Polychaeta

Overview

Polychaeta is the largest class within Phylum Annelida. This class is primarily composed of Marine worms.

Characteristics

• Metameric Body Segmentation
  • The body is arranged in metameres, small body segments.
  • Allows compartmentalization in case of injury.
  • Allows specialization for certain bodily functions.
• Parapodium
  • Extensions of the body that allow for locomotion.
  • Have Setae sticking out of the ends, bristles which aid in locomotion.
• Prostomium
  • “Mouth” of the annelid.
  • Contains eyes, palps, antennae.
• Cuticle
• Move by “Undulating”
  • Longitudinal muscles that run the length of the worm contract and relax.
  • Allow the animal to change the frequency and amplitude of their waving.
• Digestive system fitting their food source.
  • Some predatory members have jaws with poison glands for subduing their prey
  • Others are herbivorous or filter feeders.
• Closed circulatory system
  • Dorsal and Ventral Aorta
  • Parapodia increase surface area for gas exchange.
• Nervous System
  • Suprapharyngeal ganglion
  • Sensory Fuctions
  • Motor Functions
  • Subpharyngeal ganglion
  • Regulate contraction of muscles
• Excretion Systems
  • Protonephridia
    
  • Similar to the structure found in Platyhelminthes
  • Bulbs attached to tubes drive wastes out of the body
  • Metanephridia
  • Open tubes drive wastes to the outside
• Reproduction
  
  • Mostly Sexual, Dioecious
  • Can reproduce by Budding

Sources:

Campbell & Reece. "Biology" Benjamin Cummings. 6th Edition, 661
Miller & Harley. "Zoology" McGraw Hill. 7th Edition, 212-217

Pol`y*chae"ta (?), n. pl. [NL., from Gr. many + hair.] Zool.

One of the two principal groups of Chaetopoda. It includes those that have prominent parapodia and fascicles of setae. See Illust. under Parapodia.

© Webster 1913.