BIOL 112 Lecture 30

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Arthropoda

Hexapoda

Lifestyles

• Pollinators
• Pests
• Disease Vectors

Hox genes first discovered in Drosophila melanogaster

Crustacea

• barnacles, lobsters, crabs; mostly aquatic
• pill bugs, wood lice; a few terrestrial

cuticle strengthened with CaCO₃

Lophotrochozoa

Diverse group (18 phyla), but grouped based on DNA sequence similarity and some shared morphology

• Platyhelminthes
• Annelida
• Lophophorates
• Rotifera
• Mollusca

defining characteristics:

• Trochophore larvae
• Lophophore: ciliated filter-feeding structure

Mollusca

Classes:

• Gastropoda
• Polyplacophora
• Bivalvia
• Cephalopoda

Common features:

• shell / valve
• mantle (secretes valve)
• visceral mass (contains gut)
• Radula (used for scraping food)
• Large muscular foot

some structures may me modified or reduced/absent in some molluscs

• radula is absent from cephalopods (replaced by beak) and bivalves (suspension feeders)
• shell is absent from slugs, highly reduced in cephalopods
• foot is modified in cepalopods into a siphon system

Cephalopoda

Active predators

• well-developed sensory systems (eyes)
• #closed circulatory system
• Beak for biting
• Jet siphon for locomotion
• camouflage

Closed Circulatory System

Separate blood and interstitial fluid

c.f. open circulatory system, where blood and interstitial fluid is mixed

Veins and arteries carry enclosed blood to and from the heart (respectively)

More "costly" to build and maintain than an open circulatory system, but more efficient (esp. in large, active animals)