouches throughout the body that can hold food before it is digested and turned into energy. The tarantula is able to go several days, and sometimes weeks without eating thanks to the usefulness of the caeca. The tarantula is also able to consume prey much larger than itself (mice, lizards, snakes, frogs and, birds). Tarantulas also have an "anal tubercle" through which they expel their waste. Normally their waste takes form of extremely small spheres which is normally found on the most outer part of their burrow.
The Reproductive System
Tarantulas reproduce sexually. Both the testis of males and the ovaries of females are “paired organs” and can be found in the abdomen. The females receive sperm from the males through the “epigastric furrow”, and it is stored in a pair of organs called the “seminal receptacles”. Spiders are unusual in that the males have both primary and secondary sexual organs. The secondary sexual organs are the pedipalps. There is a swollen bulb at the end that can take up, and release sperm into the female’s “epigynum”. This bulb functions like a “pipette, allowing the male to deliver his sperm to the openings of the ducts that lead to the seminal receptacles”.
Sept. 2014. <http://brettmacquarrie.tripod.com/tarantulaanatomy/>.
Tarantula (2011) (HD). youtube.com. N.p., n.d. Web. 23 Sept. 2014.