ARTHROPODSARTHROPODS

SUBPHYLA: TRILOBITA, SUBPHYLA: TRILOBITA, CRUSTACEA, CHELICERATA, CRUSTACEA, CHELICERATA,

AND UNIRAMIAAND UNIRAMIA

Phylum Arthropoda Phylum Arthropoda “jointed feet”“jointed feet”

Characteristics:Characteristics:– segmentationsegmentation– Jointed, paire appendagesJointed, paire appendages– Exoskeleton – chitinExoskeleton – chitin– CephalizationCephalization– Compound eyesCompound eyes– CoelomCoelom– Open circulatory systemOpen circulatory system– Ventral nerve cordVentral nerve cord

The ExoskeltonThe Exoskelton

The exoskelton is composted of the The exoskelton is composted of the polysaccharide chitin. An arthropod can polysaccharide chitin. An arthropod can not grow without periodically shedding not grow without periodically shedding the exoskeleton. This process is called the exoskeleton. This process is called molting or edcysis. During the few days molting or edcysis. During the few days following the replacement of the following the replacement of the exoskeleton, the animal is extremely exoskeleton, the animal is extremely vulnerable and must hide from vulnerable and must hide from predators. There is also the problem of predators. There is also the problem of desiccation.desiccation.

Advantages & Disadvantages Advantages & Disadvantages of the Exoskeltonof the Exoskelton

AdvantagesAdvantages– ProtectionProtection– SupportSupport– Site for muscle Site for muscle

attachmentattachment– Flexible at the jointsFlexible at the joints

DisadvantagesDisadvantages– HeavyHeavy– Must be moltedMust be molted

Subphylum TrilobitaSubphylum Trilobita

All members of this phylum are All members of this phylum are extinctextinct

Subphylum CrustaceaSubphylum Crustacea

Only arthopods with 2 pair of Only arthopods with 2 pair of appendages on their head that serve appendages on their head that serve as feelersas feelers

Most have 16-20 segments which are Most have 16-20 segments which are fused into several tagmatafused into several tagmata

Most have gills for respirationMost have gills for respiration Most have a free-swimming larva Most have a free-swimming larva

called a naupliuscalled a nauplius

Crustacean DiversityCrustacean Diversity

Subphylum ChelicerataSubphylum Chelicerata

Have piercing and sucking mouth Have piercing and sucking mouth parts called cheliceraeparts called chelicerae

Class ArachnidaClass Arachnida

Include: spiders, scorpions, mites and Include: spiders, scorpions, mites and ticksticks

Cephalothorax and abdomenCephalothorax and abdomen– Cephalothorax – 6 pairs of jointed appendagesCephalothorax – 6 pairs of jointed appendages

1 pair of chelicerae (used to inject venom into 1 pair of chelicerae (used to inject venom into prey)prey)

1 pair of pedipalps (holding food, chewing, & 1 pair of pedipalps (holding food, chewing, & reproductionreproduction

4 pairs of walking legs4 pairs of walking legs 8 simple eyes at anterior end 8 simple eyes at anterior end

AbdomenAbdomen– SpinneretsSpinnerets– RespirationRespiration

Book lungBook lung Tracheae and spiraclesTracheae and spiracles

– Excretory organsExcretory organs Malpighian tubulesMalpighian tubules Coxal glandsCoxal glands

Mites and TicksMites and Ticks

Most abundant and specialized Most abundant and specialized archnidsarchnids

Completely fused head and Completely fused head and cephalothoraxcephalothorax

Subphylum UniramiaSubphylum Uniramia

ClassesClasses– InsectaInsecta– DiplopodaDiplopoda

MillipedesMillipedes 2 pair of legs on each body segment2 pair of legs on each body segment Rounded bodiesRounded bodies Poor vision with a good sense of smellPoor vision with a good sense of smell Feed on plants or decaying plant matterFeed on plants or decaying plant matter Secrete a noxious fluid that contains Secrete a noxious fluid that contains

cyanide when threatenedcyanide when threatened

ChilopodaChilopoda– Flattened bodies with one pair of legs Flattened bodies with one pair of legs

per segment ( except first and last 2 per segment ( except first and last 2 segments)segments)

– May have 15 – 175 pairs of legsMay have 15 – 175 pairs of legs– The appendages on the first segment The appendages on the first segment

are modified into a pair of poison clawsare modified into a pair of poison claws– Long antennae and two clusters of Long antennae and two clusters of

simple eyessimple eyes– Move quickly and feed mostly on Move quickly and feed mostly on

earthworms and other insectsearthworms and other insects