Phylum Arthropoda insects, spiders, scorpions, ticks, mites, centipedes, millipedes, and crustaceans largest phylum in the animal kingdom; one million species recorded; est. > 30,000,000 mostly small; active (complex behaviors) ecologically diverse & economically important

Positive Impacts food for humans pollinators decomposers silk, wax, honey predators & prey- integral part of the food web bioindicators biological control

Negative Impacts competitors pests disease vectors parasites venomous

General Features eucoelomate, protostomes exoskeleton - support; protective water loss, mechanical injury, chemical injury, & UV barrier made of chitin- polysaccharide similar to cellulose; strong & indigestible protein, lipid, & CaCO3; water and gas impermeable ecdysis - molting/shedding

Exoskeleton epicuticle procuticle sclerotization resilin

Metamerism conspicuous segmentation repetition of tissues & organs

Tagmatization segments fuse together into body parts: head cephalothorax thorax abdomen

Arthropod Features (cont.) jointed appendages: (specialization) locomotion, sensation, & feeding generally one pair/segment complex muscular system complete & complex digestive system

Circulation & Respiration open circulatory system: dorsal contractile heart vessels hemocoel respiration: body surface diffusion trachae- respiratory exchange tubes; spiricles- external openings gills & book lungs- folded epithelium covered by chitin

Nervous System nervous system: annelid-like sensory system: well developed compound eyes & ocelli tympanum tactile & chemo- receptors statocysts

Excretory & Reproductive Systems Excretion: coxal glands- merostomata, arachnids antennal glands-crustacea maxillary glands-crustacea reproduction: dioecious internal fertilization oviparous, oviviparous viviparous direct & indirect development parthenogenesis

Sub-Phylum Trilobitamorpha: Class Trilobita extinct; Paleozoic benthic scavengers segmented compound eyes biramous appendages

Trilobites

Trilobite Diversity

Biramous Appendages

Sub-phylum Chelicerata eurypterids, horseshoe crabs, spiders, and ticks, and mites no antennae or mandibles chelicerae - tear food, venom injection, & secrete enzymes (6) pair of appendages: pedipalps predators/carnivores

Class Merostomata “Horseshoe Crabs”

Class Arachnida first terrestrial metazoans spiders, scorpions, ticks, and mites

Order Aranae (spiders) 35,000 species cephalothorax; no external segmentation; pedipalps- appendages used to hold food; mating silk: (prey capture, egg case, & ballooning) book lungs, trachae or both

Spider Anatomy

Internal Structure

Venomous Species in North America

Day # 3

Day # 6

Day # 9

Day # 10

Order Scorpionida secretive; nocturnal mostly harmless stinger on the telson pectines chelicera chilipeds

Order Pseudoscorpiones

Order Acari (Acarina) mites & ticks reduced segmentation parasites important disease vectors Lyme Disease Rocky Mtn. Spotted Fever Ixodidae- hard ticks

Tick Hypostome

Parasitic Mites

Scabies