.
ANATOMY

This multicolored rendering of Theraphosa blondi, a South American bird-eating spider, reveals the complexity of this arachnid's anatomy. Learn about the tarantula's organs by clicking on the color key at left.







.

Book lungs
Air moves through the tarantula's four book lungs where oxygen diffuses into the bloodstream. Stacked side by side are alternating spaces of air and blood, which resemble the leaves of a book, hence the apt name of book lung.











.

Heart
The slender heart tube 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, or ostia, located along the wall of the heart.











.

Nervous System
Located in the head, two compact clusters of nerve ganglia form the tarantula's central nervous system. Nerves radiate from this control center to the rest of the tarantula.











.

Digestive tract
To process their liquid meals, tarantulas have developed an extensive digestive tract consisting of an esophagus, sucking stomach, midgut, and excretory organs. Such an efficient system permits the tarantula to go for over a month without eating.










.

Eggs
The tarantula's abdomen swells with eggs just prior to their release into a cocoon. Packed with energy, the egg cell's yolk contains all the energy needed for the embryo to develop into a juvenile tarantula.











.

Silk glands
At least three different silk glands reside within the tarantula's abdomen. While inside the glands, the silk is liquid. The transformation to a solid thread results from tension when the silk is excreted through spinnerets.