Biology 320Biology 320Invertebrate ZoologyInvertebrate Zoology

Fall 2005Fall 2005

Chapter 19 – Phylum Arthropoda, Chapter 19 – Phylum Arthropoda,

Subphylum CrustaceaSubphylum Crustacea

Introduction to CrustaceansIntroduction to Crustaceans

42,000 species42,000 species

Crabs, shrimps, lobsters, and Crabs, shrimps, lobsters, and barnaclesbarnacles

Important ecologicallyImportant ecologically• ZooplanktonZooplankton

Mainly marine, but some FW and Mainly marine, but some FW and a few terrestrial varietiesa few terrestrial varieties

Mandibulates, along with Mandibulates, along with myriapods and insectsmyriapods and insects

Two pairs of antennaeTwo pairs of antennae

Body FormBody Form Two tagma in mostTwo tagma in most

Two pairs of antennaeTwo pairs of antennae• 11stst and 2 and 2ndnd antennae antennae

MandiblesMandibles

Two pairs of maxillaeTwo pairs of maxillae• 11stst and 2 and 2ndnd maxillae maxillae

Lateral compound Lateral compound eyeseyes• Often on eyestalksOften on eyestalks

PereopodsPereopods• Walking legsWalking legs

PleopodsPleopods• SwimmeretsSwimmerets

UropodsUropods• Make up tail finMake up tail fin

Exoskeleton Exoskeleton typically typically mineralizedmineralized• CalcifiedCalcified

Nutrition and Digestive SystemNutrition and Digestive System

Many strategies; feed on Many strategies; feed on suspended particles, suspended particles, detritus, carrion, plants detritus, carrion, plants and/or animalsand/or animals

Possess several Possess several mouthpartsmouthparts• Usually have gnathobasesUsually have gnathobases• Coxae of appendages Coxae of appendages

forms a food grooveforms a food groove

Many use a structure Many use a structure called a setal comb to filter called a setal comb to filter feedfeed• Often located on feeding Often located on feeding

appendagesappendages

Most have J – shaped Most have J – shaped gutgut

Often have a grinding Often have a grinding stomach called a stomach called a gastric mill gastric mill

Midgut has digestive Midgut has digestive ceca termed the ceca termed the hepatopancreashepatopancreas

Intestines form and Intestines form and remove wastesremove wastes• Also reclaim waterAlso reclaim water

Anus located at base Anus located at base of telsonof telson

Other Organ SystemsOther Organ Systems Small species don’t require Small species don’t require

complex organ systemscomplex organ systems

HemalHemal• Typical of arthropodsTypical of arthropods• Hemocyanin or hemoglobin Hemocyanin or hemoglobin

dissolved in plasmadissolved in plasma

RespiratoryRespiratory• Gills located in branchial Gills located in branchial

chamberchamber• Inhalant and exhalant Inhalant and exhalant

chamberschambers• Gill bailer (scaphognathite) Gill bailer (scaphognathite)

ventilatesventilates• Many strategies for cleaning Many strategies for cleaning

gills and removing sediment gills and removing sediment from branchial chamberfrom branchial chamber

Excretory systemExcretory system• Paired saccate nephridiaPaired saccate nephridia

Located in segment with 2Located in segment with 2ndnd antennae or 2 antennae or 2ndnd maxillae maxillae Called antennal, maxillary, or green glandsCalled antennal, maxillary, or green glands Nephridiopores open near 2Nephridiopores open near 2ndnd antennae/maxillae antennae/maxillae

Most marine species are osmoconformersMost marine species are osmoconformers

Freshwater species are osmoregulatorsFreshwater species are osmoregulators

Ammonotelic, so nitrogen diffuses across Ammonotelic, so nitrogen diffuses across gillsgills

Nervous system is typical Nervous system is typical of arthropodsof arthropods

• EyesEyes Often compound with as Often compound with as

many as 14,000 ommatidiamany as 14,000 ommatidia Often at the end of a Often at the end of a

movable eyestalk, which movable eyestalk, which greatly increases the field greatly increases the field of viewof view

Some can distinguish colorsSome can distinguish colors

• Many use chromatophores Many use chromatophores to match color of to match color of surroundingssurroundings

• Statocysts and Statocysts and chemosensorschemosensors

Often associated with Often associated with antennaeantennae

Animals frequently clean Animals frequently clean their antennaetheir antennae

ReproductionReproduction All but barnacles are All but barnacles are

gonochoricgonochoric

Usually copulation Usually copulation with internal with internal fertilizationfertilization

Penis or gonopods Penis or gonopods transfer spermtransfer sperm

Appendages such as Appendages such as 22ndnd antennae are antennae are often used to grasp often used to grasp femalefemale

Sometimes males Sometimes males cannot mate with cannot mate with females until after females until after she moltsshe molts

Most brood eggs Most brood eggs attached to attached to appendages or in appendages or in brood chambersbrood chambers

Direct or indirect Direct or indirect (nauplius larva) (nauplius larva) developmentdevelopment

Class AnostracaClass Anostraca

Fairy shrimp and brine shrimp Fairy shrimp and brine shrimp (sea monkeys)(sea monkeys)

Live in ephemeral poolsLive in ephemeral pools• Typically salineTypically saline• Lack fishesLack fishes

15 – 30 mm, but some grow as 15 – 30 mm, but some grow as large as 10 cmlarge as 10 cm

Lack carapaceLack carapace

Sexually dimorphicSexually dimorphic• Males have large 2Males have large 2ndnd antennae antennae

for grasping femalesfor grasping females

Stalked compound eyesStalked compound eyes

Possess setal combs for Possess setal combs for suspension feedingsuspension feeding

Swim upside downSwim upside down

Many tolerate a wide Many tolerate a wide range of salinitiesrange of salinities

Sperm transfer is directSperm transfer is direct• Internal fertilizationInternal fertilization

Class PhyllopodaClass Phyllopoda

800 species800 species

Inhabit freshwater Inhabit freshwater habitats that are habitats that are similar to those of similar to those of anostracansanostracans

Two main typesTwo main types• Large - tadpole Large - tadpole

shrimpsshrimps• Small - water fleasSmall - water fleas

Tadpole ShrimpsTadpole Shrimps TriopsTriops is most famous genus is most famous genus

• Ten species altogetherTen species altogether

Enormous shield-like carapace Enormous shield-like carapace covers most of the animalcovers most of the animal

Most are small, but some reach Most are small, but some reach 10 cm in length10 cm in length

Amazing physiologyAmazing physiology• Dr. Carl Reiber’s lab has Dr. Carl Reiber’s lab has

conducted research using conducted research using Triops Triops as a modelas a model

• Survive in hypoxia and anoxiaSurvive in hypoxia and anoxia Hemoglobin subunit recruitmentHemoglobin subunit recruitment

• Produce two types of eggsProduce two types of eggs Summer eggs- thin shelled and Summer eggs- thin shelled and

hatch rapidlyhatch rapidly Winter eggs - undergo diapauseWinter eggs - undergo diapause

Water FleasWater Fleas Also called cladoceransAlso called cladocerans

• DaphniaDaphnia is most famous genus is most famous genus

Often live in ponds and lakes Often live in ponds and lakes where they make up a large where they make up a large portion of FW zooplankton portion of FW zooplankton communitycommunity

Swim using enlarged 2Swim using enlarged 2ndnd antennae as oarsantennae as oars

Undergo cycles of Undergo cycles of parthenogenesis and parthenogenesis and bisexual reproductionbisexual reproduction

Typically brood eggsTypically brood eggs

Two types of eggs producedTwo types of eggs produced

Undergo cyclomorphosisUndergo cyclomorphosis• Seasonal changes in Seasonal changes in

morphologymorphology• Head shape, spines, neck Head shape, spines, neck

teeth producedteeth produced• Evidence suggests these Evidence suggests these

changes are inducible changes are inducible responses responses

Class MalacostracaClass Malacostraca

Many important Many important orders of crustaceansorders of crustaceans

Crabs, crayfish, and Crabs, crayfish, and shrimpsshrimps

23,000 species23,000 species

Tagmatization is Tagmatization is standardizedstandardized

Order StomatopodaOrder Stomatopoda 300 species of mantis 300 species of mantis

shrimpsshrimps

Predators of fish, crabs, Predators of fish, crabs, shrimps, and molluscsshrimps, and molluscs

Raptorial claws are Raptorial claws are extended and retracted extended and retracted rapidly to capture preyrapidly to capture prey

Best developed Best developed compound eyes of any compound eyes of any crustaceancrustacean• Some even have depth Some even have depth

perceptionperception

5 cm – 36 cm long5 cm – 36 cm long

Can be brightly Can be brightly coloredcolored

Many live in burrowsMany live in burrows

Often pair up with one Often pair up with one mate for lifemate for life

SquillaSquilla is most famous is most famous genusgenus

Order DecapodaOrder Decapoda

10,000 species of 10,000 species of shrimps, shrimps, crayfishes, crayfishes, lobsters, and crabslobsters, and crabs

Important Important ecologically and ecologically and economicallyeconomically

All have 10 legs, All have 10 legs, hence the namehence the name

Shrimp-like DecapodsShrimp-like Decapods

Laterally compressedLaterally compressed

Thin flexible exoskeleton Thin flexible exoskeleton (uncalcified)(uncalcified)

Muscular abdomen that Muscular abdomen that can be used for can be used for escaping (tail flip)escaping (tail flip)

Large pleopods for Large pleopods for swimmingswimming

BenthicBenthic

PenaeusPenaeus is a common is a common genusgenus

Snapping shrimpSnapping shrimp• SynalpheusSynalpheus

• Has one extremely Has one extremely large chelipedlarge cheliped

• One movable finger is One movable finger is cockedcocked

• When released the When released the force generated can force generated can stun prey or crack a stun prey or crack a clam shellclam shell

• Also makes a loud noiseAlso makes a loud noise

Lobster-like DecapodsLobster-like Decapods More dorsoventrally More dorsoventrally

flattenedflattened

Heavier legsHeavier legs

ChelipedsChelipeds

Muscular abdomenMuscular abdomen• Tail flipsTail flips• Small pleopodsSmall pleopods

HomarusHomarus and and ProcambarusProcambarus are famous are famous generagenera

Crab-like DecapodsCrab-like Decapods Most dorsoventrally Most dorsoventrally

compressed of the three compressed of the three groupsgroups

Abdomen is greatly Abdomen is greatly reducedreduced• Hermit crabs have a large Hermit crabs have a large

abdomen that is soft and is abdomen that is soft and is housed in a shellhoused in a shell

• Periodically need to find Periodically need to find larger shellslarger shells

Typically walk sidewaysTypically walk sideways

Some like Some like CallinectesCallinectes can can swimswim

Eggs brooded Eggs brooded between the between the cephalothorax cephalothorax and abdomenand abdomen

Types of crabs:Types of crabs:

• Alaskan kingAlaskan king Probably the Probably the

largest crablargest crab

• Mole crabsMole crabs Lack chelipedsLack chelipeds Burrow in sandBurrow in sand

Japanese spider crabJapanese spider crab• Greatest leg span of any Greatest leg span of any

arthropodarthropod

Decorator crabsDecorator crabs• Have hooked setaeHave hooked setae• Attach things to its Attach things to its

exoskeletonexoskeleton• Aids in protection and Aids in protection and

camouflagecamouflage

Dungeness crabDungeness crab• Cancer magisterCancer magister• Probably the most popular Probably the most popular

food crabfood crab

Freshwater DecapodsFreshwater Decapods Crayfish Crayfish

• The most successful with 400 The most successful with 400 species, worldwidespecies, worldwide

• Many live under stones and Many live under stones and some burrowsome burrow

• ProcambarusProcambarus is an invasive is an invasive species in Western USspecies in Western US

ShrimpsShrimps• Most are tropicalMost are tropical• A few species in the USA few species in the US

CrabsCrabs• Usually must return to the sea Usually must return to the sea

at some point to release larvaeat some point to release larvae• Chinese mitten (or river) crab is Chinese mitten (or river) crab is

an invasive in CAan invasive in CA

Terrestrial CrabsTerrestrial Crabs

Adapted for life on landAdapted for life on land

• Morphological adaptationsMorphological adaptations Gills converted into a Gills converted into a

modified lungmodified lung UricotelicUricotelic

• Behavioral “adaptations”Behavioral “adaptations” Typically live near oceans Typically live near oceans

or in other high humidity or in other high humidity habitatshabitats

Visit water to wet body Visit water to wet body and respiratory surfacesand respiratory surfaces

Typically burrow and are Typically burrow and are nocturnalnocturnal

Some brood embryos on Some brood embryos on land and make mass land and make mass migrations to release migrations to release larvaelarvae

Terrestrial hermit Terrestrial hermit crabs (crabs (CoenobitaCoenobita))

Coconut crabs Coconut crabs ((BirgusBirgus))• Climb trees and Climb trees and

open coconuts, open coconuts, which they eatwhich they eat

• Drink sea waterDrink sea water• Can reach one Can reach one

meter in lengthmeter in length• Some can lift 28 kgSome can lift 28 kg

Christmas Island Christmas Island red crabsred crabs• Make mass Make mass

migrations from migrations from forests to the sea forests to the sea every year to mateevery year to mate

Fiddler crabs are Fiddler crabs are considered semi-considered semi-terrestrialterrestrial

UcaUca lives on sand or mud lives on sand or mud beaches or in mangrove beaches or in mangrove swampsswamps

Emerge from burrows Emerge from burrows when the tide is outwhen the tide is out• ForagingForaging• MatingMating• FightingFighting

Dependent on tide to Dependent on tide to bring new food and bring new food and remove wastesremove wastes

The Decapod Hemal SystemThe Decapod Hemal System Heart is not tubularHeart is not tubular

• Rectangular with three pairs of ostiaRectangular with three pairs of ostia

Well developed vasculatureWell developed vasculature• Seven major arteries leaving heartSeven major arteries leaving heart

McGaw and Reiber have studied many McGaw and Reiber have studied many parameters of decapod circulationparameters of decapod circulation

Circulation takes around 40 sec in large speciesCirculation takes around 40 sec in large species

Hemocyanin transports around 90% of oxygenHemocyanin transports around 90% of oxygen

Neurosecretory Organs of DecapodsNeurosecretory Organs of Decapods

Eyestalks are the most important neurosecretory organsEyestalks are the most important neurosecretory organs

Hormones synthesized in neuron cell bodies of eyestalk Hormones synthesized in neuron cell bodies of eyestalk control:control:• MoltingMolting• ChromatophoresChromatophores• ReproductionReproduction

Sinus gland in eyestalk stores and releases hormones into Sinus gland in eyestalk stores and releases hormones into bloodblood

There are a few endocrine organs outside of nervous There are a few endocrine organs outside of nervous system, but these are under nervous controlsystem, but these are under nervous control• Y-organY-organ

Secretes ecdysoneSecretes ecdysone Located in anterior cephalothoraxLocated in anterior cephalothorax

ChromatophoresChromatophores Located in connective tissue, Located in connective tissue,

deep to the epidermisdeep to the epidermis

Color change is apparent in Color change is apparent in areas where the cuticle is thin areas where the cuticle is thin or transparentor transparent

Used for:Used for:• Thermoregulation – blanching Thermoregulation – blanching

in fiddler crabsin fiddler crabs• Concealment – many shrimps Concealment – many shrimps

change color to match change color to match surroundingssurroundings

Astaxanthin is a carotenoid Astaxanthin is a carotenoid pigment found in decapodspigment found in decapods• Is blue in live animals, because Is blue in live animals, because

it is bound with a proteinit is bound with a protein• Boiling denatures the protein Boiling denatures the protein

and the animal turns redand the animal turns red

Decapod ReproductionDecapod Reproduction

CopulationCopulation• Hermit crabs have to Hermit crabs have to

partially exit shellpartially exit shell

Sperm transfer is Sperm transfer is indirect indirect • Spermatophore extruded Spermatophore extruded

from penes, onto from penes, onto gonopodsgonopods

• Transferred by gonopodsTransferred by gonopods Most anterior pair of Most anterior pair of

pleopods, that are modifiedpleopods, that are modified

Aquatic species attract each other using pheromonesAquatic species attract each other using pheromones• Tactile cues are also importantTactile cues are also important

Visual and sometimes auditory cues are important to Visual and sometimes auditory cues are important to terrestrial speciesterrestrial species• Combat between male fiddler crabs Combat between male fiddler crabs

Egg mass is known as a sponge, and is brooded on Egg mass is known as a sponge, and is brooded on pleopodspleopods

AutotomyAutotomy

Limbs occasionally get Limbs occasionally get autotomized (removed)autotomized (removed)• PredatorsPredators• Self amputationSelf amputation

Little bleedingLittle bleeding

Limb bud formsLimb bud forms• New limb regenerates New limb regenerates

insideinside

Limb bud unfolds during Limb bud unfolds during next moltnext molt• Removing a limb bud Removing a limb bud

delays molting until a delays molting until a new bud forms and limb new bud forms and limb is regeneratedis regenerated

Class Malacostraca, Order EuphausiaceaClass Malacostraca, Order Euphausiacea

85 species of krill85 species of krill

Pelagic, shrimp-like animals found Pelagic, shrimp-like animals found throughout oceansthroughout oceans

Small (about 3 cm long), but found Small (about 3 cm long), but found in enormous densitiesin enormous densities• 60,000 / m60,000 / m33

Chief food for many marine animalsChief food for many marine animals• Blue whale may consume four tons Blue whale may consume four tons

per dayper day

Bioluminescence functions in Bioluminescence functions in schooling and courtship behaviorsschooling and courtship behaviors

Can rapidly molt and leave exuvia Can rapidly molt and leave exuvia behind as decoysbehind as decoys

Order AmphipodaOrder Amphipoda 6000 species of scuds6000 species of scuds

• GammarusGammarus is most famous is most famous genusgenus

Small (5 – 15 mm)Small (5 – 15 mm)• Giant Pacific scuds can Giant Pacific scuds can

reach 28 cm and live 5300 reach 28 cm and live 5300 m deepm deep

Some FW species, and Some FW species, and some semi-terrestrial such some semi-terrestrial such as beach hoppersas beach hoppers• Can leap many times body Can leap many times body

lengthlength

Laterally compressedLaterally compressed

Order IsopodaOrder Isopoda

4000 species 4000 species

Mostly marineMostly marine

Pill bugs (wood lice) are Pill bugs (wood lice) are the most successful the most successful terrestrial crustaceansterrestrial crustaceans

Most are 5 -15 mm, but Most are 5 -15 mm, but the deep sea isopod the deep sea isopod ((BathynomusBathynomus) reaches ) reaches 42 cm42 cm

Dorsoventrally compressedDorsoventrally compressed

Nutritional strategiesNutritional strategies• Some bore into woodSome bore into wood• Some are carnivorousSome are carnivorous• Some parasitize fishesSome parasitize fishes

Have enrollment muscles (pill Have enrollment muscles (pill bugs)bugs)

Terrestrial species specialized Terrestrial species specialized structures to collect water and structures to collect water and channel it to gillschannel it to gills

Class CopepodaClass Copepoda

12,000 species 12,000 species

Most marine, but FW varieties Most marine, but FW varieties dominate zooplankton dominate zooplankton communitiescommunities

Some are parasiticSome are parasitic

Free-living varieties are small (1 - Free-living varieties are small (1 - 17 mm), but some parasites reach 17 mm), but some parasites reach 25 cm25 cm

Long first antennaeLong first antennae• Used by males to grasp femalesUsed by males to grasp females• Usually branch 90Usually branch 90° angles, relative ° angles, relative

to longitudinal axisto longitudinal axis

Possess a median nauplius Possess a median nauplius eyeeye

Form oil droplets for Form oil droplets for buoyancy, which can lead buoyancy, which can lead to petroleum depositsto petroleum deposits

Some undergo DMV of Some undergo DMV of around 300 maround 300 m• One researcher figured out One researcher figured out

that this is the greatest that this is the greatest movement of biomass on movement of biomass on the planetthe planet

Famous genera:Famous genera:• CyclopsCyclops• TisbeTisbe

Swarm on small fish and Swarm on small fish and eat at their finseat at their fins

After fish is immobilized, it After fish is immobilized, it is devouredis devoured

Class CirripediaClass Cirripedia BarnaclesBarnacles

Secrete and inhabit a rigid Secrete and inhabit a rigid calcareous shell that is capable calcareous shell that is capable of growthof growth

Sessile animals that encrust on Sessile animals that encrust on rocks, timber, ships, and even rocks, timber, ships, and even whaleswhales

Fouling ability is amazingFouling ability is amazing• May reduce speed and fuel May reduce speed and fuel

efficiency of a ship by 30%efficiency of a ship by 30%

Abundant intertidally, and may Abundant intertidally, and may be found in distinct patters of be found in distinct patters of zonationzonation• Due to interspecific competitionDue to interspecific competition

Larvae settle and Larvae settle and cements to substrate cements to substrate using glands on its using glands on its headhead• Ventral aspect is upVentral aspect is up• Six pairs of cirri on Six pairs of cirri on

thorax are used for thorax are used for filter feedingfilter feeding

HermaphroditicHermaphroditic• Highly extensible Highly extensible

penis deposits sperm penis deposits sperm in a neighboring in a neighboring barnaclebarnacle

Calcareous shell is Calcareous shell is secreted by exoskeletonsecreted by exoskeleton

There are two pairs of There are two pairs of ventral, movable ventral, movable calcareous plates that form calcareous plates that form an operculuman operculum• Scuta – anterior platesScuta – anterior plates• Terga – posterior platesTerga – posterior plates

Muscles control aperture Muscles control aperture diameterdiameter

Ecdysis occurs but Ecdysis occurs but calcareous shell / plates calcareous shell / plates aren’t shedaren’t shed

Shell is added on to with Shell is added on to with new secretionsnew secretions

DiversityDiversity• Acorn barnaclesAcorn barnacles

BalanusBalanus Those on West coast Those on West coast

of South America of South America can be 23 cm high, 8 can be 23 cm high, 8 cm wide, and are cm wide, and are eaten locally eaten locally

• Stalked barnaclesStalked barnacles Have a peduncle and Have a peduncle and

capitulumcapitulum LepasLepas can grow to can grow to

75 cm in height75 cm in height

Some do not produce shellsSome do not produce shells• Bore into rocksBore into rocks

Others parasitize crabsOthers parasitize crabs• Barnacles alter crab’s behavior, physiology, Barnacles alter crab’s behavior, physiology,

and anatomyand anatomy Molting suppressedMolting suppressed Reproduction suppressed, in fact most are sterilizedReproduction suppressed, in fact most are sterilized Male crabs become feminized and develop a larger Male crabs become feminized and develop a larger

female abdomen, into which barnacle places its own female abdomen, into which barnacle places its own brood pouchbrood pouch

• Betters suits the barnacle’s needsBetters suits the barnacle’s needs

Class OstracodaClass Ostracoda

6000 species of seed 6000 species of seed shrimps that resemble shrimps that resemble miniature clamsminiature clams• Have a bivalved carapaceHave a bivalved carapace

0.25 – 25 mm 0.25 – 25 mm ((GigantocyprisGigantocypris))

Some have cephalic silk Some have cephalic silk glands and spinnerets that glands and spinnerets that secrete silk threads used secrete silk threads used for:for:• DraglinesDraglines• Building shelters for molting Building shelters for molting

Carapace is an Carapace is an extension of headextension of head• Is shed with each moltIs shed with each molt

Some have Some have bioluminescencebioluminescence• Bluish lightBluish light

• Flashed for periods of 1 Flashed for periods of 1 to 2 secondsto 2 seconds

• Used to attract matesUsed to attract mates

Class BranchiuraClass Branchiura 200 species of fish lice200 species of fish lice

Ectoparasites of marine and FW Ectoparasites of marine and FW fishes, and tadpolesfishes, and tadpoles

5 – 30 mm in length5 – 30 mm in length

Structural adaptations for Structural adaptations for attaching to hostattaching to host• First antennae have claws First antennae have claws • Mandibles are toothedMandibles are toothed• First maxillae are suckersFirst maxillae are suckers

Produce digestive enzymes to Produce digestive enzymes to erode host tissue, and feed on erode host tissue, and feed on blood and mucusblood and mucus

Infestations in fish farms can Infestations in fish farms can eradicate entire populationseradicate entire populations