BIOEE 1780 Lecture Notes - Lecture 15: Aposematism, Cestoda, Cephalization
7 May 2018
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Protostomes
• Synapomorphies:
o Anterior brain
o Ventral nervous system consisting of paired or fused longitudinal nerve cords
• Two Major Clades:
o Lophotrochozoans
o Ecdysozoans
Lophotrochozoans
• Synapomorphy: DNA
• A collar of feeding tentacles known as a lophophore around the mouth, which are involved in
feeding and gas exchange
• Free living larva known as a trochophore
o Move via a beating band of cilia around its middle
o Also used to bring food particles to its mouth
o Has been lost in some groups
• Still present in annelids and mollusks
• Part of bilateria
o Bilaterally symmetric
o Triploblastic
• Have increased cephalization of the anterior brain
• Examples: flatworms, annelids, mollusks
Advantages of Bilaterality and Cephalization
1. Locomotion
2. Predation
3. Regeneration
Cephalized portion of the body (head) encounters the environment first.
• Sensory organs
• Feeding systems
Bilaterality improves locomotion - allows wormlike/snakelike movement.
Flatworms: most are internal parasites (particularly of vertebrates)
• Synapomorphy: DNA
• Lophotrochozoans
• Acoelomate
• Use the same opening as the mouth and anus (no flow-through gut) → blind gut
• Reduced or no digestive tracts
o Absorb digested food from the guts of their hosts
• No circulatory system
o Each cell must be near a body surface
o Results in flattened body form
• When cut in half, they can regenerate.
o The half that has the head has a greater chance of regenerating.
o Occurs by fission
• In free-living taxa, there is cephalization with ventral nerves.
• Examples
Document Summary
Synapomorphies: anterior brain, ventral nervous system consisting of paired or fused longitudinal nerve cords. Lophotrochozoans: a collar of feeding tentacles known as a lophophore around the mouth, which are involved in. Free living larva known as a trochophore: move via a beating band of cilia around its middle, also used to bring food particles to its mouth, has been lost in some groups. Still present in annelids and mollusks: part of bilateria, bilaterally symmetric, triploblastic, have increased cephalization of the anterior brain, examples: flatworms, annelids, mollusks. Advantages of bilaterality and cephalization: locomotion, predation, regeneration. Cephalized portion of the body (head) encounters the environment first. Flatworms: most are internal parasites (particularly of vertebrates: acoelomate. In free-living taxa, there is cephalization with ventral nerves: examples, flatworms: free-living marine carnivores and detritivores, aposematic coloration, tapeworms: parasitic. Infect many species: need at least 2 hosts for life-cycle, flukes: parasitic.
