This document summarizes key characteristics of the phylum Annelida. It describes the three classes - Polychaeta, Aelosomata, and Clitellata (with subclasses). It then discusses the basic body plan, skeletal system, circulatory system, digestive/excretory system, reproductive system, nervous system, and some examples of specific annelid worms like the sea mouse, giant feather duster, leeches, giant Australian earthworm, colonial polyps, and king ragworm.

1. Phylum Annelida
Kaitlyn Anticoli and Madeline Avallon

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