Chelicerae
As chelicerae or jaws claw the characterizing feature of the maxillary jaw carrier ( Chelicerata ) is called. It is a converted into a mouth tool extremity in the head region, which is located in front of the mouth opening.
Structure, and system
The chelicerae is primarily three separate levels with scissors ( Chela ) provided. It is supplied from the third part of the brain ( Tritocerebrum ) with nerves and is correspondingly homologous with the second antennae of crayfish. In embryonic development, the chelicerae are created behind the mouth and then move later to the front.
Within the Chelicerata the chelicerae and the subsequent limb is modified ( Pedipalpus at the arachnids ) in many ways. Thus we find the tripartite scissors still in the sea spiders, horseshoe crabs, scorpions, mites and Palpenläufern.
In the summarized as Megoperculata scourge scorpions, whip spiders and spiders the chelicerae consists of only two members, the second member against the first is einschlagbar (pseudo Chela ). It is also provided in the spiders with a large poison gland, which can far into the front body of the spider ( prosoma ) rich. Spiders in the original, such as the bird arachnids which Cheliceren directed forward, the jaws are folded parallel to the bottom. This state is referred to as orthognathic. For more advanced spiders ( Araneae True, Araneomorphae ) the chelicerae are placed vertically and at the same time turned inwards. In this way, they can be like pliers open at the base and work against each other. It involves the labidognathen state.
The summarized as Haplocnemata pseudo scorpions and spiders and rolling the hood spiders possess a two-tier chelicerae, but forms a true scissors here. The pseudoscorpions the chelicerae is also connected to the outputs of silk glands and cleaning combs ( Serrulae: serrula exterior and interior serrula ) equipped.
Inward-pointing chelicerae ( labidognathen ) of the nurses mandrel finger ( Cheiracanthium punctorium ), a genuine Spiders. At the ends of the jaws occurs from poison.