1. Lecture 17: Phylum Arthropoda, Part 2 Focus: Marine Crustacea
Invertebrate Zoology
Lecture 17: Phylum Arthropoda, Part 2
Subphylum Crustacea
Focus: Marine Crustacea

2. Lecture outline
Subphylum Crustacea
Overview
Selected groups

3. 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

4. Crustacea diversity: overview
Differences in tagmatization
Differences in appendage structure & function
Is the Class Remepedia truly “primitive?”

5. Class Malacostraca (Subclass Eumalacostraca)
Five-segmented head
Eight-segmented thorax
Six-segmented abdomen
“Tail” = telson + uropods
Carapace: partly/completely covers head & thorax

6. Class Malacostraca Thoracic appendages = thoracopods
Maxilloped
Cheliped
Pereopod
Abdominal appendages
Pleopod

7. Class Malacostraca
Order Euphausiacea: krill!

8. Class Malacostraca Order Euphausiacea: krill! Pelagic; schooling
Key food resource in marine food webs
Pereopods  feeding basket
Compression-filtration
Pleopods: swimming
Ancestral to Decapoda?

9. 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

10. Class Malacostraca Order Decapoda: Infraorder Caridea Shrimp
“Classic” Decapoda features
Most similar to early Decapoda?
Compare to Euphausiacea

11. Class Malacostraca Order Decapoda: Infraorder Caridea
Variety of local species
Oregon pink shrimp!
Protandrous hermaphrodites
Sustainable fishery (rare)
Cleaner shrimp
Bay shrimp

12. Class Malacostraca Order Decapoda: Infraorder Palinura Spiny lobsters
Similar to Caridea
Common in S. California
Lack powerful cheliped
Protection?
Group molting

14. Class Malacostraca Order Decapoda: Infraorder Anomura T4 chelate
Reduction of T8 & sometimes T7
Abdomen not key in movement
Pleopod reduction
Asymmetrical or tucked

15. Class Malacostraca Order Decapoda: Infraorder Anomura Hermit crabs
Role of reduced T7, T8
Asymmetry
Acquiring shells
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16. Class Malacostraca Order Decapoda: Infraorder Anomura Porcelain crabs
Role of reduced T8
Role of abdomen
Filter feeding
Other behaviors and oddities

17. Class Malacostraca Order Decapoda: Infraorder Anomura Mole crabs
Thoracopods specialized for “paddling” sand
Why doesn’t it suffocate when buried?

18. Class Malacostraca Order Decapoda: Infraorder Brachyura True crabs
T4-T8 well-developed; T4 chelate
Reduced abdomen
Adaptive value?

19. Shore crabs Hemigrapsus nudus Pachygrapsus crassipes
Hemigrapsus oregonensis

20. Cancer sp. crabs C. antennarius C. productus C. magister
C. oregonensis

21. Pugettia producta: shield-backed kelp crab

22. Reproduction: Cancer spp.

23. Reproduction

24. Class Malacostraca Subclass Eumalacostraca
Order Stomatopoda: mantis shrimps

25. 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

26. Class Malacostraca Order Amphipoda

27. Class Malacostraca Order Amphipoda
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

28. Caprellid with thoracic brood pouch

29. Class Malacostraca Order Isopoda
Idotea sp.
Ligiapallasii

30. Class Malacostraca Order Isopoda
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

31. 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

32. Order Cirripedia: the barnacles
Balanus, Semibalanus sp.
Pollicipes polymerus
Chthamalus sp.

33. Cirripedia: life cycle

34. Class Maxillopoda Subclass Copepoda
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