Trilobites, Chelicerates, and Myriapods Trilobites, Chelicerates, and Myriapods

Trilobites, Trilobites, Chelicerates, and Chelicerates, and

MyriapodsMyriapods

Trilobites, Trilobites, Chelicerates, and Chelicerates, and

MyriapodsMyriapods

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

19-2


Japanese Spider Crap4 M in length

Follicle Mite0.1 mm in length


19-4

Relationships among arthropod subgroupsRelationships among arthropod subgroups Divided into Divided into subphylasubphyla

Centipedes, millipedes are placed into Centipedes, millipedes are placed into subphylum subphylum MyriapodaMyriapoda

Insects are placed in subphylum Insects are placed in subphylum HexapodaHexapoda

Spiders, and ticks form subphylum Spiders, and ticks form subphylum ChelicerataChelicerata

Lobsters, crabs, barnacles, and others Lobsters, crabs, barnacles, and others form subphylum form subphylum CrustaceaCrustacea

CharacteristicsCharacteristics



19-6

2 Important Parts in Arthropods:

Appendages andMouthparts

Uniramous: single branchedBiramous: 2 branches

Chelicerae: pointed appendages to grasp food

Mandible: chewing appendage


19-7

Arthropod CharacteristicsArthropod Characteristics

WHY HAVE ARTHROPODS SURVIVED…(Top 5 WHY HAVE ARTHROPODS SURVIVED…(Top 5 Reasons) - 600 million years oldReasons) - 600 million years old

1. Versatile Exoskeleton 1. Versatile Exoskeleton Cuticle is protective and jointed, providing mobilityCuticle is protective and jointed, providing mobility Consists of inner thick molting Consists of inner thick molting procuticle (made of procuticle (made of

exocuticle and endocuticle) exocuticle and endocuticle) and outer thin and outer thin epicuticleepicuticle

Ecdysis,Ecdysis, or molting or molting Process of shedding outer covering and growing a new, Process of shedding outer covering and growing a new,

larger onelarger one Arthropods typically molt Arthropods typically molt four to sevenfour to seven times times

Controlled by hormones and environmental cuesControlled by hormones and environmental cues


19-8


19-9

2. Segmentation and Appendages2. Segmentation and Appendages Paired Appendages specialized for Paired Appendages specialized for

division of labor division of labor ((sensing, food handling, sensing, food handling, walking, or swimming)walking, or swimming)

3. Metamorphosis3. Metamorphosis Larvae and adults feed on different Larvae and adults feed on different

organisms and occupy different habitats organisms and occupy different habitats Avoid competitionAvoid competition

Survival of ArthropodsSurvival of Arthropods


19-10

4. Air Piped Directly to Cells4. Air Piped Directly to Cells Terrestrial arthropods Terrestrial arthropods

Use tracheal system for oxygen transport Use tracheal system for oxygen transport directly to tissuesdirectly to tissues

Aquatic arthropodsAquatic arthropods Respire via gillsRespire via gills

5. Highly Developed Sensory Organs5. Highly Developed Sensory Organs Eyes vary from simple light sensitive ocelli to a Eyes vary from simple light sensitive ocelli to a

compound mosaic eyecompound mosaic eye Other sensory structures for touch, smell, Other sensory structures for touch, smell,

hearing, balancing, and chemical receptionhearing, balancing, and chemical reception

Survival of ArthropodsSurvival of Arthropods


19-11

Early Arthropod fossils: Trilobites and EurypteridSubphylum Trilobita - extinct for over 200 million years


19-12

Subphylum ChelicerataSubphylum Chelicerata

Chelicerata CharacteristicsChelicerata Characteristics Chelicerates have Chelicerates have six pairssix pairs of of

cephalothoracic appendages including cephalothoracic appendages including chelicerae chelicerae (eating),(eating), pedipalps pedipalps (mating)(mating) and and four pair of legsfour pair of legs

Lack mandibles and antennaeLack mandibles and antennae Most suck liquid food from preyMost suck liquid food from prey Example: spiders, horseshoe crabs, sea Example: spiders, horseshoe crabs, sea

spiders, ticks, scorpionsspiders, ticks, scorpions


19-13

Sea Spiders

Spiders

Horseshoe Crabs


19-14

Horseshoe Crab: Illustrating 6 pairs of appendages


19-15

Sea spiders: Illustrating 6 sets of appendages

Oviger: In males only, carry developing eggs


19-16

Class ArachnidaClass Arachnida Structures Structures Divided into two body parts: Divided into two body parts: a cephalothorax a cephalothorax

and an abdomenand an abdomen Cephalothorax bears ALL appendagesCephalothorax bears ALL appendages Example: Spiders, Ticks, and ScorpionsExample: Spiders, Ticks, and Scorpions



19-17

Most are Most are predaceouspredaceous and have claws, fangs, and have claws, fangs, poison glands, or stingerspoison glands, or stingers

Sucking mouthparts ingest fluids and soft Sucking mouthparts ingest fluids and soft tissues from bodies of their preytissues from bodies of their prey

PedipalpsPedipalps of males are modified, sometimes of males are modified, sometimes elaborately, for sperm transferelaborately, for sperm transfer



19-18

Most harmless to humans and provide Most harmless to humans and provide essential control of injurious insectsessential control of injurious insects

Some spiders are venomous and can Some spiders are venomous and can cause pain or death in humanscause pain or death in humans

Ticks may carry Ticks may carry human diseaseshuman diseases Mites can be Mites can be crop pestscrop pests



19-19

Order Araneae: SpidersOrder Araneae: Spiders Approximately 40,000 species Approximately 40,000 species Body consists of an Body consists of an unsegmented unsegmented

cephalothoraxcephalothorax and and abdomenabdomen Anterior appendages are a pair of chelicerae Anterior appendages are a pair of chelicerae

with terminal fangswith terminal fangs Pair of Pair of pedipalps pedipalps are used by males to are used by males to

transfer sperm and handle foodtransfer sperm and handle food Four pairs of walking legs terminate in clawsFour pairs of walking legs terminate in claws All are predaceous,All are predaceous, mostly on insects mostly on insects



19-20

External Anatomy of Jumping Spider


19-21

Injected venom liquefies and digests the tissues which Injected venom liquefies and digests the tissues which is sucked into spider’s stomachis sucked into spider’s stomach

RESPIRATORY SYSTEM (Book lungs or Trachea)RESPIRATORY SYSTEM (Book lungs or Trachea) Book lungsBook lungs unique to spiders unique to spiders

Parallel air pockets extend into blood-filled chamberParallel air pockets extend into blood-filled chamber Air enters chamber through a slit in body wallAir enters chamber through a slit in body wall

Trachea systemTrachea system Transports air directly to tissues/blood through an opening Transports air directly to tissues/blood through an opening

called a called a spiraclespiracle Excretory SystemExcretory System

In spiders and insects, In spiders and insects, Malpighian tubulesMalpighian tubules serve as excretory serve as excretory structures structures



19-22

Internal Anatomy of a Spider


19-23

Sensory SystemsSensory Systems Most spiders have Most spiders have eight simple eyes,eight simple eyes, each each

with a lens, optic rods, and a retina with a lens, optic rods, and a retina Detect movement and may form images Detect movement and may form images

(overall poor vision)(overall poor vision) Sensory hairs detect air currents, web Sensory hairs detect air currents, web

vibrations, and other stimulivibrations, and other stimuli



19-24

Web-Spinning HabitsWeb-Spinning Habits Spinning silk critical ability for spiders Spinning silk critical ability for spiders Two or three pairs of Two or three pairs of spinneretsspinnerets contain contain

microscopic tubes that run to microscopic tubes that run to silk glandssilk glands Liquid scleroproteinLiquid scleroprotein secretion hardens as secretion hardens as

it is extruded from spinneretsit is extruded from spinnerets Silk threads are very strong and will Silk threads are very strong and will

stretch considerably before breakingstretch considerably before breaking Silk is used for orb webs, lining burrows, Silk is used for orb webs, lining burrows,

forming egg sacs, and wrapping preyforming egg sacs, and wrapping prey



19-25

Grasshopper snared in Golden Garden Spider silk.If the spider is not hungry, it will save the live prey for later.


Fisher Spider: Catches prey, paralyzes them, pumps in digestive enzymes,

then sucks out predigested contents.


19-27

ReproductionReproduction Before mating, male stores sperm in Before mating, male stores sperm in

pedipalpspedipalps Mating involves inserting pedipalps into Mating involves inserting pedipalps into

the female genital openingsthe female genital openings Use a Use a courtship ritualcourtship ritual Eggs may develop in a cocoon in the web Eggs may develop in a cocoon in the web

or carried by femaleor carried by female Young hatch in about two weeks and may Young hatch in about two weeks and may

molt before leaving the egg cocoonmolt before leaving the egg cocoon



19-28

Wolf spider with egg sack

Black Widow with egg sack


19-29

Are spiders really dangerous? Are spiders really dangerous? American tarantulasAmerican tarantulas rarely bite, and bite is not rarely bite, and bite is not

dangerous dangerous Species of Species of black widow spidersblack widow spiders are dangerous are dangerous

Venom is a neurotoxinVenom is a neurotoxin Brown recluse spiderBrown recluse spider

Hemolytic venom that destroys tissue around Hemolytic venom that destroys tissue around the bitethe bite

Some Australian and South American spiders are Some Australian and South American spiders are the most dangerous and aggressivethe most dangerous and aggressive



19-30

Tarantula: Not Dangerous. Bite similar to Bee StingBite when threatened or defending eggs/young.


19-31

A: Black Widow displaying Red HourglassB: Brown Recluse Spider displaying violin marking on cephalothorax


19-32

Order Scorpionida: ScorpionsOrder Scorpionida: Scorpions

Approximately 1,400 species worldwideApproximately 1,400 species worldwide Nocturnal and feed largely on insects and Nocturnal and feed largely on insects and

spidersspiders Sand-dwellers locate prey by detecting Sand-dwellers locate prey by detecting

surface waves with leg hairssurface waves with leg hairs Appendages attached to cephalothorax Appendages attached to cephalothorax

Pair of medial eyes and lateral eyesPair of medial eyes and lateral eyes PreabdomenPreabdomen has 7 segments has 7 segments PostabdomenPostabdomen has long, slender tail of five has long, slender tail of five

segments that ends in a stinging apparatussegments that ends in a stinging apparatus



Scorpion epicuticle is fluorescent when exposed to UV light.


19-34

StingerStinger on last segment has venom that on last segment has venom that varies from mildly painful to dangerousvaries from mildly painful to dangerous

Perform complex Perform complex mating dancesmating dances

Ovoviviparous or viviparousOvoviviparous or viviparous and produce from 1 to and produce from 1 to 100 young100 young Gestation is from several months to a yearGestation is from several months to a year



19-35

Emperor Scorpion with young. Young stay with mother until their first molt.

(Gestation is up to a year, and 1 month on back)Life span of a scorpion is about 15 years

Harvestmen: Order OpilionesAKA- Daddy Longlegs


19-36

Order Opiliones: HarvestmenOrder Opiliones: Harvestmen Harvestmen or Harvestmen or daddy longlegsdaddy longlegs Approximately 5,000 species worldwideApproximately 5,000 species worldwide Unlike spiders, abdomen and cephalothorax join Unlike spiders, abdomen and cephalothorax join

broadlybroadly Can lose most of their eight long legs without ill Can lose most of their eight long legs without ill

effecteffect Chelicerae are pincerlike - can’t bite a humanChelicerae are pincerlike - can’t bite a human Are NOT venomous to humansAre NOT venomous to humans Mostly Mostly scavengers scavengers Have 2 eyes, not 8Have 2 eyes, not 8



19-37

Order Acari: Ticks and MitesOrder Acari: Ticks and Mites Medically and economically the most Medically and economically the most

important arachnidsimportant arachnids About 30,000 species have been described About 30,000 species have been described Most mites are less than 1 millimeter longMost mites are less than 1 millimeter long Ticks may range up to 2 cmTicks may range up to 2 cm Complete fusionComplete fusion of cephalothorax and of cephalothorax and

abdomen abdomen No sign of external segmentationNo sign of external segmentation



19-38

Mouthparts on tip of the anterior Mouthparts on tip of the anterior capitulumcapitulum Chelicerae on each side help pierce, tear, or Chelicerae on each side help pierce, tear, or

grip foodgrip food Adult mites and ticks possess 4 pairs of legsAdult mites and ticks possess 4 pairs of legs Transfer sperm directly or by Transfer sperm directly or by

spermatophores spermatophores (packets of sperm)(packets of sperm)



19-39

Wood TickAll stages are ectoparasites

Red Velvet Mite: TrombiculaSimilar to chiggers, only Larvae

is ectoparasite. Nymphs and Adults are free-living.


19-40

House dust mites House dust mites Free-living and often cause allergiesFree-living and often cause allergies

Spider mites Spider mites One of many important agricultural pest mites One of many important agricultural pest mites

that suck out plant nutrientsthat suck out plant nutrients Chiggers Chiggers

Larval stage feed on dermal tissues and cause Larval stage feed on dermal tissues and cause skin irritationskin irritation

Hair follicle mite Demodex Hair follicle mite Demodex Harmless but may cause mild dermatitisHarmless but may cause mild dermatitis



19-41

Human Follicle Mite


19-42

Human itch miteHuman itch mite Causes intense itching Causes intense itching Popular in WWII - due to crowded conditions in Popular in WWII - due to crowded conditions in

which people lived (Scabies)which people lived (Scabies)


Human Itch Mite



Ticks:Ticks: 2nd premier disease vector (after mosquito). 2nd premier disease vector (after mosquito). Some carry Lyme disease (bacteria)Some carry Lyme disease (bacteria)

Bacterial infection dicovered in 1970, in the Bacterial infection dicovered in 1970, in the city of Lyme, Conneticut. city of Lyme, Conneticut.

Transmit Rocky Mountain spotted fever (bacteria)Transmit Rocky Mountain spotted fever (bacteria)Transmits Texas cattle fever (Protozoan)Transmits Texas cattle fever (Protozoan)


19-44

Tick: Carries Texas Cattle Fever


19-45

Subphylum MyriapodaSubphylum Myriapoda

CharacteristicsCharacteristics Myriapods (“Many Footed”) include: Myriapods (“Many Footed”) include:

Chilopoda (centipedes)Chilopoda (centipedes) Diplopoda (millipedes)Diplopoda (millipedes)

Use trachea to transport respiratory gases to Use trachea to transport respiratory gases to all body tissue all body tissue

Excretion usually by Malpighian tubulesExcretion usually by Malpighian tubules


19-46


19-47

Class ChilopodaClass Chilopoda CentipedesCentipedes Found under logs, bark and stonesFound under logs, bark and stones Carnivorous,Carnivorous, eating earthworms, cockroaches, eating earthworms, cockroaches,

and other insects (use poison claw) and then and other insects (use poison claw) and then chew prey with chew prey with mandiblemandible

Centipedes have one pair of legs on each Centipedes have one pair of legs on each segment (except 1st and last 2)segment (except 1st and last 2)

Most harmless to humansMost harmless to humans Few large, tropical centipedes are dangerousFew large, tropical centipedes are dangerous

Approximately 3,000 species worldwideApproximately 3,000 species worldwide



19-48

Centipede from Amazon, Peru. Head of a Centipede


19-49

Characteristics Characteristics

Appendages of first body segment form Appendages of first body segment form poison claws - comparable to wasp stingpoison claws - comparable to wasp sting

Head has one pair of Head has one pair of antennaeantennae Eyes on either side of the head consist of Eyes on either side of the head consist of

ocellusocellus



19-50

ReproductionReproduction Sexes separateSexes separate Most lay eggs and guard them (oviparous), Most lay eggs and guard them (oviparous),

few are viviparousfew are viviparous Young resemble adults and Young resemble adults and do not undergo do not undergo

metamorphosismetamorphosis Legs and segments are added with each moltLegs and segments are added with each molt



19-51

Class DiplopodaClass Diplopoda Millipedes (double footed) -Millipedes (double footed) -10,000 species10,000 species Less active than centipedesLess active than centipedes

Walk with graceful rather than wriggling motionWalk with graceful rather than wriggling motion Most eat decayed plants but a few eat living Most eat decayed plants but a few eat living

plant tissue - use mandibleplant tissue - use mandible Most are slow moving and roll into a coil for Most are slow moving and roll into a coil for

defensedefense Some Some secrete toxic or repellant fluidssecrete toxic or repellant fluids from from

special glands on side of body (hydrogen special glands on side of body (hydrogen cyanide)cyanide)



19-52

Tropical millipede. Head of a Millipede


19-53

Characteristics Characteristics Cylindrical bodiesCylindrical bodies with 25 to more than with 25 to more than

100 segments100 segments Short thorax consists of 4 segments, Short thorax consists of 4 segments,

each bearing one pair of legseach bearing one pair of legs Each abdominal segment has 2 sets of Each abdominal segment has 2 sets of

legslegs Head has 2 clusters of simple eyes and Head has 2 clusters of simple eyes and

a pair of antennae and mandiblesa pair of antennae and mandibles



19-54

ReproductionReproduction Appendages of seventh segment specialized Appendages of seventh segment specialized

as as copulatory organscopulatory organs After copulation, female lays eggs in a nest After copulation, female lays eggs in a nest

and guards themand guards them Larvae have only one pair of legs per Larvae have only one pair of legs per

segment, as they molt more legs and body segment, as they molt more legs and body segments are acquiredsegments are acquired



19-55

Classification- Phylum ArthropodaClassification- Phylum Arthropoda Subphylum Trilobita (extinct)Subphylum Trilobita (extinct) Subphylum ChelicerataSubphylum Chelicerata

Class ArachnidaClass Arachnida Order AraneaeOrder Araneae Order ScorpionesOrder Scorpiones Order Opiliones (Daddy Longlegs)Order Opiliones (Daddy Longlegs) Order Acari (Ticks and Mites)Order Acari (Ticks and Mites)

Subphylum MyriapodaSubphylum Myriapoda Class DiplopodaClass Diplopoda Class ChilopodaClass Chilopoda

Subphylum CrustaceaSubphylum Crustacea Subphylum HexapodaSubphylum Hexapoda

ClassificationClassification

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Trilobites, Chelicerates, and Myriapods Trilobites, Chelicerates, and Myriapods