Arthropods 1

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ArthropodsArthropods


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Phylum

Arthropoda

Class

Crustacea

Class

Arachnida

Class

Insecta


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CharacteristicCharacteristics ofs ofArthropodsArthropods


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1. EXOSKELETON1. EXOSKELETON

In most arthropods the body is coveredwith chitinous cuticle that is hardened intoan exoskeleton. Once the cuticle is

hardened it ca

n

not i

ncrease i

nsize

.Someregions of the cuticle remain unhardened

to allow flexibility and movement.


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2.2.METAMERISMMETAMERISM

Body composed ofnumeroussegments, segmented condition may

be concealed

.

Inthe primitiveArthropod, the body was thought to

be a series of metameres, each,except for the first and last, with a

pair of appendages.


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3. JOINTED APPENDAGES3. JOINTED APPENDAGES

Jointed appendages give arthropodsnumerous specialized organs for

walking, graspi

ng, a

nd eati

ng

.


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4. VENTRAL NERVE COR4. VENTRAL NERVE CORDD Ventral nerve cord with ganglia at

each segment. Only the brain (most

an

terior) gan

glia is above thedigestive system.


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5.5. OPEN CIRCULATORYOPEN CIRCULATORYSYSTEMSYSTEM

A dorsal (upper) vessel directs bloodforward toward the brain.


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6.DIGESTIVE ANDEXCRETORY6.DIGESTIVE ANDEXCRETORY

SYSTEM

SSYSTEM

S


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8. RESPIRATORY SYSTEM8. RESPIRATORY SYSTEM

IS DIFFERENT: GILLS IN AQUATICFORMS AND TRACHEAEIN

TE

RRE

STI

AL

F

ORM

S


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7.7. SEXUALSEXUALREPRODUCTIONREPRODUCTION

However, some insects areparthenogenic, females produce

offspring without mating.


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Complete and incomplete

metamorphosis

Egg

Larva

Pupa

Adult

Egg

Larva

Adult


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Medical importance ofMedical importance ofArthropodsArthropods

Intermediate hosts for some humanparasites

Venomous animals Human permanent or temporary

parasites

Vectors of huma

ninfectio

ns

Cause of allergy


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Phylum

Arthropoda

Class

Crustacea

Class

Arachnida

Class

Insecta


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CLASS CRUSTACEACLASS CRUSTACEAShrimpShrimpss, lobsters, and crabs, lobsters, and crabs

(derivation: crust(derivation: crust == hard, shellhard, shell--like; 26,000 known species).like; 26,000 known species).

Two pairs of antennae

Two body regions (head and thoraxcombined into the cephalothorax)

One pair of appendages per body

segment

.Appe

ndages termi

nate i

npinchers.

Primarily an aquatic group, respiration isby gills even in terrestrial species.


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FreshFresh--water crabs arewater crabs are

intermediate hosts forintermediate hosts forParagonimus westermaniParagonimus westermani


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wat

Cyclops are intermediate hosts forCyclops are intermediate hosts forDiphylobothrium latum andDiphylobothrium latum and

Dracunculus medinensisDracunculus medinensis


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CLASS ARACHNIDA.CLASS ARACHNIDA.Spiders, ticks, mites, scorpions,Spiders, ticks, mites, scorpions,

derivation:derivation: arachne=spider;arachne=spider;57,000 known species).57,000 known species).

No antennae

Presence of chelicerae, appendages justabove/in front of the mouth.

Most with a cephalothorax and abdomen.

Some with a single body region. Most are terrestrial

Most are predacious.


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Order ScorpionsOrder Scorpions

There are about 2,000 species of

scorpions, found widely distributed

south of about 49 N, except New

Zealand and Antarctica.


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Scorpion

The body of a

scorpion is divided

into two parts: thecephalothorax

(also called the

prosoma) and the

abdomen(opisthosoma).


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Unlike the majority of arachnidspecies, scorpions are viviparous.The young are born one by one, andthe brood is carried about on itsmother's back until the young haveundergone at least one moult.


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The vThe venomenom ofof

scorpionsscorpions All known Scorpion species possess poison

or venom. Scorpions use their venom to kill

or paralyze their prey so that it can beeaten; in general it is fast-acting, allowingfor effective prey capture.

Scorpions rarely aggressively attack

humans, but will often reflexively strikewhen they are handled, stepped on in barefeet, or accidentally crushed in clothing.


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Scorpions produce two types ofvenom:

Hemolytic - i

nduces bur

ning,swelling and necrosis at the wound

site.

Neurotoxic produces intense painat the site of the sting and causeschills, excessive salivation, vomitingand sometimes respiratory paralysis


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Initial treatmentInitial treatment

Application of ice to the wound site

Tourniquet above the wound

Specific antiserum

Prevention: elimination of rubbish

piles favored hiding and breedingplaces of scorpions.


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Order AraneidaOrder Araneida

(spiders)(spiders)


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Venomous spidersVenomous spiders

Latrodectus is a genus that containsapproximately 31 recognized

species of venomous spider. The

commonname widowspiders isoften used to refer to members of

the genus. The Black Widowspiders are well known members

of the genus. The female blackwidow's venom is particularlyharmful to humans (males almost

never bite humans).


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L. tredecimguttatusL. tredecimguttatus femalefemale


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A Black Widow spider with her eggA Black Widow spider with her eggsacs. Taken inMexico.sacs. Taken inMexico.


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The black widow bite.BitesThe black widow bite.Bitesare initially painlessare initially painless


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The venom acts at nerve endings toprevent relaxation of muscles, causing

tetany co

nsta

nt, stro

ng, pai

nful musclecontractions. Thus initial pain is often

followed by severe muscle cramps.Contraction of musculature may extend

throughout the body, though cramping inthe abdomen is frequently the mostsevere.

Standardtreatments usuallyinvolvesymptomatic therapywithpainmedication,musclerelaxants,andantivenom.


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WhilenofatalitieshavebeenattributedtoWhilenofatalitieshavebeenattributedtotarantulatarantula bites,sometimesspiderbitesarebites,sometimesspiderbitesare

regardedastheprobablesourceofinfectionsregardedastheprobablesourceofinfections..

Tarantula

Gallery


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Order AcarinaOrder Acarina

(ticks and mites)(ticks and mites)


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Acarina or Acari are aAcarina or Acari are an ordern order ofofarachnids that containsarachnids that contains mites and ticksmites and ticks..

The diversity of the Acari is extraordinaryThe diversity of the Acari is extraordinary..Most acarines are minute to small (e.g. 0.08Most acarines are minute to small (e.g. 0.08

1.01.0 mm), but the largest Acari (some ticksmm), but the largest Acari (some ticksand red velvet mites) may reach lengths ofand red velvet mites) may reach lengths of

10102020 mm.mm.

It is estimated that over 50,000 species haveIt is estimated that over 50,000 species havebeen described and that a million or morebeen described and that a million or more

species are currently living.species are currently living.

Life-cycle:egglarvanymph adult.Larvahas sixlegs,nymphandmature

tick haveeightlegs


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Ticks are ectoparasites, living by

hematophagy on the blood ofmammals, birds, and

occasionally reptiles and

amphibians. Ticks are importantvectors of a number of diseases,including Lyme disease and Tick-

borne meningoencephalitis.


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Hard ticksHard ticks possess apossess a

scutumscutum -- tough leathertough leather--like integument, thatlike integument, thatcovers most of theircovers most of their

body.body.

Family Ixodidae


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She and he


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A tick (female) sucks bloodA tick (female) sucks blood


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After that she becomes 200After that she becomes 200times largertimes larger


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Some examples ofIxodidaeSome examples ofIxodidaefamilyfamily


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Lonestarticks(Amblyommaamericanum) have been linked to

tran

smission

of ehrlichiosis,tularemia, and southern tick-associated rash illness (STARI). Thesaliva of these ticks is irritating, and

can cause an allergic reaction at thesite of the bite

l kl d ( d ) i k


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Blacklegged (ordeer)ticks(Ixodes scapularis and Ixodes

pacificus) can

tran

smit several tick-borne diseases includinganaplasmosis, babesiosis and Lymedisease. An adult tick is pictured at

left, though it is the smaller nymphalstage ticks which most commonlybite humans.

i d i k (


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Americandogtick (Dermacentorvariabilis) as well as the RockyM

oun

tain

wood tick (D

ermacentorandersoni) can transmit manydiseases including Rocky Mountainspotted fever and tularemia.


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Softticks. FamilySoftticks. FamilyArgasidaeArgasidae


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Fami y Argasi ae Ornit o orusFami y Argasi ae Ornit o orus


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Fami y Argasi ae. Ornit o orusFami y Argasi ae. Ornit o orusspp.spp.


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FamilytrombiculidaeFamilytrombiculidae


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Diseases transmitted by ArachnidsDiseases transmitted by Arachnids(some examples)(some examples)

Arachnida(vector)

Disease

Ixodes Viral encephalitis, Lyme disease,

Japanese spotted fever

Dermacentor Tularemia, Q-fever, RockyMountain spotted fever,

Colorado tick feverOrnithodorus Relapsing fever

Trombiculidae Tsutsugamushi disease


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Prevention against ticksPrevention against ticks


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MitesMites intracutaneousintracutaneousparasitesparasites


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Sarcoptes scabieiis a mite whichburrows into human skin and causesscabies.

The disease produces intense, itchyskin rashes when the impregnatedfemale tunnels into the stratumcorneum of the skin and depositseggs in the burrow. The larvae,which hatch in 310 days, moult intoa nymphs, and then mature intoadult mites. They live 34 weeks.


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0.5 mm


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In the skinIn the skin


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An itch mites passageAn itch mites passage

Demodex folliculorumDemodex folliculorum


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Demodex folliculorumDemodex folliculorumThe Follicle (or Eyelash) MiteThe Follicle (or Eyelash) Mite

Demodex folliculorum is host-

specific obligate ectoparasite living

respectively in the niche

environments of hair follicles andsebaceous glands around the face

and head. Generally their presence

goes totally unnoticed but in some

cases heavy infestations arebelieved to be the cause of certain

forms of hair loss and such skin

complaints as 'acne rosacea'.

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Demodex folliculorumDemodex folliculorum


D d iD d i


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DemodecosisDemodecosis

Tiny invisible acariTiny invisible acari dustdust


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Tiny invisible acariTiny invisible acari dustdustmitesmites can cause allergycan cause allergy

D t it b d h tD t it b d h t


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Dust mites on a bedsheetDust mites on a bedsheet

WHO DID YOU SLEEPWITH LAST NIGHT??

MEDICAL IMPORTANCE OFMEDICAL IMPORTANCE OF


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MEDICALIMPORTANCE OFMEDICALIMPORTANCE OFARACHNIDS:ARACHNIDS:

Venomous animals (spiders andscorpions)

Intracutaneous parasites (Sarcoptesscabiei and Demodex folliculorum)

Ectoparasites and vectors fordiseases (blood-sucking ticks)

Cause of allergy (dust mites)


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CLASS INSECTACLASS INSECTAInsectsInsects

(derivation: in=into, sect=cut;(derivation: in=into, sect=cut;750,000 known species)750,000 known species) Single pair of antenna

Three body regions (head, thorax, and

abdomen) Three pairs of legs (adult insect), one on

each segment of thorax

Most adult insects with wings

roleofinsectswillbethesubjectofournextlecture


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Arthropods 1