Invertebrate Zoology
Lecture 17: Phylum Arthropoda, Part 2
Subphylum Crustacea
Focus: Marine Crustacea
Lecture outline
 Subphylum Crustacea
Overview
Selected groups
Key Crustacean features



Two pairs of antennae; 3 pairs of
mouthparts (mandibles, 2 prs maxillae)
Compound eyes, sometimes on stalks
Body regions:
 Head and thorax often  "cephalothorax“
 Abdomen



Biramous appendages: thoracic &
abdominal
Calcium carbonate in cuticle
Many have gills
Crustacea diversity: overview
 Differences in tagmatization
 Differences in appendage structure &
function
Is the Class Remepedia truly “primitive?”
Class Malacostraca
(Subclass Eumalacostraca)
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
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Five-segmented head
Eight-segmented thorax
Six-segmented abdomen
“Tail” = telson + uropods
Carapace: partly/completely covers head &
thorax
Class Malacostraca
 Thoracic appendages = thoracopods
Maxilloped
Cheliped
Pereopod
 Abdominal appendages
Pleopod
Class Malacostraca
 Order Euphausiacea: krill!
Class Malacostraca
 Order Euphausiacea: krill!
Pelagic; schooling
Key food resource in marine food
webs
Pereopods  feeding basket
 Compression-filtration
Pleopods: swimming
Ancestral to Decapoda?
Class Malacostraca

Order Decapoda
 T1 – T3 = maxillopeds
 T4-T8 for grasping & movement

T4 often is chelate (claw-like)
 Gills: base of thoracic appendages
 Cephalothorax covered by carapace
 Stalked eyes
Class Malacostraca

Order Decapoda: Infraorder Caridea
 Shrimp
 “Classic” Decapoda features


Most similar to early Decapoda?
Compare to Euphausiacea
Class Malacostraca

Order Decapoda: Infraorder Caridea
 Variety of local species
 Oregon pink shrimp!


Protandrous hermaphrodites
Sustainable fishery (rare)
 Cleaner shrimp
 Bay shrimp
Class Malacostraca

Order Decapoda:
Infraorder Palinura
 Spiny lobsters



Similar to Caridea
Common in S.
California
Lack powerful
cheliped
 Protection?
 Group molting
Class Malacostraca

Order Decapoda:
Infraorder Anomura
 T4 chelate
 Reduction of T8 &
sometimes T7
 Abdomen not key in
movement


Pleopod reduction
Asymmetrical or
tucked
Class Malacostraca

Order Decapoda:
Infraorder Anomura
 Hermit crabs
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
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Role of reduced T7, T8
Asymmetry
Acquiring shells
Students.washington.edu
Class Malacostraca

Order Decapoda:
Infraorder Anomura
 Porcelain crabs
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Role of reduced T8
Role of abdomen
Filter feeding
Other behaviors and
oddities
Class Malacostraca

Order Decapoda:
Infraorder Anomura
 Mole crabs


Thoracopods
specialized for
“paddling” sand
Why doesn’t it
suffocate when
buried?
Class Malacostraca

Order Decapoda: Infraorder Brachyura
 True crabs


T4-T8 well-developed; T4 chelate
Reduced abdomen
 Adaptive value?
Shore crabs
Hemigrapsus nudus
Pachygrapsus crassipes
Hemigrapsus oregonensis
Cancer sp. crabs
C. antennarius
C. magister
C. productus
C. oregonensis
Pugettia producta: shield-backed
kelp crab
Reproduction: Cancer spp.
Reproduction
Class Malacostraca
Subclass Eumalacostraca
 Order Stomatopoda: mantis shrimps
Class Malacostraca
Subclass Eumalacostraca
 Order Stomatopoda: mantis shrimps
Predatory; burrow dwellers
Second thoracopod = raptorial
 Slicer/stabbers
 Smashers
Gills associated with abdominal appendages
Coloration
 threat displays
 mate attraction
Class Malacostraca
Order Amphipoda
Class Malacostraca
Order Amphipoda
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
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Laterally
compressed
Cephalon: head
plus first thoracic
segment
Non-stalked eyes;
compound
Thoracic brood
pouch
 Beachhopper
appendages
Gnathopods
Some modified for
jumping
Pleopods
 Movement; respiration
Caprellid with thoracic brood pouch
Class Malacostraca
Order Isopoda
Idotea sp.
Ligiapallasii
Class Malacostraca
Order Isopoda
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Dorso-ventrally compressed
Cephalon: head plus first thoracic segment
Non-stalked eyes; compound
Antennae 2 long
Pereon = rest of thorax


Seven pairs of similar legs
Abdomen: pleopods for swimming, respiration
Class Maxillopoda
Infraclass Cirripedia: barnacles

Carapace covered by calcareous plates
 Four valves

Head
 No antennae after settling
 3 pairs of mouthparts

Thorax
 Six pairs of biramous appendages (cirri)
 Long penis


No abdomen
Feeding
Order Cirripedia: the barnacles
Balanus,
Semibalanus sp.
Chthamalus sp.
Pollicipes
polymerus
Cirripedia: life cycle
http://www.jst.go.jp/erato/project/fck_P/icons/grf1_1.jpg
Class Maxillopoda
Subclass Copepoda
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Abundant
Key primary consumer
Appendages
 Antennae


Long first antennae: propulsion
Second antennae: feeding
current
 Thoracic appendages


T1 is a maxilliped
T2-T5 : periopods (swimming)
 No abdominal appendages
 Oil droplets: lipid reserves
and buoyancy