BIO 385 Invertebrate Zoology
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Invertebrate Diversity
Phylum Arthropoda
Subphylum/Class Crustacea

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Class Crustacea


  • Head (cephalon) with 5 pairs of appendages; including 2 pairs of antennae
  • Trunk usually divided into thorax and abdomen
  • Appendages mostly biramous
  • Have compound eyes (often on stalks) and ocelli
  • Predominantly marine; some fresh water or terrestrial
  • Unique nauplius larva
  • Taxonomic note: Crustacea is likely paraphyletic

Subclass Branchiopoda

Order Anostraca

  • Fairy & brine shrimp
  • Numerous (up to 19) swimming appendages
  • Lack a carapace
  • Many in hypersaline environments or vernal pools
Brine Shrimp
Brine Shrimp (aka Sea Monkeys), Artemia franciscana
Brine Shrimp, Artemia sp., Nauplius larva
RT Fairy Shrimp
Red-tailed Fairy Shrimp, Streptocephalus sp., female

Order Notostraca

  • Tadpole Shrimp
  • Shield-like carapace covers thorax
  • Ring-like segments on narrow abdomen
  • 2 long caudal rami
  • Live in temporary pools; eggs withstand dessication
Tadpole Shrimp
Longtailed Tadpole Shrimp, Triops longicaudatus
Tadpole Shrimp Ventral
Longtailed Tadpole Shrimp, Triops longicaudatus, ventral view

Order Cladocera

  • Water Fleas
  • Large folded carapace is not hinged
  • Body segmentation reduced
  • Use enlarged antennae for locomotion
  • Large central compound eye
Water Flea, Daphnia magna
See also labeled photo.
Water Flea, Daphnia lumholtzi
Bosmina Water Flea
Water Flea, Bosmina sp.

Order "Conchostraca"

  • Clam shrimp
  • Two part carapace is hinged dorsally
  • Carapace usually has growth lines, looks much like a small clam
  • Carapace is usually transparent: eyes and legs visible
  • Use enlarged antennae for locomotion
  • Lives in vernal (temporary) pools and ponds
  • Conchostraca is paraphyletic; clam shrimp now split into 3 orders
Clam shrimp
Clam shrimp (collected at Tres Rios, Tolleson, AZ)
Vernal Clam shrimp
Vernal Clam Shrimp, Eulimnadia sp., hermaphrodite with eggs (Order Spinicaudata; native to AZ)

Subclass Malacostraca

Order Stomatopoda

  • Mantis shrimp
  • 2nd pair of appendages form large raptorial leg with stabbing or club tip
  • Large compound eyes on stalk
  • Usually brightly colored
Mantis Shrimp
California Mantis Shrimp, Hemisquilla californiensis
Mantis Shrimp
Caribbean Rock Mantis Shrimp, Neogonodactylus bredini
Stomatopod, Gonodactylus scyllarus

Order Decapoda

  • Shrimp, crabs, lobsters, crayfish
  • One pair of anterior clawed appendages
  • Carapace well developed
  • Marine, freshwater, and terrestrial (few)
Burrowing Crayfish, Cambarus dubius; KY
See also labeled photo.
Crayfish ventral view
Northern Crayfish, Orconectes virilis, ventral view of male
See also labeled photo.
Crayfish Anatomy
Northern Crayfish, Orconectes virilis, dissected female & male
See also labeled photo.
Spiny Lobster
California Spiny Lobster, Panulirus interruptus
Hermit Crab
Hermit Crab, Pagurus sp.; Belize
Sand Crab
Pacific Sand Crab, Emerita analoga; CA
Ghost Crab
Atlantic Ghost Crab, Ocypode quadrata; TX
Fiddler Crab
Fiddler Crab, Uca sp.; Belize
Arrow Crab
Arrow Crab, Stenorhynchus seticornis
Spot Prawns
Spot Prawn, Pandalus platyceros.
Fan Shrimp
Common Fan Shrimp, Atyopsis moluccensis.
Sharpnosed Crab
Sharp-nosed Crab, Scyra acutifrons; the encrusting algae, sponges, and anemones function as camouflage

Order Isopoda

  • Sowbugs, pillbugs, etc.
  • Carapace absent
  • Dorso-ventrally flattened
  • Many can roll into ball
  • Marine and terrestrial environments
Sow Bugs
Sowbugs, Porcellio scaber; CA
Rocky Shore Isopod
Rocky Shore Isopod, Ligia occidentalis; CA
Paddletailed Isopod
Large Paddle-tailed Isopod, Idotea stenops; CA
Pillbugs, Armadillium vulgare; AZ (only some isopods can roll into a ball)
Giant Isopod
Giant Deep Sea Isopod, Bathynomus giganteus; ≈30cm long
Sand Isopod
Intertidal Sand Isopod, Gnorimosphaeroma sp.?; CA

Order Amphipoda

  • Scuds
  • Carapace absent
  • Laterally compressed
  • Humpbacked appearance
  • Marine and fresh water (some semiterrestrial)
FW Scud
Freshwater Scud
Amphipod; LaJolla, CA
Skeleton Shrimp
Skeleton Shrimp, Caprella sp.

(Order Mysida)

  • Opossum shrimp
  • Similar to true shrimp (Decapoda) but...
  • Lack free-swimming larvae
  • Embryos carried in brood pouch between legs
  • Marine and fresh water
  • Not likely to be represented in lab
Mysid shrimp
Opossum shrimp

Subclass Copepoda Copepods


  • Lack carapace, but have cephalic shield
  • Small (<2 mm)
  • Single median eye
  • 6 thoracic and 5 abdominal segments
  • No abdominal appendages or gills
  • Mostly marine, planktonic drifters
Fresh-water copepod, Cyclops sp.
Fish louse
Fish Louse, Caligus sp. (preserved specimen)
Copepod Larva
Nauplius Larva of Copepod

Subclass Ostracoda Seed Shrimp


  • Almost completely enclosed within hinged, bivalved carapace
  • Overall seed or bean-shaped appearance (ventral edge often somewhat concave)
  • Carapace is often pigmented
  • No more than 2 pairs of post-cephalic appendages
  • Most are tiny (<2 mm)
Seed Shrimp
Seed Shrimp, Cypris sp.
Seed Shrimp
Seed Shrimp, probably Potamocypris sp.
Seed Shrimp
Fossil Ostracods, Eoleperditia sp.; Ordovician Period, 452-445 mya; KY

Subclass Cirripedia Barnacles


  • Sessile; attach to various surfaces as adults
  • Attach with ventral surface up
  • Most secrete thick calcium carbonate shell
  • Head reduced; abdomen absent
  • Thoracic legs modified for suspension feeding (cirri)
  • Some species are parasitic
N Rock Barnacles
Northern Rock Barnacles, Balanus balanoides, feeding; ME
Giant Acorn Barnacle
Giant Acorn Barnacle, Balanus nubilus, feeding
Acorn Barnacles
Small Acorn Barnacles, Chthalamus fissus and 2 White Acorn Barnacles, Balanus glandula; CA
Volcano Barnacles
Volcano Barnacles, Tetraclita rubescens; San Diego, CA
Leaf Barnacles
Leaf (or Goose-necked) Barnacles, Pollicipes polymerus; CA
Pelagic Goose Barnacles
Pelagic Goose Barnacles, Lepas anatifera attach to driftwood and seaweed; CA
This page last updated 12 March 2017 by Udo M. Savalli ()
Images and text Udo M. Savalli. All rights reserved.