Coelomate Worms:
Annelids
Chapter 13
Phylum Annelida
• Important Groups
– Earthworms
– Tube worms
– Leeches
• Habitat
– Aquatic: Marine or Freshwater
– Terrestrial: soil
Phylum Annelida
• Food Source:
– Predators, Scavengers, Filter feeders, & Herbivores
• First substrate feeders
• Unique Characteristics:
– First group with closed circulatory system
– Segmented – each segment as a complete,
independent organism
Skeletal & Body System
• Hydrostatic skeleton for support and
movement
• Bilateral symmetry
• Segmented – “metamerization”
– Segments separated by septa
– Separate coelomic compartments
• Coelomates: True body cavity
• Have Setae – bristle-like structures projecting
from body (except leeches)
Muscular System & Movement
• Body wall made of circular & longitudinal
muscles
• Burrowing - movement
– Swallow sediments – do not push aside
– Each segment moves independently
Nervous Communication
• Independent ganglions in each segment
– Suprapharyngeal & subpharyngeal ganglia
• Nerve cords
– Double ventral
Cardiovascular System
• Complete, closed circulatory system
– Includes:
•
•
•
•
capillaries
arteries
veins
5 hearts
– Blood transports hormones, nutrients, & wastes
Respiratory System
• Respiratory pigments dissolved in blood
plasma carry oxygen
– Ex: hemoglobin – makes blood red
– Blood can be colorless, green, or red
• Oxygen diffuses across body wall
Digestive Food Capture
• Continuous gut extending from mouth to anus
with its own musculature
Excretory Waste Removal
• Excrete ammonia across body wall
• Nephridia
– Excretory organ
– Functions like kidneys
Reproductive System
• Sexual
– Monoecious or dioecious
– Possess gonads
• Asexual
– Budding
– Transverse fission
“Strobilation”