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Biology 320 Invertebrate Zoology Fall 2005


Biology 320 Invertebrate Zoology Fall 2005 Chapter 19 Phylum Arthropoda, Subphylum Crustacea Introduction to Crustaceans 42,000 species Crabs, shrimps, lobsters ... – PowerPoint PPT presentation

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Title: Biology 320 Invertebrate Zoology Fall 2005

Biology 320Invertebrate ZoologyFall 2005
  • Chapter 19 Phylum Arthropoda,
  • Subphylum Crustacea

Introduction to Crustaceans
  • 42,000 species
  • Crabs, shrimps, lobsters, and barnacles
  • Important ecologically
  • Zooplankton
  • Mainly marine, but some FW and a few terrestrial
  • Mandibulates, along with myriapods and insects
  • Two pairs of antennae

Body Form
  • Two tagma in most
  • Two pairs of antennae
  • 1st and 2nd antennae
  • Mandibles
  • Two pairs of maxillae
  • 1st and 2nd maxillae
  • Lateral compound eyes
  • Often on eyestalks

  • Pereopods
  • Walking legs
  • Pleopods
  • Swimmerets
  • Uropods
  • Make up tail fin
  • Exoskeleton typically mineralized
  • Calcified

Nutrition and Digestive System
  • Many strategies feed on suspended particles,
    detritus, carrion, plants and/or animals
  • Possess several mouthparts
  • Usually have gnathobases
  • Coxae of appendages forms a food groove
  • Many use a structure called a setal comb to
    filter feed
  • Often located on feeding appendages

  • Most have J shaped gut
  • Often have a grinding stomach called a gastric
  • Midgut has digestive ceca termed the
  • Intestines form and remove wastes
  • Also reclaim water
  • Anus located at base of telson

Other Organ Systems
  • Small species dont require complex organ systems
  • Hemal
  • Typical of arthropods
  • Hemocyanin or hemoglobin dissolved in plasma
  • Respiratory
  • Gills located in branchial chamber
  • Inhalant and exhalant chambers
  • Gill bailer (scaphognathite) ventilates
  • Many strategies for cleaning gills and removing
    sediment from branchial chamber

  • Excretory system
  • Paired saccate nephridia
  • Located in segment with 2nd antennae or 2nd
  • Called antennal, maxillary, or green glands
  • Nephridiopores open near 2nd antennae/maxillae
  • Most marine species are osmoconformers
  • Freshwater species are osmoregulators
  • Ammonotelic, so nitrogen diffuses across gills

  • Nervous system is typical of arthropods
  • Eyes
  • Often compound with as many as 14,000 ommatidia
  • Often at the end of a movable eyestalk, which
    greatly increases the field of view
  • Some can distinguish colors
  • Many use chromatophores to match color of
  • Statocysts and chemosensors
  • Often associated with antennae
  • Animals frequently clean their antennae

  • All but barnacles are gonochoric
  • Usually copulation with internal fertilization
  • Penis or gonopods transfer sperm
  • Appendages such as 2nd antennae are often used to
    grasp female

  • Sometimes males cannot mate with females until
    after she molts
  • Most brood eggs attached to appendages or in
    brood chambers
  • Direct or indirect (nauplius larva) development

Class Anostraca
  • Fairy shrimp and brine shrimp (sea monkeys)
  • Live in ephemeral pools
  • Typically saline
  • Lack fishes
  • 15 30 mm, but some grow as large as 10 cm
  • Lack carapace
  • Sexually dimorphic
  • Males have large 2nd antennae for grasping females

  • Stalked compound eyes
  • Possess setal combs for suspension feeding
  • Swim upside down
  • Many tolerate a wide range of salinities
  • Sperm transfer is direct
  • Internal fertilization

Class Phyllopoda
  • 800 species
  • Inhabit freshwater habitats that are similar to
    those of anostracans
  • Two main types
  • Large - tadpole shrimps
  • Small - water fleas

Tadpole Shrimps
  • Triops is most famous genus
  • Ten species altogether
  • Enormous shield-like carapace covers most of the
  • Most are small, but some reach 10 cm in length
  • Amazing physiology
  • Dr. Carl Reibers lab has conducted research
    using Triops as a model
  • Survive in hypoxia and anoxia
  • Hemoglobin subunit recruitment
  • Produce two types of eggs
  • Summer eggs- thin shelled and hatch rapidly
  • Winter eggs - undergo diapause

Water Fleas
  • Also called cladocerans
  • Daphnia is most famous genus
  • Often live in ponds and lakes where they make up
    a large portion of FW zooplankton community
  • Swim using enlarged 2nd antennae as oars
  • Undergo cycles of parthenogenesis and bisexual

  • Typically brood eggs
  • Two types of eggs produced
  • Undergo cyclomorphosis
  • Seasonal changes in morphology
  • Head shape, spines, neck teeth produced
  • Evidence suggests these changes are inducible

Class Malacostraca
  • Many important orders of crustaceans
  • Crabs, crayfish, and shrimps
  • 23,000 species
  • Tagmatization is standardized

Order Stomatopoda
  • 300 species of mantis shrimps
  • Predators of fish, crabs, shrimps, and molluscs
  • Raptorial claws are extended and retracted
    rapidly to capture prey
  • Best developed compound eyes of any crustacean
  • Some even have depth perception

  • 5 cm 36 cm long
  • Can be brightly colored
  • Many live in burrows
  • Often pair up with one mate for life
  • Squilla is most famous genus

Order Decapoda
  • 10,000 species of shrimps, crayfishes, lobsters,
    and crabs
  • Important ecologically and economically
  • All have 10 legs, hence the name

Shrimp-like Decapods
  • Laterally compressed
  • Thin flexible exoskeleton (uncalcified)
  • Muscular abdomen that can be used for escaping
    (tail flip)
  • Large pleopods for swimming
  • Benthic

  • Penaeus is a common genus
  • Snapping shrimp
  • Synalpheus
  • Has one extremely large cheliped
  • One movable finger is cocked
  • When released the force generated can stun prey
    or crack a clam shell
  • Also makes a loud noise

Lobster-like Decapods
  • More dorsoventrally flattened
  • Heavier legs
  • Chelipeds
  • Muscular abdomen
  • Tail flips
  • Small pleopods
  • Homarus and Procambarus are famous genera

Crab-like Decapods
  • Most dorsoventrally compressed of the three
  • Abdomen is greatly reduced
  • Hermit crabs have a large abdomen that is soft
    and is housed in a shell
  • Periodically need to find larger shells
  • Typically walk sideways
  • Some like Callinectes can swim

  • Eggs brooded between the cephalothorax and
  • Types of crabs
  • Alaskan king
  • Probably the largest crab
  • Mole crabs
  • Lack chelipeds
  • Burrow in sand

  • Japanese spider crab
  • Greatest leg span of any arthropod
  • Decorator crabs
  • Have hooked setae
  • Attach things to its exoskeleton
  • Aids in protection and camouflage
  • Dungeness crab
  • Cancer magister
  • Probably the most popular food crab

Freshwater Decapods
  • Crayfish
  • The most successful with 400 species, worldwide
  • Many live under stones and some burrow
  • Procambarus is an invasive species in Western US
  • Shrimps
  • Most are tropical
  • A few species in the US
  • Crabs
  • Usually must return to the sea at some point to
    release larvae
  • Chinese mitten (or river) crab is an invasive in

Terrestrial Crabs
  • Adapted for life on land
  • Morphological adaptations
  • Gills converted into a modified lung
  • Uricotelic
  • Behavioral adaptations
  • Typically live near oceans or in other high
    humidity habitats
  • Visit water to wet body and respiratory surfaces
  • Typically burrow and are nocturnal
  • Some brood embryos on land and make mass
    migrations to release larvae

  • Terrestrial hermit crabs (Coenobita)
  • Coconut crabs (Birgus)
  • Climb trees and open coconuts, which they eat
  • Drink sea water
  • Can reach one meter in length
  • Some can lift 28 kg
  • Christmas Island red crabs
  • Make mass migrations from forests to the sea
    every year to mate

  • Fiddler crabs are considered semi-terrestrial
  • Uca lives on sand or mud beaches or in mangrove
  • Emerge from burrows when the tide is out
  • Foraging
  • Mating
  • Fighting
  • Dependent on tide to bring new food and remove

(No Transcript)
The Decapod Hemal System
  • Heart is not tubular
  • Rectangular with three pairs of ostia
  • Well developed vasculature
  • Seven major arteries leaving heart
  • McGaw and Reiber have studied many parameters of
    decapod circulation
  • Circulation takes around 40 sec in large species
  • Hemocyanin transports around 90 of oxygen

Neurosecretory Organs of Decapods
  • Eyestalks are the most important neurosecretory
  • Hormones synthesized in neuron cell bodies of
    eyestalk control
  • Molting
  • Chromatophores
  • Reproduction
  • Sinus gland in eyestalk stores and releases
    hormones into blood
  • There are a few endocrine organs outside of
    nervous system, but these are under nervous
  • Y-organ
  • Secretes ecdysone
  • Located in anterior cephalothorax

  • Located in connective tissue, deep to the
  • Color change is apparent in areas where the
    cuticle is thin or transparent
  • Used for
  • Thermoregulation blanching in fiddler crabs
  • Concealment many shrimps change color to match
  • Astaxanthin is a carotenoid pigment found in
  • Is blue in live animals, because it is bound with
    a protein
  • Boiling denatures the protein and the animal
    turns red

Decapod Reproduction
  • Copulation
  • Hermit crabs have to partially exit shell
  • Sperm transfer is indirect
  • Spermatophore extruded from penes, onto gonopods
  • Transferred by gonopods
  • Most anterior pair of pleopods, that are modified

  • Aquatic species attract each other using
  • Tactile cues are also important
  • Visual and sometimes auditory cues are important
    to terrestrial species
  • Combat between male fiddler crabs
  • Egg mass is known as a sponge, and is brooded on

  • Limbs occasionally get autotomized (removed)
  • Predators
  • Self amputation
  • Little bleeding
  • Limb bud forms
  • New limb regenerates inside
  • Limb bud unfolds during next molt
  • Removing a limb bud delays molting until a new
    bud forms and limb is regenerated

Class Malacostraca, Order Euphausiacea
  • 85 species of krill
  • Pelagic, shrimp-like animals found throughout
  • Small (about 3 cm long), but found in enormous
  • 60,000 / m3
  • Chief food for many marine animals
  • Blue whale may consume four tons per day
  • Bioluminescence functions in schooling and
    courtship behaviors
  • Can rapidly molt and leave exuvia behind as decoys

Order Amphipoda
  • 6000 species of scuds
  • Gammarus is most famous genus
  • Small (5 15 mm)
  • Giant Pacific scuds can reach 28 cm and live 5300
    m deep
  • Some FW species, and some semi-terrestrial such
    as beach hoppers
  • Can leap many times body length
  • Laterally compressed

Order Isopoda
  • 4000 species
  • Mostly marine
  • Pill bugs (wood lice) are the most successful
    terrestrial crustaceans
  • Most are 5 -15 mm, but the deep sea isopod
    (Bathynomus) reaches 42 cm

  • Dorsoventrally compressed
  • Nutritional strategies
  • Some bore into wood
  • Some are carnivorous
  • Some parasitize fishes
  • Have enrollment muscles (pill bugs)
  • Terrestrial species specialized structures to
    collect water and channel it to gills

Class Copepoda
  • 12,000 species
  • Most marine, but FW varieties dominate
    zooplankton communities
  • Some are parasitic
  • Free-living varieties are small (1 - 17 mm), but
    some parasites reach 25 cm
  • Long first antennae
  • Used by males to grasp females
  • Usually branch 90 angles, relative to
    longitudinal axis

  • Possess a median nauplius eye
  • Form oil droplets for buoyancy, which can lead to
    petroleum deposits
  • Some undergo DMV of around 300 m
  • One researcher figured out that this is the
    greatest movement of biomass on the planet
  • Famous genera
  • Cyclops
  • Tisbe
  • Swarm on small fish and eat at their fins
  • After fish is immobilized, it is devoured

Class Cirripedia
  • Barnacles
  • Secrete and inhabit a rigid calcareous shell that
    is capable of growth
  • Sessile animals that encrust on rocks, timber,
    ships, and even whales
  • Fouling ability is amazing
  • May reduce speed and fuel efficiency of a ship by
  • Abundant intertidally, and may be found in
    distinct patters of zonation
  • Due to interspecific competition

  • Larvae settle and cements to substrate using
    glands on its head
  • Ventral aspect is up
  • Six pairs of cirri on thorax are used for filter
  • Hermaphroditic
  • Highly extensible penis deposits sperm in a
    neighboring barnacle

  • Calcareous shell is secreted by exoskeleton
  • There are two pairs of ventral, movable
    calcareous plates that form an operculum
  • Scuta anterior plates
  • Terga posterior plates
  • Muscles control aperture diameter
  • Ecdysis occurs but calcareous shell / plates
    arent shed
  • Shell is added on to with new secretions

  • Diversity
  • Acorn barnacles
  • Balanus
  • Those on West coast of South America can be 23 cm
    high, 8 cm wide, and are eaten locally
  • Stalked barnacles
  • Have a peduncle and capitulum
  • Lepas can grow to 75 cm in height

  • Some do not produce shells
  • Bore into rocks
  • Others parasitize crabs
  • Barnacles alter crabs behavior, physiology, and
  • Molting suppressed
  • Reproduction suppressed, in fact most are
  • Male crabs become feminized and develop a larger
    female abdomen, into which barnacle places its
    own brood pouch
  • Betters suits the barnacles needs

Class Ostracoda
  • 6000 species of seed shrimps that resemble
    miniature clams
  • Have a bivalved carapace
  • 0.25 25 mm (Gigantocypris)
  • Some have cephalic silk glands and spinnerets
    that secrete silk threads used for
  • Draglines
  • Building shelters for molting

  • Carapace is an extension of head
  • Is shed with each molt
  • Some have bioluminescence
  • Bluish light
  • Flashed for periods of 1 to 2 seconds
  • Used to attract mates

Class Branchiura
  • 200 species of fish lice
  • Ectoparasites of marine and FW fishes, and
  • 5 30 mm in length
  • Structural adaptations for attaching to host
  • First antennae have claws
  • Mandibles are toothed
  • First maxillae are suckers
  • Produce digestive enzymes to erode host tissue,
    and feed on blood and mucus
  • Infestations in fish farms can eradicate entire
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