Chelicerae

Chelicerae

Diagram of chelicerae in a spider

The chelicerae are a pair of appendages found in arachnids, including spiders, scorpions, and harvestmen. They are located in front of the mouth and are used for feeding, defense, and manipulating prey. The word "chelicerae" is derived from the Greek words "chēlē" meaning "claw" and "keras" meaning "horn."

Anatomy

The chelicerae consist of two segments: the basal segment, known as the "scape," and the terminal segment, known as the "fang." The scape is attached to the cephalothorax, which is the fused head and thorax region of the arachnid. The fang is movable and contains a venom gland, which is used to inject venom into prey or enemies.

Function

The primary function of the chelicerae is feeding. Arachnids use their chelicerae to grasp and immobilize their prey. The fangs are then used to pierce the prey's exoskeleton and inject venom, which helps in digestion and subduing the prey. The chelicerae also play a role in defense, as some arachnids can deliver painful bites to deter predators or humans.

Evolution

The evolution of chelicerae is believed to have occurred in the early ancestors of arachnids. Fossil evidence suggests that the chelicerae evolved from modified appendages that were originally used for feeding in primitive arthropods. Over time, these appendages became specialized for capturing and manipulating prey.

Diversity

Chelicerae exhibit a wide range of diversity among different groups of arachnids. For example, spiders have chelicerae that are equipped with fangs capable of injecting venom, while scorpions have chelicerae that are modified into pincers. Harvestmen, on the other hand, have chelicerae that are used for grasping and manipulating food.

Importance

The chelicerae are crucial for the survival and success of arachnids. They enable arachnids to capture and consume a variety of prey, which contributes to their role in maintaining ecological balance. Additionally, the venom delivered through the chelicerae plays a vital role in subduing prey and defending against predators.

See Also

• Arachnids
• Spider anatomy
• Scorpion anatomy