Phylum Arthropoda - West Chester Universitydarwin.wcupa.edu/faculty/boettger/uploads/Main/...Arthropod Characteristic = “jointed limbs” Segmented body = metamerism = grouped into

Phylum Arthropoda

Arthropod Characteristic= “jointed limbs”Segmented body = metamerism= grouped into 2/3 regionsPaired segmented appendagesChitinous exoskeletonTubular alimentary canalCoelom reduced to hemocoelOpen circulatory systemRespiration by gills, tracheaeor spiraclesAnterior ganglion, pairedconnectives & nerve cordsMalphigian tubes = excretionSeparate sexes

Arthropod Fun FactsAphids are born pregnantNo two spider webs are alikeAdult bed bugs can survive 1 yearwithout foodHornet sting has highestconcentration of AChEBed houses 6 billion dust mitesAnt queen can live 15 yearsDragon flies can reach 60 MPHEach year insects eat 1/3 earth’sfood cropCitronella irritates mosquito feetMosqitos prefer children toadults, blondes to brunettes

You are here!

Arthropod Fun FactsLobster blood = blue, insect =yellowFlea leap = greater accelerationthan space shuttleBlack widow venom morepowerful than rattlesnakeParasitic wasp = smaller thanhousefly eyeMore insects in 1 mile2 thanhumans on earthHoneybee kills more people thanpoisonous snakesAmong the deadliest insects arekissing bugs and African ants

Arthropod Generalized Bauplan

1. Longitudinal viewThree distinct sections or tagmata: head, thorax andabdomen (different classes have slightly different names)Head = antennae, mouthparts, tightly fused = cranium =difficult to determine # of segments involvedThorax = locomotor part of the body, three segments(often fused)Abdomen = may or may not contain appendages

Arthropod Generalized Bauplan2. AppendagesLack ciliation formovement = evenduring larval stagesProblem = rigidexoskeletonSolution = appendagesof plates andcylindersSkeleton + muscles =leverageAdapted for differentfunctions on types oflocomotionUni- or biramous

Arthropod Generalized Bauplan

3. Cross sectionLoss of coelom associated with open circulatory systemHemocoel = internal organ are bathed in body fluidsBody size demands pumping organCephalization, ganglions due to metamerism

Arthropod Generalized Bauplan

4. Exoskeleton= secreted by epidermal cellsEpicuticle = outermost, hard protein cross link, waxylipoprotein (cement layer, waxy layer and cuticulin)Procuticle = bulk of exoskeleton, made of exo-andendocuticle, flexible, composed largely of chitin,strengthened by calcium

Moulting or EcdysisInvolvement ecdysone (hormone)

a) Old skeleton detached fromepidermis

b) Epidermis secretes epicuticlec) Enzymes degrade exoskeletond) Secretion of new procuticlee) Old skeleton splitsf) Extrication from old skeletong) “Sclerotinization” = tanningh) Some animals consume old

skeleton

Generalized Bauplan Differentiation

Subphylum Cheliceriformes

Cheliceriformes Characteristics65,000 described speciesSome paleozoic forms were2 m lengthRich fossil recordMost species live on landMites secondarily inhabitedaquatic habitatsBody composed of:Prosoma = cephalothorax (6segments)Opisthosoma = abdomen (12segments)! bearing telsonBook lungs or gills

Cheliceriformes CharacteristicsAppendages: chelicerae,pedipalps, walking legs= multiarticulate/uniramousExcretion by coxal glands/Malphigian tubulesSimple medial eyes,sometimes compund eyesMost gonochoristic/dioecious

Class Chelicerata

Subclass Merostomata

1. Carapace2. Telson3. Compound eye4. Anterior spine

Preserved specimen ofLimulus polyphemus

Called horsefoot by Thomas HariotHarmless and non poisonousTelson used as lever or rudder

Asian horseshoe crabs = delicacy (up to $50/animal,American horseshoe crabs = bait ($1-2/animal)

12

3

1. Chelicera2. Pedipalps3. Walking legs4. Chilaria

1. Genital operculum (covering genital pores)2. Gill opercula (covering book gills)3. Carapace5. 4th chelate walking leg

Ventral view ofabdomen of Limulus.

Hemolymph = analogous to human bloodOxygen carrying protein = hemocyanin

Whelk fishermen use 20-25,000horseshoe crabs annually as bait

Breeding grounds = Delaware Bay

Subclass ArachnidaCarapace-like shieldOpisthosomaappendages modified= spinnerets/pectines

Book lungsAlmost all terrestrialOver 60,000 speciesCarnivorousEyes and tactile hairs

1

2 3

1. Eyes2. Cheliceraewith fangs3. Pedipalps

Spinnerets

The “Joy” of Spider ReproductionGonochoristicSexual dimorphism

Intricate mating duels(other males)CourtshipSperm deposited in webFertilized eggs in silkcocoon

Spider Art

Class Pycnogonida= sea spiders600 speciesCarnivoresDt extendsinto legsCold water