2. Phylum Classes
1. Polychaeta Class
2. Aelosomata Class
3. Clitellata Class (superclass)
a. Oligochaeta Subclass
b. Branchiobdella Subclass
c. Hirundinea Subclass
3. Basic Characteristics
● annelid means "little
rings"
● distinguished by
segmentation and
body cavity
● range in length from
1 mm- 3 m
● bilaterally
symmetrical
4. Basic Characteristics
● digestive tract
● ability to survive in
most environments
● possesses 3
separate sections:
prosomium
(mouth), trunk and
pygidium (tail)
● cephalopods
5. Skeletal System
● coelum: fluid-filled cavity that separates gut
from body wall
● hydrostatic skeleton
○ coelum which creates hydrostatic
pressure and acts as a hydrostatic
skeleton
○ most primitive skeletal system
6. Circulatory System
● true closed circulatory system
● two main vessels are
○ dorsal blood vessel: blood moves
anteriorly
○ ventral blood vessel: blood moves
posteriorly
● aortic arches: "hearts"
○ dark, expanded structures on either side
of the esophagus
○ only function in pumping blood from the
dorsal to the ventral vessels
7. Digestive and Excretion
System
● annelids break down organic material to
create rich soil
● have a mouth that connects directly to the
anus without an intermediate stomach
○ allows annelids to continuously eat and
excrete waste as they burrow down
through the soil
8. Reproductive System
● normally sexual
● gonochoristic or hermaphroditic
● asexual reproduction: part of their tail is
released which grows into a new organism
(fission)
● sexual reproduction: fluids are transferred
from the male pore to the female ovipore.
9. Nervous System
● primitive brain (ganglionic mass) connected
by a ring of nerves to a ventral nerve cord
that runs the length of the body
● sense organs include eyes, taste buds,
tactile tentacles, and organs of equilibrium
called statocysts.
10. Evolved Characteristics
● humans, like annelids, have a brain and
nerve cord (spinal cord)
● frogs have a coelum
○ annelid coelum contains fluid that creates
pressure and acts as hydrostatic skeleton
○ frog's coelum contains organs such as the
lungs and is where lymph cirulates
● anthropods like insects are also segmented
11. Sea Mouse
● short, broad, segmented body,
● found in moderately deep water
● dorsal surface has 15 pairs of raised scales
○ the space between the scales and the
body surface forms a channel for the flow
of water carrying oxygen
● 6 to 8 in. long and 2 in. wide
12. Giant Feather Duster
● marine segmented worms
● attached to rocks or sand
● from 1/2 to 10 inches long
● Encased in a translucent tan tube made of
protein and filtered particles
● about 30 feather-like gills (radioles ) on each side of
their tube for respiration and feeding
● covered in eyespots to know when danger is near to
retreat into their tube
● live in groups in tide pools or near the low-tide line
● feed on small particles and plankton floating in the water
13. Leeches
● cylindrical or slightly flattened body with
suckers at either end for attaching to prey.
● salivary secretions substances that promote
blood flow like hirudin
● can be small enough to enter human body or
as big as adult human forearm
● do not feed vey often
14. Giant Australian
Earthworm
● largest is 13 feet long!
● need water so rarely leave moist
underground
● lay eggs that take year to develop
● endangered because can't handle human
interaction/pesticides etc.
● annual worm festival with Earthworm Queen
15. Colonial Polyps
● one-way digestive tract
● prefer mild flow environments but benefit
from occasional stronger water flow
● round with a mouth in the middle and a ring
of tentacles around the mouth
● tentacles possess cells that sting, paralyze,
and catch prey
16. King Ragworm
● prefer estuarine environment with mud
● can grow to 24 inches
● sharp teeth that grab and hold onto prey
● locomotory feet
○ aid swimming
○ circulate water
○ bring food to worm
● predator