Subphylum Chelicerata

Characteristics • Six pairs of appendages besides mouth (second pair

are usually pinchers)• The first pair of appendages are the chelicerae

(feeding appendages).• Lack antennae• Lack mandibles (mouthparts)• The body is divided into two distinct regions, the

prosoma (head and thorax) and the opisthosoma (abdomen).

Arachnids

• Have a pair of chelicerate as their foremost appendage-can be pinchers

• Over 85% are spiders or mites

• Palps - a second pair of appendages are used to catch and handle prey.

• The palps are followed by four pairs of walking legs- 8 total

• All Arachnids are carnivores• They have no jaws• They ingest only liquid food- thus

they digest food externally– Usually use enzymes to break down food

source

• Mostly terrestrial

Scorpions

• Large front pincers• Venomous stinger on tail• Holds tail over body as it walks• First animal to successfully invade

land• Fossil scorpions over 425 mya

Scorpions cont…

• nocturnal active at night• Live in tropical warm climates• Only a few are venomous to humans• Young crawl onto mothers back after

born-where they remain for 1 month- if they fall off mother eats them

Spiders

• Have poison glands that secrete toxins through chlicerae that has become fangs

• Use fangs to bite and paralyse prey• Many use webs to trap prey• Some sense prey on web due to

motion• Has eight legs and usually eight eyes

Some Poisonous Spiders

Brown Recluse Black Widow

Mites

• Chiggers and ticks• All the body segments are fused

together• Usually fed on other animals

Mite Example

• Dermatophagoides spp (Bed /Dust Mites) – Bed mites feed on the scales which are

continually falling from our skin.– Dust mites favor homes with high humidity

levels and constant warm temperatures.– Many live in high traffic areas in homes and on

certain furniture items, especially beds, upholstered lounges, chairs, and in carpets with long fibers.

• Nearly 100,000 mites can live in one square yard of carpet.

– Big cause for human allergies

Ticks

Ticks

• Ticks are blood feeding external parasites of mammals, birds, and reptiles throughout the world.

• Important vectors of disease causing agents to humans and animals throughout the world. – Lyme disease is an infection caused by

bacteria which is carried by deer ticks.– Lyme disease to the nervous system can

cause the face to droop

Homework

• What characteristics of arachnids prepare them for terrestrial environment.

• What makes a Chelicerata a Chelicerata?

• Compare ticks and spiders.