Transcript Phylum Arthropoda Subphylum Crustacea

Where are we?
Ecdysozoa
Deuterostomia
Lophotrochozoa
Nematoda
Arthropoda
Tardigrada
Onychophora
Annelida
Mollusca
Platyhelminthes
Phylum Arthropoda
Subphylum Crustacea
Crustacea
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Terrestrial and aquatic
All depths in marine, brackish, and
freshwater
> 67,000 described species, likely 5-10x
that number no yet described
Diverse form, size, and habitat
5 classes, 34 orders
Characteristics
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Head = 5 segments, trunk divided into
thorax and abdomen
Carapace or cephalic shield
Appendages multi-articulate; either
uniramous or biramous
Mandibles are modified limbs that function
as jaws
Gas exchange by diffusion across
specialized surfaces
Characteristics
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Excretion by nephridia
Simple and compound eyes in at least one
life cycle stage
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Compound eyes on stalk
Gut with digestive cecae
Nauplius larvae, either mixed or direct
development
2 pairs of antennae
Crustacean Bauplan
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Thorax
 anterior
segments fused = cephalon
 Maxillipeds:
additional mouthparts
 Number of segments in thorax varies
 Thorax appendages = pereopods
swimming, walking, gas exchange, feeding,
defense
 ultiarticulate and biramous
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Basic Crustacean Bauplan
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Abdomen
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Segments
Number of segments used in ID
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Appendages = pleopods
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Biramous, flap-like
swimming
Culminate in telson
Anus
 caudal rami
 w/uropods (last pair of abdominal appendages) forms
tail fan
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Adult Crustacean
Crustacean Bauplan
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Nauplius Larvae
Single, median, simple eye
 3 pairs of sectioned, functional limbs
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Become antennules, antennae, and mandibles
Diagrams
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adult Crustacean diagram:
http://www.enchantedlearning.com/subject
s/invertebrates/crustacean/index.shtml
Circulation
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Open circulatory system
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Dorsal ostiate heart
Internal organs bathed in fluid
Simple heart and vessels in most
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Sessile species no heart; pumping vessels
Blood
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Variety of cell types
Dissolved hemoglobin or hemocyanin
 Explosive cells release a clotting agent at injury sites
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Heart Shape
Heart long and tubular; to
postcephalic region
 Or, globular, box shape, in thorax;
association with thoracic gills
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Gas Exchange
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Aquatic
Small organisms = diffusion
 Concealed gills for protection, prevent
dessication
 External gills
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Modified thoracic limbs
 Gills are thin; maximize gas exchange
 Most species beat gills to maintain flow
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Gas Exchange
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Terrestrial
 Cutaneous Respiration
 Membranes on legs of some species
 Gills
 Concealed
 Pseudotrachea
 Internal blind sacs to outside through small pores
 Air in sacs, gas exchange with blood
 Internal gills moist
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Water currents
Hydraulic vacuum
Filter feeding
Feeding basket
Passive
Twirling antennae
Direct manipulation
Sand grazers or Sand lickers
Predators
Parasitism
Water Currents
Thoracic limbs for swimming and creating
suspension feeding currents
 Water drawn into space
 Particles trapped by setae
 moved to food groove and toward head
Hydraulic vacuum
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Mouth appendages = paddles
Water containing food drawn into interlimb
space
Food particles are not filtered, but captured in
small parcels of water
Individual algal cells are captured this way
Filter feeding
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Sessile crustaceans have feathery cirri to filter
feed
food up to one mm
= detritus, bacteria, algae and various
zooplankton
Some can coil cirrus around large prey in a
tentacle fashion
Filter feeding in slow water
Extend pairs of cirri like a fan
 Sweep rhythmically through water
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Filter feeding in fast water
Allow water to run through filter
 video
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Passive feeding
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Use cirri to passively strain
Burrow into sand with anterior facing
upward
Extend cirri to capture bacteria, protists
and phytoplankton
Antennae brush food towards mouth
Twirl antennae
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Create spiraling currents that bring food
toward mouth
Food entangled in setae near base of
mouth, brushed in
Direct manipulation
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Manipulation by mouthparts, pereopods
and subchelate anterior legs
Sand grazers or Sand lickers
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Brush sand grains with setose mouthparts
Select individual sand grain, rotate and
tumble against mouthparts to remove
organic material
Predator
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Grab prey with chelae pereopods
Tear, grind and shear with mouthparts
Hunters or ambushers use raptorial
subchelae to stab, club or smash prey
Some hold prey in cage using endopods;
others inject and suck out tissues
Snapping Shrimp
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Use large cheliped to snap close:
produces loud popping sound and “shock”
wave
Pressure wave stuns prey, pull into burrow
Snapping Shrimp Video
http://www.sciencemag.org/feature/data/1052273files/video.shl
Digestive system
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Foregut
 Lined with cuticle that is continuous with
exoskeleton, molted
 Short pharynx-esophagus, stomach
 Stomach = chambers for storage,
grinding and sorting
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Midgut
 intestine
 Length varies with body shape and
size, diet
 digestive ceca
 Hindgut
 Short,
to anus
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Foregut functions
transport food to midgut and/or processing by
chemical digestion
 cardiac stomach = storage, bits are moved
past gastric mill (sclerotized teeth for grinding)
 pyloric stomach = filter large particles
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midgut, hindgut and anus
Excretion and Osmoregulation
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Ammonia by nephridia and gills
nephridial excretory organs as antennal
glands (green glands) or maxillary glands
Inner blind end is coelomic remnant of
nephridium = sacculus
Sacculus
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Actively remove and secrete material from
blood into excretory lumen
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metabolic waste removal and water and
ion balance
Other osmoregulation
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Thin areas of cuticle
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Gill surfaces
terrestrial isopods: ammonia diffuses from
the body as gas
Nervous System and Sense Organs
CNS
 Brain: three fused ganglia
Protocerebrum
Deutocerebrum
Tritocerebrum
 Primitive nervous system = ladderlike
Nervous System and Sense Organs
variety of sensory receptors
 innervated setae or sensilla: contain
mechanoreceptors and chemoreceptors
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Propioceptors
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Animals in Class Malacostraca: statocysts
Nervous System and Sense Organs
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Two rhabdomeric photoreceptors:
Median simple eyes
Lateral compound eyes
Most possess both, either simultaneously
or during development
Naupliar eye = primitive, secondarily lost
Nervous System and Sense Organs
Lateral compound eyes
 Lack visual acuity
 Discern shapes, patterns and movement
 Color vision in some
 Lacking in many taxa
Nervous System and Sense Organs
Underwater vision
 Problems with angular distribution of light, lower
intensity, and narrow range of wavelengths than
in air
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Solution: Mount eyes on stalks, increase
information available to eyes. Increases field of
view, and binocular range
Nervous System and Sense Organs
Complex Endocrine and Neurosecretory
Systems
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Not well known
Molting, chromatophore activity, and
reproduction under hormonal and
neurosecretory control
Bioluminescence in several groups
Reproduction And Development
Reproduction
 Exploit virtually every life history scheme
imaginable
 Usually dioecious
 Hermaphroditism in remipedes,
cephalocarids, cirripedes, few decapods
 Parthenogenesis common among
branchiopods and certain ostracods
Reproduction And Development
Reproduction Systems
 Gonads paired structures in trunk
 Pair of gonoducts from gonads to genital
pores on trunk segment
 Male pair of penes, or single fused median
penis
 Female include seminal receptacles
Reproduction And Development
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Most crustacea copulate
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courtship behavior
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Pairing more or less permanent, or seasonal
Reproduction And Development
Fiddler crab example
Males use cheliped waving to attract females, repel
competing males
Males produce sounds by stridulation, substratum
thumping to attract mates
Mating when male entices female into burrow
Reproduction And Development
Reproductive systems continued
 Sperm transferred either loose in seminal
fluid or packaged in spermatophores
 Sperm deposited directly into oviduct or
into seminal receptacle
 Sperm can be stored for long periods