Chelicerates

Pronunciation

How to pronounce Chelicerata: //kɛˌlaɪsəˈreɪtə//

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Summary

Chelicerata, a subphylum of arthropods, includes diverse organisms such as spiders, scorpions, and horseshoe crabs. They are characterized by their unique body structure, feeding methods, and ecological roles. Their evolutionary history dates back to the Cambrian period, highlighting their ancient origins and adaptability.

Physical Characteristics

Chelicerates have segmented bodies with jointed limbs, covered in a tough cuticle made of chitin and proteins. Their body plan consists of two tagmata: the prosoma (cephalothorax) and the opisthosoma (abdomen), although in mites, this division is not visible. They possess specialized appendages called chelicerae, which are used for feeding, and pedipalps, serving various functions depending on the group. Most have either gills (marine) or book lungs and tracheae (terrestrial).

Identification Tips

Chelicerates are identified by their two main body segments (prosoma and opisthosoma), presence of chelicerae, and lack of antennae. Their body plan and appendages vary widely across different groups (e.g., spiders have fangs, scorpions have pincers).

Habitat

Chelicerates inhabit a variety of environments, including marine, terrestrial, and some freshwater habitats. They can be found in diverse ecosystems, from oceans to deserts and forests.

Distribution

Chelicerates have a global distribution. Marine species such as horseshoe crabs and sea spiders are found in oceans worldwide, while arachnids like spiders and scorpions are prevalent on land in numerous biomes.

Diet

Chelicerates display a variety of feeding strategies including predation, parasitism, herbivory, scavenging, and detritivory. Most modern chelicerates are liquid feeders, using digestive enzymes to liquefy their prey.

Life Cycle

Chelicerates exhibit varied reproductive strategies. Marine chelicerates, like horseshoe crabs, utilize external fertilization, while most arachnids (land dwellers) employ internal fertilization. Young often hatch resembling small adults but some species provide parental care.

Reproduction

Reproduction varies between groups; horseshoe crabs spawn on sandy beaches while most arachnids use internal fertilization with many undergoing courtship rituals. Some species are viviparous, such as certain scorpions, which give birth to live young.

Predators

Many chelicerates, particularly arachnids such as spiders and scorpions, have few natural predators due to their venomous defenses, though larger animals, birds, and some reptiles may prey on them.

Ecosystem Role

Chelicerates play significant roles in ecosystems as predators, herbivores, and scavengers. They help regulate populations of other species and contribute to nutrient cycling in ecosystems.

Economic Impact

Chelicerates can have both positive and negative economic impacts. While some spider venoms are being researched for medicinal applications, others like ticks and mites are agricultural pests and health hazards.

Cultural Significance

Some species of chelicerates, such as tarantulas, are considered delicacies in various cultures. Horseshoe crab blood is significant in the medical field, and some spiders are utilized in traditional medicine.

Health Concerns

Certain chelicerates can pose health risks; for instance, ticks transmit diseases like Lyme disease, whereas spider and scorpion bites can be fatal in specific cases.

Collecting Methods

• Hand collection
• Pitfall traps
• Web sampling

Preservation Methods

• Ethanol preservation
• Drying specimens
• Freezing

Evolution

Chelicerates are believed to have diverged from Mandibulata in the mid-Cambrian period, with characteristics that distinguish them from other arthropod groups. They exhibit diverse evolutionary adaptations and relationships.

Similar Taxa

• Mandibulata
• Arachnida
• Xiphosura
• Eurypterida

Misconceptions

There is often confusion about the classification of sea spiders as chelicerates due to their distinct morphology and ecological roles. Additionally, spiders and scorpions are commonly feared, leading to misconceptions about their risk to humans.

Tags

• arachnids
• horseshoe crabs
• evolution
• biodiversity
• ecology