BIO 385 — Invertebrate Zoology
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Invertebrate Diversity
Phylum Arthropoda
Subphylum Crustacea

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Subphylum Crustacea

Characteristics

  • 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

Class 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
Nauplius
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
Daphnia
Water Flea, Daphnia magna
See also labeled photo.
Moina
Water Flea, Moina sp., ventral view
Bosmina Water Flea
Water Flea, Bosmina sp.

"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 (clam shrimp) is paraphyletic and part of larger clade Diplostraca, which also includes the Cladocera; 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)
Vernal Clam shrimp
Vernal Clam Shrimp, Eulimnadia sp., ventral view (Order Spinicaudata; native to AZ)

Class 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
California Mantis Shrimp
California Mantis Shrimp, Hemisquilla californiensis
Stomatopod
Stomatopod, Gonodactylus scyllarus
Peacock Mantis Shrimp
Peacock Mantis Shrimp, Odontodactylus sp.
Mantis Shrimp
California Mantis Shrimp, Hemisquilla californiensis
Mantis Shrimp
Caribbean Rock Mantis Shrimp, Neogonodactylus bredini
Mantis Shrimp specimen
Mantis Shrimp, dried specimen (family Squillidae); note that some legs are missing

Order Decapoda

  • Shrimp, crabs, lobsters, crayfish
  • One pair of anterior clawed appendages
  • Carapace well developed
  • Marine, freshwater, and terrestrial (few)
  • Main suborders are:
    • Astacidea: Crayfish & lobsters
    • Anomura: hermit, king & sand crabs
    • Brachyura: true crabs
    • Caridea: shrimp
Suborder Astacidea:
Crayfish
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.

Suborder Anomura:
Hermit Crab
Orange-clawed Hermit Crab, Calcinus tibicen
Sand Crab
Pacific Sand Crab, Emerita analoga
Pelagic Red Crab
Pelagic Red Crab, Pleuroncodes planipes.

Suborder Brachyura (true crabs):
Ghost Crab
Atlantic Ghost Crab, Ocypode quadrata; TX
Fiddler Crab
Fiddler Crab, Uca sp.; Belize
Shore Crab
Purple Shore Crab, Pachygrapsus crassipes
Arrow Crab
Arrow Crab, Stenorhynchus seticornis
Spider Crab
Giant Spider Crab, Macrocheira kaempferi.
Sharpnosed Crab
Sharp-nosed Crab, Scyra acutifrons; the encrusting algae, sponges, and anemones function as camouflage

Suborder Caridea (shrimp):
Spot Prawns
Spot Prawn, Pandalus platyceros
Fan Shrimp
Common Fan Shrimp, Atyopsis moluccensis, a fresh-water suspension feeder.
sexy shrimp
Sexy Shrimp, Thor amboinensis
Ghost Shrimp
Bay Ghost Shrimp, Neotrypaea californiensis; CA
Fire Shrimp
Red Fire Shrimp, Lysmata debelius, a type of cleaner shrimp.
Atlantic White Shrimp
Atlantic White Shrimp, Penaeus setiferus, is a commercially fished species

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
Sow Bugs
Woodlouse, Trachelipus rathkii, ventral view; AZ
Aquatic Isopod
Fresh Water Isopod, Asellus sp.
Pillbugs
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
Rocky Shore Isopod
Rocky Shore Isopod, Ligia occidentalis; CA
Scavenging Isopod
Scavenging Isopod, Cirolana harfodi; CA
Paddletailed Isopod
Large Paddle-tailed Isopod, Idotea stenops; CA
Sea Pills
Sea Pills, Exosphaeroma inornata, an intertidal species; CA
Tongue Louse
Tongue-eating Louse, Cymothoa exigua, an oral parasite of fishes; preserved specimen

Order Amphipoda

  • Scuds
  • Carapace absent
  • Laterally compressed
  • Humpbacked appearance
  • Marine and fresh water (some semiterrestrial)
FW Scud
Freshwater Scud
Amphipod
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

Class Copepoda — Copepods

Characteristics

  • 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
Copepod
Fresh-water copepod, Cyclops sp.
Fish louse
Fish Louse, Caligus sp., an external parasite of fishes that feeds on mucus and skin (preserved specimen)
Copepod Larva
Nauplius Larva of Copepod
Cyclopoid Copepod
Marine harpacticoid? copepod, female with eggs, in lateral view
Trigiopus Copepod
Marine harpacticoid copepod, Trigiopus sp.

Class Ostracoda — Seed Shrimp

Characteristics

  • 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)
  • Very diverse, with over 30,000 species
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

Class Pentastomida — Tongue worms

Characteristics

  • Internal parasites of vertebrate respiratory tracks
  • Anatomically simplified, generally worm-like
  • Limbs reduced to 4 claw-bearing nubs in adults
  • Simple digestive system; lack circulatory, excretory, respiratory organs
Tongue Worm
Preserved Tongue worm, possibly Kiricephalus sp., collected from a water snake (Nerodia sp.)
Tongue Worm
Head of preserved Tongue worm, possibly Kiricephalus sp., collected from a water snake (Nerodia sp.)

Class Cirripedia — Barnacles

Characteristics

  • 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 13 May 2023 by Udo M. Savalli ()
Images and text © Udo M. Savalli. All rights reserved.