Spinneret
Spinnerets are the Ausführorgane of spiders for her in the silk glands synthesized spider silk . The extremely mobile, mostly multi-limbed appendages in the fourth and fifth abdomen segment were originally present in four pairs, but in the more recent species they are arranged in three or two pairs each. The spinning bobbins, the actual excretory organs for the silk, sit on movable plates at the tips.
Like the extremities, the spinnerets are mainly moved by the flexor muscles, while the stretching is done by the hemolymph pressure . The muscles attach to the joint membranes and pull through the entire spinneret to move the spinning bobbin. This allows the spinnerets to be unfolded, rotating movements for the attachment points of a thread, and being moved up and down. The abdomen is also mobile, which increases the radius of action of the spinnerets.
The spinning bobbins can be compared with cannulas, the opening of which is only a fraction of a millimeter in diameter. They can be divided into different types that perform different functions, e.g. B. glue secretion, scaffolding threads, signal threads, catch threads, cocoons, etc., which are assigned to the different spinnerets. Several different types of spinning bobbins can sit on a spinneret. Cribellate spiders have three pairs of spinnerets, the fourth pair is converted to the cribellum. The cribellum of some cribellate trapping wool weavers can carry up to 20,000 spinning bobbins, the openings of which are only 10 nm (1 / 100,000 mm ) in diameter. In Leimfadenweber to three pairs of spinnerets and the fourth pair is converted to Colulus. Glue thread weavers can have up to six spinnerets.
Spinnerets are transformed extremities of the 4th and 5th segments of the opisthosoma. Four pairs of spinnerets are only present in the articulated spiders .
source
- Rainer F. Foelix: Biology of the spiders. Georg Thieme Verlag, Stuttgart 1979, ISBN 3-13-575801-X .