20-1 chapter 20 crustaceans crustaceans. copyright © the mcgraw-hill companies, inc. permission...

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CHAPTER 20CHAPTER 20CHAPTER 20CHAPTER 20

CrustaceansCrustaceans CrustaceansCrustaceans

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

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Sally Lightfoot Crab, from the Galapagos


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OverviewOverview

Over 67,000 living species Over 67,000 living species Insects and crustacea compose Insects and crustacea compose over over

80%80% of all named animal species of all named animal species Divided into 5 classesDivided into 5 classes

We will study 3 classes, Branchiopoda and We will study 3 classes, Branchiopoda and Malacostraca, MaxillopodaMalacostraca, Maxillopoda Branchiopoda = water fleas, brine shrimpBranchiopoda = water fleas, brine shrimp Malacostaca = isopods, krill, crab, lobster, etc.Malacostaca = isopods, krill, crab, lobster, etc. Maxillopoda = barnaclesMaxillopoda = barnacles


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Subphylum CrustaceaSubphylum Crustacea

General Nature of a CrustaceanGeneral Nature of a Crustacean Main distinguishing characteristic of Main distinguishing characteristic of

crustaceans crustaceans Two pairs of antennaeTwo pairs of antennae

Head also has a pair of mandibles and 2 pairs Head also has a pair of mandibles and 2 pairs of maxillaeof maxillae

One pair of appendages on each of the One pair of appendages on each of the additional segmentsadditional segments Some segments may lack appendagesSome segments may lack appendages All appendages, except perhaps first antennae, are All appendages, except perhaps first antennae, are

biramous biramous


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Tagmata (segments) are usually Tagmata (segments) are usually head, thorax, head, thorax, and abdomenand abdomen

In most one or more thoracic segments are In most one or more thoracic segments are fused with the head as a fused with the head as a cephalothoraxcephalothorax

Arrangement of tagmata in Malacostraca is the Arrangement of tagmata in Malacostraca is the ancestral planancestral plan Head has 5 fused somitesHead has 5 fused somites Thorax has 8Thorax has 8 Abdomen has 6Abdomen has 6



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Anterior end is a non-segmented Anterior end is a non-segmented rostrum rostrum (covers eyes in some)(covers eyes in some)

TelsonTelson, with the last abdominal somite and , with the last abdominal somite and uropodsuropods, forms a tail, forms a tail

Dorsal covering is the Dorsal covering is the carapacecarapace May cover most of body or just cephalothoraxMay cover most of body or just cephalothorax



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Form and FunctionForm and Function External FeaturesExternal Features

Secreted cuticle is made of chitin, protein, and Secreted cuticle is made of chitin, protein, and calcareous materialcalcareous material

Heavy plates have more calcareous depositsHeavy plates have more calcareous deposits Joints are soft and thin, allowing flexibilityJoints are soft and thin, allowing flexibility

Telson is not a somiteTelson is not a somite Bears anusBears anus



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Appendages Appendages Most have appendages on each somiteMost have appendages on each somite

Appendages represent Appendages represent homologyhomology Have evolved a wide variety of walking legs, mouthparts, Have evolved a wide variety of walking legs, mouthparts,

swimmerets, etc. from modification of the basic biramous swimmerets, etc. from modification of the basic biramous appendageappendage



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Appendages of crayfish: 3 main parts to each appendageProtopod = brown Endopod = blue Exopod = yellow


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Appendage Function # of pairs

Antenna Touch, taste, equilibrium 2

Mandible Crushing food 1

Maxilla Handling food, drawing water currents to gills

2

Maxilliped Touch, taste, handling food 3

Walking legs Offense, Defense, walking (cheliped is 1st, with pincer)

5

Swimmeret Transfer sperm, create water currents, carrying eggs and young

5

Uropod Swimming, egg protection in females

1

Crawyfish Appendage and Function(Number if pairs)


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Internal FeaturesInternal Features Coelomates - reducedCoelomates - reduced

Persistent blastocoel that becomes filled with Persistent blastocoel that becomes filled with blood blood Hemocoel Hemocoel

Protostomes (mouth first)Protostomes (mouth first) Complete GutComplete Gut



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Muscular SystemMuscular System Striated muscles Striated muscles

Make up a major portion of crustacean Make up a major portion of crustacean bodybody

Most muscles arranged as Most muscles arranged as antagonistic antagonistic groupsgroups FlexorsFlexors draw a limb toward the body and draw a limb toward the body and

extensorsextensors straighten a limb out straighten a limb out Abdominal flexors of a crayfish allow it to Abdominal flexors of a crayfish allow it to

swim backwardswim backward



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Internal Anatomy of the crayfish. Green Gland = Kidney


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Respiratory SystemRespiratory System Smaller crustaceansSmaller crustaceans may exchange gases across thinner areas of cuticle may exchange gases across thinner areas of cuticle Larger crustaceansLarger crustaceans use featherlike gills for gas exchange use featherlike gills for gas exchange

Circulatory Circulatory Open circulatory systemOpen circulatory system

No system of veins to separate blood from interstitial fluidNo system of veins to separate blood from interstitial fluid Hemolymph exits heart through arteries Hemolymph exits heart through arteries Passes to hemocoel to return to the heart via sinusesPasses to hemocoel to return to the heart via sinuses

Dorsal heart Dorsal heart Single-chambered sac of striated muscleSingle-chambered sac of striated muscle

ValvesValves in the arteries prevent backflow in the arteries prevent backflow Hemolymph conducted to gills, if present, for oxygen and carbon dioxide Hemolymph conducted to gills, if present, for oxygen and carbon dioxide

exchangeexchange Hemocyanin and/or hemoglobinHemocyanin and/or hemoglobin are respiratory pigments are respiratory pigments



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Hemolymph travel: Heart, Body, Sinus, Gills, Heart via Ostium (opening)


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Excretory SystemExcretory System Antennal or maxillary glandsAntennal or maxillary glands Called “Called “green glands”green glands” End sac of green gland has a small vesicle and a End sac of green gland has a small vesicle and a

spongy labyrinthspongy labyrinth Labyrinth connects by an excretory tubule to Labyrinth connects by an excretory tubule to

dorsal bladder that opens to exterior poredorsal bladder that opens to exterior pore Hydrostatic pressureHydrostatic pressure within a hemocoel provides within a hemocoel provides

a force for filtration of fluid into the end saca force for filtration of fluid into the end sac



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Nervous and Sensory Systems Nervous and Sensory Systems More fused gangliaMore fused ganglia than in other arthropods than in other arthropods Pair of ganglia connects to eyes and two pairs of Pair of ganglia connects to eyes and two pairs of

antennaeantennae Nerves join this brain to the mouth, appendages, Nerves join this brain to the mouth, appendages,

esophagus, and antennal glandsesophagus, and antennal glands Ventral nerve cordVentral nerve cord has a pair of ganglia for each has a pair of ganglia for each

somite to control appendagessomite to control appendages Tactile hairsTactile hairs occur on the body, especially on occur on the body, especially on

chelae, mouthparts and telsonchelae, mouthparts and telson Chemical sensing of taste and smell occurs in hairs Chemical sensing of taste and smell occurs in hairs

on antennae and mouthon antennae and mouth Compound eye migrates pigments for day or night Compound eye migrates pigments for day or night

visionvision



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Compound eyes work differently during day and night. Pigment cells will expand or constrict to allow different amounts of light to hit the photoreceptor cells


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Reproduction, Life Cycles, and Endocrine Reproduction, Life Cycles, and Endocrine Function Function Diversity of ReproductionDiversity of Reproduction

Most crustaceansMost crustaceans group eggs in brood group eggs in brood chambers, in brood sacs attached to the chambers, in brood sacs attached to the abdomen, or attached to abdominal abdomen, or attached to abdominal appendagesappendages

Crayfishes Crayfishes develop directly without a larval develop directly without a larval formform



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Most crustaceansMost crustaceans have a larva unlike the adult have a larva unlike the adult in form, and undergo metamorphosisin form, and undergo metamorphosis

The The nauplius nauplius is a common larval form is a common larval form Appendages and somites are added in a Appendages and somites are added in a

series of moltsseries of molts Metamorphosis of a Metamorphosis of a barnaclebarnacle proceeds from a proceeds from a

free-swimming nauplius to a larva with a free-swimming nauplius to a larva with a bivalve carapace and finally to a sessile adult bivalve carapace and finally to a sessile adult with plateswith plates



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Life cycle of a Gulf ShrimpMetamorphosis


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Ecdysis Ecdysis Necessary for a crustacean to increase in size the Necessary for a crustacean to increase in size the

Exoskeleton does not growExoskeleton does not grow Physiology of molting affects reproduction, Physiology of molting affects reproduction,

behavior, and many metabolic processesbehavior, and many metabolic processes Underlying Underlying epidermisepidermis secretes cuticle secretes cuticle Outermost Outermost epicuticleepicuticle and 2 layer and 2 layer procuticle procuticle

dissolve and are discarded.dissolve and are discarded.



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Pre-molt Stage:Protocuticle sperates from epidermis.

Epidermis secretes new epicuticle.

Pre-molt Continued:Molting fluid dissolves endocuticle, and

Solutions are rebsorbed.New exocuticle develops

Ecdysis Stage:Old epicuticle and exocuticle are discarded.

Post-ecdysis:New cuticle is stretched and hardens.

Endocuticle is secreted.


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A. Membrane between carapace and abdomen ruptures (2 hours)B. Head Thorax and Abdomen withdraw (15 minutes)

C. Lobster continues rapid absorption of water to increase length by 20% and weight by 50%. Tissue water will be replaced by protein later. (weeks)

Lobster Molt


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Hormonal Control of Ecdysis Hormonal Control of Ecdysis Temperature, day length, or other stimuli trigger Temperature, day length, or other stimuli trigger

central nervous system to begin ecdysiscentral nervous system to begin ecdysis Central nervous system decreases production of Central nervous system decreases production of

molt-inhibitingmolt-inhibiting hormone by the medulla region of hormone by the medulla region of the brainthe brain

Promotes release of molting hormone from the Promotes release of molting hormone from the glands near mandible which promotes ecdysis glands near mandible which promotes ecdysis



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Feeding Habits Feeding Habits Suspension feeders generate water Suspension feeders generate water

currents in order to feed on plankton, currents in order to feed on plankton, detritus ,and bacteriadetritus ,and bacteria

Predators consume larvae, worms, Predators consume larvae, worms, crustaceans, snails, and fishescrustaceans, snails, and fishes

Scavengers eat dead animal and plant Scavengers eat dead animal and plant mattermatter

Crayfishes have a two-part stomachCrayfishes have a two-part stomach Gastric mill grinds up food in 1Gastric mill grinds up food in 1stst compartment compartment



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Diplopoda have a 2 part stomach: Cardiac and PyloricContain teeth for mastication and setae for straining


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Class BranchiopodaClass Branchiopoda Over 10,000 species, 4 ordersOver 10,000 species, 4 orders

Order Anostraca,Order Anostraca, includes fairy shrimp and includes fairy shrimp and brine shrimp brine shrimp Lack a carapace Lack a carapace

Order Cladocera,Order Cladocera, includes water fleas includes water fleas (daphnia) (daphnia) Carapace encloses the body but not the head Carapace encloses the body but not the head

Brief Survey of CrustaceansBrief Survey of Crustaceans


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In all, In all, legslegs serve as respiratory organs, assist serve as respiratory organs, assist in suspension feeding, and locomotion in suspension feeding, and locomotion

Most are freshwater Most are freshwater Important component of Important component of freshwater freshwater

zooplanktonzooplankton May reproduce by parthenogenesis to May reproduce by parthenogenesis to rapidly rapidly

boost summer populationsboost summer populations and then by and then by sexual reproduction with the onset of sexual reproduction with the onset of unfavorable conditionsunfavorable conditions

Fertilized eggs highly Fertilized eggs highly resistant to coldresistant to cold Critical for winter survival of populationCritical for winter survival of population



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Class MaxillopodaClass Maxillopoda General body planGeneral body plan

No appendagesNo appendages on abdomen on abdomen Subclass Cirripedia - Subclass Cirripedia - barnaclesbarnacles



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Subclass CirripediaSubclass Cirripedia Includes barnacles and three orders of Includes barnacles and three orders of

burrowing or parasitic formsburrowing or parasitic forms Adults are Adults are sessilesessile and attach directly (acorn and attach directly (acorn

barnacles) or by a stalk (goose barnacles)barnacles) or by a stalk (goose barnacles) Carapace surrounds body and secretes a set Carapace surrounds body and secretes a set

of calcareous platesof calcareous plates Head is reduced, abdomen is absentHead is reduced, abdomen is absent Jointed feeding legs bear setae and extend Jointed feeding legs bear setae and extend

from the plates to feed on small particlesfrom the plates to feed on small particles



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A. Acorn Barnacle B. Gooseneck Barnacle


Barnacles on healthy grey whale Contains commensalistic barnacles

And parasitic amphipods (arrows)


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Life cycle of parasitic barnacle.Enters crab, root-like processes grow throughout body.

Reproductive structure develops externally.


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Class MalacostracaClass Malacostraca Largest and most diverse classLargest and most diverse class of Crustacea with over 20,000 of Crustacea with over 20,000

species species Contains three subclasses, 14 orders, and many subordersContains three subclasses, 14 orders, and many suborders

Order IsopodaOrder Isopoda Only Only truly terrestrialtruly terrestrial crustaceans crustaceans Also have marine and freshwater formsAlso have marine and freshwater forms Dorsoventrally flattened, lack a carapace, and have sessile Dorsoventrally flattened, lack a carapace, and have sessile

compound eyescompound eyes Common land forms include Common land forms include sow bugs and pill bugssow bugs and pill bugs Some isopods are highly modified as parasites of fishes or Some isopods are highly modified as parasites of fishes or

crustaceanscrustaceans



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A. Pill BugsB. Freshwater Sow bug - aquatic isopod


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Isopod Parasite


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Order Euphausiacea Order Euphausiacea Approximately 90 species Approximately 90 species Includes important ocean plankton Includes important ocean plankton

called called krillkrill



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Order DecapodaOrder Decapoda 5 pairs of walking legs 5 pairs of walking legs In crabs, first pair of walking legs form In crabs, first pair of walking legs form

pincers (Chelipeds)pincers (Chelipeds) Approximately 18,000 species Approximately 18,000 species Includes crayfishes, lobsters, crabs, and Includes crayfishes, lobsters, crabs, and

true shrimp (size of cephalothorax and true shrimp (size of cephalothorax and abdomen vary)abdomen vary)



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A. Tropical Rock CrabB. Hermit CrabC. Male Fiddler CrabD. Red Night ShrimpE. Spiny Lobster


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Sponge Crab - masks itself with materials from environment, sponge

20-1 chapter 20 crustaceans crustaceans. copyright © the mcgraw-hill companies, inc. permission...

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pairs of antennae head

biramous slide

abdomen tagmata segments

pair of appendages

additional segments

thoracic segments

pairs of maxillae head