1. Versatile exoskeleton2. Segmentation and appendages for

more efficient locomotion3. Air piped directly to cells4. Highly developed sensory organs5. Complex behavior patterns6. Reduced competition through

metamorphosis

Highly protective, yet highly mobile Exoskeleton: several layers of cuticle

covering secreted by underlying epidermisProcuticle

Inner, thicker cuticle Composed of chitin bound with protein

Tough, resistant, nitrogenous polysaccharide that is insoluble in water, alkalies, and weak acids

Crustaceans procuticle impregnated with calcium salts (<flexibility, >hardness)

Divided into two parts:Exocuticle (secreted before a molt)Endocuticle (secreted after molting)

Epicuticle Thin Composed of protein and lipids

Ecdysis (molting)

Each segment has a pair of jointed appendages can be modified:

Segments and appendages can be specialized for adaptive functions

Limb segments- hollow levers moved by striated muscles (good for rapid actions)

Jointed appendages- equipped with sensory hairs Modified for sensory functions, food

handling, and swift/efficient walking or swimming

Land arthropodsHighly efficient tracheal system of air tubesTubes deliver oxygen directly to tissues and

cells for high metabolic rate

Aquatic arthropodsBreath mainly from some form of gill

Arthropods are very alert to environmental stimuli

Compound (mosaic) eyes Other senses of:

Touch (what organ system?)Smell (what organ system?)Hearing (what organ system?)Balance (what organ system?)Chemical reception (what organ system?)

Innate behaviorUnlearned behavior controls much of what

arthropods do Learned behavior

Habituation (ignore repeated harmless stimuli)

Imprinting (colony scents)Classical conditioning (food scents)Waggle dance (bees)

Larval formsQuite different from adults = less

competition within species

Larval forms adapted for fulfilling a different niche than adults Different foods Different habitats

Subphylum Trilobita Subphylum Chelicerata Subphylum Crustacea Subphylum Myriapoda Subphylum Hexapoda

Extinct for over 200 million years

Abundant during the Cambrian & Ordovican periods

Named for tri-lobed shape of body caused by a pair of longitudinal grooves

Bottom dwellers, probably scavengers

Could roll up like rollie-pollies

Horseshoe crabs, spiders, ticks, mites, scorpions, sea spiders, etc

Characterized by:Two tagmataSix pairs of appendages

Pair of chelicerae Pair of pedipalps Four pairs of walking legs (exception: horseshoe

crabs)No mandiblesNo antennaeMost suck liquid food from their prey

Subclass Xiphosurida Class Pycnogonida Class Arachnida

Order Araneae Order Scorpionida Order Opiliones Oder Acari

Dates from Cambrian periodPractically unchanged back to

Triassic Period Lives in shallow water along

North American Atlantic coast

Swims (awkwardly) with abdominal plates; walks with walking legs

Feed at night – worms & small mollusks

Physical Features:Carapace: Unsegmented,

horseshoe-shaped, and hard dorsal shield

Broad abdomenTelson: long spine-like

tailpieceBook gills: flat leaf-like gills

Exposed on some abdominal appendages

One pair chelicerae and 5 pairs of walking legs

Physical Features: 4 pairs of thin, walking legsPair of ovigers ovigers (ovigerous legs)

Males carry egg masses on these legs Reduced abdomenElongated cephalothoraxLarge suctorial proboscisproboscis: suck juices from

hydroids and soft-bodied animals Ocean-dwellers Few mm in length

uber diverse: > 50,000 species described

Includes: spiders, scorpions, pesudoscorpions, whip scorpions, ticks, mites, harvestmen (daddy longlegs), etc…

Arachnid tagmata: cephalothorax & abdomen

>35,000 species worldwide

Predacious Feed mainly on insects Chase prey, ambush prey, or trap them in silk net Feeding:

Chelicerae function as fangs with ducts from venom glands

Digestive enzymes liquefy tissue so broth can be sucked up

Some have teeth at base of chelicerae to crush or chew in addition to use of enzymes

Physical Features Tagmata joined by pedicelpedicel

Narrow, waist-like structure connecting cephalothorax & abdomen

2 or 3 spinnerets contain hundreds of microscopic tubules connect to abdominal silk silk glandsglands

Silk thread created when liquid protein secretions hardens on contact with air

Fun facts: silk threads stronger than steel threads of same

diameter 2nd in torsional strength (fused quartz fiber is 1st) Threads will stretch 1/5 of their length before

breaking webs used for:

Trap insects, line nests, form sperm webs or egg sacs, build draglines, make bride lines, warning threads, molting threads, attachment discs, nursery webs, or to securely wrap prey

Drag Lines

Orb Webs

Orb Webs

Egg Cases

Most spiders are harmless to humans Australia has some of the deadliest spiders

(they have some of the deadliest organisms actually)Atrax robustis

South America has a few dangerous spiders tooPhoneutria fera

In the U.S.Black widows

Latrodectus mactans Venom is neurotoxic (acts on the

nervous system) Shiny black, red hourglass on ventral

side of abdomen

Brown recluse Loxosceles reclusa Venom is hemolytic

(destroys tissues and skin surrounding bite)

Brown, violin-shaped dorsal stripe on cephalothorax

Book lungsBook lungs or tracheaetracheae (or both) Book lungsBook lungs-- many

parallel air pockets extending into a blood-filled chamber Air enters chamber

by a slit in body wall TracheaeTracheae- system

of air tubes that carry air directly to tissues from opening called spiraclesspiracles

Malpighian tubulesMalpighian tubulesK, other solutes & wastes secrete

into tubulesTubules drain urine-like fluid into

intestinesRectal gland reabsorb K & H20

Wastes like uric acid Nearly dry mixture of urine & feces left

Great adaptation (especially for arid conditions)- conserve fluids

Coxal glandsCoxal glandsModified nephridia open @ base

(coxa) of first & third walking legs

8 simple eyesLens, optic rods, retinaPerception of moving objectsMay form images for hunting/jumping

spidersGenerally poor vision

Sensory setaeHair-like structures that sense surroundings

i.e. air currents, changing tensions in the spider’s web

Web vibrations allow spider to sense size/activity of its prey, mate, or predator

Courtship rituals before mating Indirect mating

Male deposits sperm on a web he has spun prior to mating

Sperm package picked up/stored in cavities of pedipalps

PedipalpsPedipalps = second pair of appendages that males use to transfer sperm into a female’s genital opening

Females can store sperm packets in seminal receptacle until eggs are ready (weeks or months)

Females lay fertilized eggs in silken cocoon Carries around or attaches to web or plant

Cocoon may contain hundreds of eggs Eggs hatch and young remain in egg sac for a

few weeks feeding and growing for several molts

Range: tropical, subtropical, some temperate zones

Secretive: hiding in burrows or under objects by day; feeding @ night

Predacious: insects & spiders Reproduction

Bear live youngMother carries on her back until after their first

molt Venom can be fatal in a few species from

Africa, Mexico, Arizona, New Mexico, Australia, etc…AndroctonusCentruroides

Physical featuresClaw-like pedipalps Jaw-like cheliceraeShort cephalothorax

1 – 6 pairs of eyes appendages

segmented abdomen Preabdomen- broad Postabdomen- tail-like; ends in a stinging

apparatus that injects venom

Physical Features Broad joining of abdomen with cephalothorax

without pedicel Presence of external segmentation of abdomen 4 pairs of long, spindly legs

Legs can regenerate Ends of chelicerae are pincer-like

Scavenger feeders Fun Fact: NOT the

most poisonous spider.They do not even have venom glands!

Habitat: fresh/saltwater, vegetation, ground, parasitic on vertebrates/invertebrates

>25,000 species Many of which are

important to humans

Physical Features Fused cephalothorax & abdomen

(no external tagmatization) CapitulumCapitulum- little anterior

projections carrying mouthparts

Many free livingDermatophoides farinae live in

house dust and cause allergies & dermatoses

Aquatic species (mostly fresh, some marine)Long, hair-like setae on legs for swimmingLarvae may be parasitic on aquatic

inverts

Spider mites (Family Tetranychidae)Agricultural pests on fruit trees, cotton,

clover, etc…

Genus TrombiculaLarvae are called chiggers or redbugsFeed on dermal tissues of terrestrial

vertebrates Process:

Cause irritating dermatitisSome species transmit Asiatic scrub typhus

Genus DemodexHair-follicle mites

FeedingPierce skin; suck

blood until distended; drop off; digest meal

Molts; feeds again Disease vectors

Carry protozoans, rickettsial, viral, bacterial, and fungal organisms

Genus IxodesLyme’s Disease

Genus DermacentorRocky Mountain

spotted fevertularemia

Boophilus annulatus (cattle tick)Texas cattle fever

(red-water fever)

Lobsters, crayfishes, shrimp, crabs, water fleas, copepods, and

barnacles

>67,000 species

Primarily aquatic (mainly marine), few terrestrial

Free living; can be sessile, commensal, parasitic

Important to aquatic ecosystems and economy

2 pairs of antennae Mandible and two pairs of maxillae Typically pair o’ biramous appendages biramous appendages on

each segment (except first antennae) Gills (no malpighian tubules) 16-20 segments (> 60 segments) Major tagmata: head, thorax, abdomen

Varying degrees of fusion CarapaceCarapace- dorsal cuticle of head covers/fuses

with some/all thoracic & abdominal segments; clamshell-like vales that cover most/all body; covers entire cephalothorax not abdomen

FoliaceousFlat & leaf-likemaxillae

Biramous2 branchesSwimmerets, maxillipeds,

uropods, antennae Uniramous

1 branchWalking legs

Swimmerets- abdominal appendages, biramous

Endopod- inner branch of swimmerets Exopod- outer branch of swimmerets Protopod- basal segments, endo/exopods

attached to Maxillipeds- 1st 3 pairs of thoracic appendages Chelipeds- 1st pair of walking legs enlarged

with chela

Gonopods- 1st pair of abdominal swimmerets used for copulation for males, nursery for eggs/young for females

Uropods- last pair of appendages;paddles for backward movement

Telson- uropods & telson protect young/eggs

Epidermis-endocuticle-exocuticle-epicuticle Exoskeleton must be molted during

maturation and growth Molting occurs in steps

1. Old procuticle separates from epidermis, which secretes a new epicuticle

2. As a new exocuticle is secreted, mottling fluid dissolves old endocuticle, and solution products are reabsorbed

3. @ ecdysis, the old epicuticle and exocuticle are discarded

4. In postecdysis, new cuticle is stretched and unfolded and endocuticle is secreted

ChromatophoresChromatophores Pigments in specialized branched cells Change color by:

Concentrating pigment granules in center of cells, which causes lightening

Dispersing pigment throughout each cell, which causes darkening

Neurosecretory hormonesNeurosecretory hormones Neurosecretory cells in eyestalk control Neurosecretory cells in eyestalk control

pigment behaviorpigment behavior Hormones control:Hormones control:

Pigment in eyes for light & dark adaptationPigment in eyes for light & dark adaptation Control rate and amplitude of heartbeatControl rate and amplitude of heartbeat

Androgenic glands Androgenic glands Secretions stimulate expression of male Secretions stimulate expression of male

sexual characteristicssexual characteristics

Controls molting Molt-inhibiting hormone Molt-inhibiting hormone

created by neurosecretory cells in the X-organ of the eyestalk

released through sinus glands in the eyestalk

Level of hormone decreased Molting hormone Molting hormone

produced by Y-organs near mandible Initiates premolt

Mandibles/maxillae involved in ingestion Maxillipeds hold/crushes food Suspension feeders

Plankton, detritus, bacteria Use legs to create water currents that sweep food

particles through fringe of setae Scavengers

Larvae, worms, crustaceans, snails, fishes Predatory

Lygiosquilla- a walking leg has specialized digit that can be drawn into a groove and released to pierce passing prey

Alpheus- enlarged chela that forms bubble that implodes to stun prey (like cocking a gun)

Crayfish2-part stomach

Gastric mill in 1st stomachFood shredded by mandibles ground by 3

calcareous teeth into fine particles that will pass to 2nd stomach

Particles pass into intestines for chemical digestion

Some small crustaceans breath through body surface

GillsVary in shape: tree-like, leaf-like, filamentousAssociated blood vessels or sinusesAttached to appendages usually

Movement through H2O keeps gills ventilated

Branchial chambersBranchial chambers Protected by overlapping carapaceProtected by overlapping carapace

Open circulatory systemHeart (compact or tubular)ArteriesMovement of organs and limbs circulates

blood more effectively in open sinuses than heartbeats and capillaries

Blood May contain respiratory pigments

Hemocyanin (decapods) hemoglobin

Property of clotting to prevent loss of blood in injuries

transport blood to different areas of hemocoel

Excretory & osmoregulatory organs are paired glands in head

Antennal glands/Maxillary Antennal glands/Maxillary glands/green glands glands/green glands (decapods)- Excretory pores opening @ base of antennae or maxillae

Some wastes diffuse through gills as well as excretory glands

Waste products: ammonia with some urea and uric acid

Cerebral ganglion Located above esophagus sends nerves to anterior sense organs Connect to a subesophageal ganglion by a pair of

connectives around esophagus Double ventral nerve cord has a ganglion in

each segment that sends nerves to viscera, appendages, & muscles

Giant fiber systems Sensory organs

Eyes Statocysts- balance organs Tactile setae (on cuticle) Chemosensitive setae (on antennae, antennules, &

mouthparts)

Median (nauplius) eyesMedian (nauplius) eyes2-3 pigment cups containing retinal cellsmay have lensFound in nauplius larvae and in some adults

Compound eyesCompound eyescan be on moveable eyestalks (i.e.

crabs/crayfish)Detect motion, analyze polarized lightWide visual field due to convex corneal

surfaceComposed of ommatidiaommatidia

Mainly dioecious Barnacles monecious (cross-fertilization) Parthenogenic in some ostracods

Most brood their eggs Branchiopods/barnacles- special brood chamber Copepods- attached egg sacs to abdominal sides Malacostracans- carry eggs and young attached

to appendages Life Cycles

Crayfish juvenile small version of adult Most produce larvae that must go through series

of changes as it molts NaupliusNauplius- unsegmented body, frontal eye, three pairs

of appendages (2 pairs of antennae & mandibles) Post-larval forms vary among subphyla

Class BranchiopodaOrder AnostracaOrder NotostracaOrder ConchostracaOrder Cladocera

Class MaxillopodaSubclass OstracodaSubclass CopepodaSubclass BranchiuraSubclass Cirripedia

Class MalacostracaOrder IsopodaOrder AmphipodaOrder

EuphasiaceaOrder Decapoda

Physics FeaturesReduced 1st antennae

2nd maxillae

PhyllopodaPhyllopoda Flattened, leaf-like legs Main respiratory organs Suspension feeding Locomotion

Order Anostraca Fairy shrimp; brine shrimp Lack a carapace

Order Notostraca Tadpole shrimp (i.e. Triops) Carapace forms large dorsal shield covering most

trunk segments Order Conchostraca

Clam shrimp (i.e. Lynceus) Bivalved carapace encloses entire body

Order Cladocera Water fleas (i.e. Daphnia) Carapace covers body, but not head Large portion of freshwater zooplankton

Physical features:Segmented

5 cephalic, 6 thoracic, 4 abdominalTelson Maxillopodan eye in the nauplii

Subclass OstracodaMarine, fresh H2O habitatsClam-like….bivalved carapaceSeveral trunk segments fused# of thoracic appendages reduced to 2 or 0Burrow in sedimentsScavenge food, feed on detritus, suspension

feeding

Subclass CopepodaFree-living in planktonic & benthic

habitats (marine & fresh)10 consumer in many aquatic nichesMany symbiotic, some parasiticSmall, elongate, tapered toward

posteriorLacks carapaceSimple, median, nauplius eye Appendages

4 pairs of flat, biramous, thoracic swimming appendage

5th pair reduced No legs on abdomen

Subclass BranchiuraParasitize marine or freshwater fish5-10 mm longPhysical features:

No gills Broad, shield-like carapace Compound eyes 4 biramous thoracic appendages for swimming Short, unsegmented abdomen 2nd maxillae modified as suction cups

Subclass CirripediaBarnaclesBurrowing or parasitic formsEnclosed shell of calcareous platesSessile as adults

Some can attach to substrate by a stalk Physical features:

Carapace (mantle) surrounds body, secretes calcareous-plated shells

Reduced head No abdomen Long thoracic legs Many-jointed cirri with hair-like setae

Cirri extend through small opening between the plates to filter feed

Largest class of Crustacea & diverse

Marine & freshwater

Physical features:8 thoracic segments6 abdominal

segmentsEach segment has a

pair of appendages

Order IsopodaAsellus- freshwaterLigia- sea beaches, rocky shoresPorcellio & Armadillidium- terrestrial under

stones or damp places (rollie pollies)Some parasites of fish or other crustaceansPhysical features:

Dorsoventrally flattened No carapace Sessile compound yes Gills on abdominal appendages

Order AmphipodaMarine and freshwatersOrchestria- beach fleasPhysical features:

No carapace Sessile compound eyes Compressed laterally gills on thoracic segments

Order Euphausiacea Important as oceanic plankton- “krill”

Uber important in ocean ecosystems3-6 cm longEaten by baleen whales and many fishes

Order DecopodaLobsters, crayfish, shrimps, crabsPhysical features:

5 pairs of walking legs First pair of legs modified to form chelae True crabs have broader carapace & reduced

abdomen

Ura (fiddler crabs) – burrow in sand just below high-tide

Decorator crabs- cover carapace with sponges and sea anemones as camouflage

Libinia (hermit crabs)- live in snail shell; abdomen not protected by exoskeleton

Centipedes, millipedes

2 tagmata: head & trunk

One pair of antennae

Mandibles & 2 pairs of maxillae(1 pair in millipedes)

Uniramous legs

Respiratory system: respiratory exchange through body surface and tracheael systems (aquatic juveniles may have gills)

Centipedes Predators- earthworms, insects Dioecious & oviparous Physical features:

Somewhat flattened dorsoventrallyCan have up to 177 segmentsSegments bear one pair of appendages

First body segment- modified- venom clawsHead with pair of eyesRespiration- tracheal tubes with pair of

spiracles @ each segment

Scutigera15 pairs of legs

Scolopendra21 pairs of legs

“double footed” Millipedes- “thousand feet” Herbivorous Females lay eggs in nest and guards

it Physical features

25-100 segments4 thoracic segments- 1 pair of legsAbdominal segments

2 pairs of legs on each 2 pairs of spiracles on each

Larva have 1 pair of legs per segment