Arthropoda: Crustaceans (Crabs and Lobsters)

Crustaceans

• Crabs, Lobsters etc.
• 40,000 - 50,000 living species
• Mostly marine, some freshwater and terrestrial
• Large size range

Morphology

• 2 pairs of antennae
• Compound eyes on stalks
• Multiple lenses in each eye
• Cephalothorax
• Carapace: shielded cover that protects dorsal and lateral sides of body
• sometimes protects abdomen too
• Mandibles: primary mouthparts
• Single segment for biting and chewing
• 2 or more appendages help guide food to mouth
• Limbs
• Thoracic limbs: for locomotion
• Abdominal limbs: diverse use
• Swimming Photo by J C D | CC BY
• Filter feeding
• Holding eggs
• Exoskeleton
• Hardened with calcium carbonate
• Gills
• For gas exchange
• Wide and flat, fluffy
• Highly vascularized
• Thin unsclerotized cuticle
• Some terrestrial crustaceans use trachaea Example: Pillbugs

Crustacean Life Cycle

• Highly variable
• Direct and Indirect development
• Separate sexes
• Except for barnacles (hermaphroditic)
• Copluate to transfer sperm
• Females brood eggs until they hatch

Ecology and Importance

• Important detritivores, scavengers and predators
• Some scavenge dead plant and animal matter
• Some predatory
• Some are commensalists or parasites of verts
• Planktonic crustaceans feed large number of verts Examples: Whales and fish
• Some filter feed
• Motile Examples: fairy shrimp
• Sessile Examples: barnacles