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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)
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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 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.