Book lung
The book lung , fan lung or fan trachea is one of the respiratory organs of spiders and scorpions next to the tubular trachea and the skin .
description
The book lungs are always on the front ventral side ("belly side") of the opisthosoma (abdomen), in pairs on the left and right of the body center line. The breathing openings ( stigmata ) are slits that are formed by the rear edge of the hairless lungs. The lungs can be moved by muscle contraction and increase the stigma. The stigmata extend into the interior of the body and there form the respiratory atrium formed from a thin cuticle layer. From the respiratory vestibule, invaginations delimited by a cuticle, the respiratory pockets, extend horizontally into a cavity filled with hemolymph , the pulmonary sinus. The breathing bags are prevented from collapsing by cuticle columns. Because of the structure of the superimposed breathing pockets, one speaks of book lung or fan lung . The cuticle layer is formed from the hypodermic lamellae .
functionality
Almost all of the hemolymph has to pass through the book lung on its way back to the heart . The hemolymph flows from the prosoma (front body) through two lateral cavities (lacunae) in the petiolus into the pulmonary sinus in the foremost part of the opisthosoma. Lacunae from the posterior area of the opisthosoma also flow into the pulmonary sinus. From the pulmonary sinus in the middle of the body, the hemolymph flows sideways between the breathing pockets. Oxygen diffuses through the thin cuticle and hypodermic lamellae . The oxygenated hemolymph flows up the sides through another ascending pulmonary sinus to the heart. There is probably no ventilation , apparently the diffusion is sufficient for the uptake of oxygen.
Development history
The tubular trachea presumably developed from the fan trachea. The latter are often found in smaller spiders. The "primitive" articulated spiders , tarantulas and Hypochilidae have two pairs of book lungs in the second and third abdominal segment. In most real spiders , the second pair is converted to tube trachea. The fan tails are the same in all weaving spiders; the tube tracheas, on the other hand, are diverse and diversified. Given the variety of spiders, it is difficult to say whether the book lung or the tube trachea play the more important role. In the water spider, for example, the book lungs are smaller, in the Caponiidae both pairs appear as sieve or tube tracheas, trembling spiders (Pholcidae) have only one pair of book lungs, Symphytognathidae only have one pair of sieve tracheas.
swell
- Rainer F. Foelix: Biology of the spiders. Georg Thieme, Stuttgart 1979, ISBN 3-13-575801-X .