Knowra Spider anatomy Spider anatomy Spider anatomy is the body organization of spiders: a cephalothorax joined to an abdomen by a narrow pedicel, four pairs of legs, and specialized mouthparts and silk-producing organs.
Cephalothorax : The fused head and thorax of a spider, bearing its eyes, mouthparts, legs, and pedipalps. This front body region carries the spider’s locomotor and feeding appendages.
Spider locomotion : The ways spiders move using coordinated leg muscles, hydraulic pressure, and, in some species, silk-assisted travel. Leg joints and internal pressure explain how the body produces walking and jumping.
Spider eye : A simple visual organ with a lens and retina; most spiders have several pairs arranged on the cephalothorax. Eye placement and structure vary with hunting style and visual demands.
Arachnid : A chelicerate arthropod in a group that includes spiders, scorpions, mites, and harvestmen. Spiders share their basic body plan with a much broader group of joint-legged animals.
Opisthosoma : The posterior body region of a spider, containing most digestive, reproductive, respiratory, and silk-producing organs. This abdomen houses many organs absent from the cephalothorax.
Hydraulic extension in spiders : A mechanism in which hemolymph pressure extends some spider leg joints because those joints lack opposing extensor muscles. Internal fluid pressure helps extend the legs during movement.
Spider venom : A mixture of bioactive substances produced in venom glands and delivered through fangs by many spiders. Glands connected to the chelicerae make biting anatomy an effective prey-capture system.
Insect anatomy : The body organization of insects, typically divided into head, thorax, and abdomen, with six legs and antennae. Insects have three main body regions and six legs, unlike spiders’ two regions and eight legs.
Pedicel : The narrow stalk connecting a spider’s cephalothorax and abdomen. Its flexible connection lets the two major body regions move relative to each other.
Book lung : A spider respiratory organ composed of stacked, thin-walled plates that exchange gases with the hemolymph. Some spiders breathe through paired plate-like organs inside the abdomen.
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