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Arthropodshttp://www.iteachbio.com/Marine-Biology/Arthropods.movArthropodaArthro-joint; pod-footLargest group of animalsSpiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, insects, etc.Found in all types of environmentAll feeding types carnivorous, omnivorous, herbivorousAll arthropods haveExoskeletonSegmented bodyBody segments grouped into specialized regions (= tagmata, plural)Jointed legsAir piped directly to cellsHighly developed sensory organs

ExoskeletonCuticleOuter covering secreted by epidermisComposed of 2 layersBoth layers contain chitinTough, resistant, nitrogenous polysaccharideProcuticleInner, thicker part of cuticleExocuticle secreted before a moltEndocuticle secreted after a moltEpicuticleOuter, thin part of cuticleComposed of protein & lipids

ExoskeletonSome arthropods grow too big for their exoskeletons & must moltMolting (ecdysis) is to leave an exoskeleton and grow a new one5SegmentationTypically each segment has a pair of jointed appendagesLimb segmentsHollow levers, rapid actionJointed appendagesSensory hairs for food handling, swift/efficient walking or swimming

Air Piped Directly to CellsHighly efficient tracheal systems of air tubesDelivers oxygen directly to tissues & cellsCreates a high metabolic rate

GeneralUsually are active, energetic animalsMost abundant and diverse of all animalsGreatest diversity (have no rivals)Most number of speciesWidest ecological distributionThey compete with us for food and spread serious diseasesThey are essential in pollination of many food plantsThey also serve as food, yield drugs and dyesAnd create products like silk, honey, and beeswax

Subphylum Trilobitabecame extinct about 200 million years agothey were bottom dwellers, probably scavengers could roll up like pill bugs

Subphylum Cheliceratavery ancient group including: horseshoe crabs, spiders, ticks and mites, scorpions, sea spiders, and otherscharacterized by presence of 2 tagmata and six pairs of appendagesa pair of cheliceraea pair of pedipalpsfour pairs of walking legsthey have no mandibles or antennaemost suck liquid food from their preyClass Merostomata (Subphylum Chelicerata)(horseshoe crabs)only five living species12 males, 18 females live in shallow water along North American Atlantic coastfeed at night on worms and small molluscsare harmless to humans

Horseshoe Crabs

Horseshoe CrabsClass Pycnogonida (Subphylum Chelicerata)(sea spiders )Move on four pairs of long, thin walking legsFeed by sucking juices from hydroids and soft-bodied animalsOften have a pair of ovigerous legs (ovigers) with which males carry the egg massesCommon in all oceans

Vent Sea SpiderClass ArachnidanOver 50,000 speciesSpiders, scorpions, pseudoscorpions, ticks, mites, harvestmen (daddy longlegs), etcTagmataCephalothorax & abdomenClass ArachnidaOrder Araneae: SpidersOver 35,000 speciesCephalothorax & abdomen show no external segmentationThe tagmata are joined by a narrow, waistlike pedicelPredatorsfeeding mostly on insectsChelicerae function as fangs and bear ducts from their venom glandsSome chase their prey, other ambush them, and many trap them in silk webs

Seizes prey with cheliceraeInjects venomVenom liquefies tissues, allowing spider to suck the broth into the stomachSpiders with teeth crush or chew preyClass ArachnidaOrder Araneae: Spiders

Spiders breathe by book lungs or tracheae (or both)Book lungs many parallel air pockets extending into a blood-filled chamberClass ArachnidaOrder Araneae: Spiders

Excretory SystemMalpighian tubulesWorks in conjunction with specialized rectal glandsPotassium, other solutes, and waste materials are secreted into the tubules, which drain the fluid, or urine into the intestinesRectal glands reabsorb most of the potassium and waterproducing a nearly dry mixture of urine and feces

Class ArachnidaOrder Araneae: Spiders

Eight Simple Eyes (poor vision)Each provided with a lens, optic rods, and retinaPerceive moving objectsSome may form imagesSensory setaeHairlike structure to aid in awareness of its environmentSetae communicate information about SurroundingsAir currents, changing tensions in webClass ArachnidaOrder Araneae: Spiders

Web-Spinning HabitsSilk glandsFound in 2-3 pairs of spinneretsEmits a protein secretion as a liquid; hardens on contact with air to form a silk threadStronger than steel threads (same diameter)Silk threads used for trapping insectsLine their nestsForm sperm webs or egg sacsWarning threads, molting threads, nursery websWrap prey securelyClass ArachnidaOrder Araneae: Spiders

Spider WebClass ArachnidaOrder Araneae: SpidersAre Spiders Really DangerousTimid creatures; more of an allies in the conflict with insectsVenom usually harmless to humansBite only when threatened or defending eggs or youngTwo genera (in the United States) can give severe or fatal bitesBlack widows (Latrodectus mactans)Brown recluse (Loxosceles reclusa)Black widowModerate to small in sizeShiny black, with a bright orange or red hourglass on the underside of their abdomenVenom is neurotoxicActs on the nervous system4-5 of each 1000 bites are reported fatalClass ArachnidaOrder Araneae: Spiders

Brown RecluseSmaller than black widowsBrown, and bear a violin-shaped dorsal stripe on their cephalothoraxVenom is hemolyticdestroying tissues and skin surrounding a biteBite can be mild to serious and occasionally fatal

Class ArachnidaOrder Araneae: Spiders

Brown Recluse Bite

Brown Recluse Bite

Brown Recluse BiteClass ArachnidaOrder Scorpionida: ScorpionsCommon in tropical & subtropical regionsGenerally secretiveFeed on insects & spidersSeize with clawlike pedipalps & rip with jawlike cheliceraeShort cephalothoraxBears appendages1-6 pairs of eyeAbdomenPreabdomenPostabdomenTail-like structure ending in a stinging apparatusInjects venom (most are not harmful to humans)

Great Hairy Scorpion largest in US (up to 6)

Scorpions glow under black lightClass ArachnidaOrder Opiliones: Harvestmendaddy longlegsBroad joining of the abdomen & cephalothorx4 pairs of long spindly legsCan cast off legs if grasped by a predatorChelicerae are pincherlikeFeed mostly as scavengers

Cephalothorax & Abdomen completely fusedCapitulumAnterior projection that carries mouth partsFound everywhere, over 25,000 speciesClass ArachnidaOrder Acari: Ticks & Mites

Mites sometimes cause allergies and dermatosesAgricultural pestsFeed on dermal tissue of terrestrial vertebratesTicks Larger than mitesSuck blood until enormously distendedare among the worlds premier disease vectors, second only to mosquitoes (Lyme disease, Rocky Mountain spotted fever, tularemia, Texas cattle fever, etc)

Class ArachnidaOrder Acari: Ticks & Mites