Phylum Annelida• Worldwide distribution.

• Habitat: Saltwater, Freshwater, and Land.

• Marine. Found in benthic regions and on the surface.

Annelid “little rings”

Latin singular: AnnulusPlural: Annuli Annelid

• Metamerization- Division of the body into a series of repeating segments.

• What other organisms, besides those in this phylum, are metameric?

• What is the evolutionary advantage to metamerization?

Phylum Annelida (3 classes)• Oligochaeta- Earthworms

• Hirudinia- Leeches

• Polychaeta- Freshwater/Marine worms

Anatomy• All Annelids (except leeches) have setae.• Setae- Short hairs/bristles.• Function: Anchor during movement. Short setae: land Long setae: aquatic

• Body segments separated by septum Septum: Internal wall

• Closed circulatory system• Well-developed nervous system (brain + nerve cords)

MovementHydrostatic Skeleton: A skeleton made

up of fluid under pressure in closed compartments.

Circular Muscle

Longitudinal Muscle

Longitudinal MuscleCircularMuscle

Movement

• Contraction of longitudinal muscles- shorten

• Contraction of circular muscles- lengthen

• Alternate muscular contractions: longitudinal, circular, longitudinal, circular, etc.

How are they used?

Worm Ranch: http://dsc.discovery.com/tv-shows/dirty-jobs/videos/worm-rancher.htm

Eating a worm: http://dsc.discovery.com/tv-shows/man-vs-wild/videos/whopper-worm.htm

Reproduction

• Sexual & Asexual• Polychaets- Dioecious•Oligochaetes & Hirudinia- Monecious

• Clitellum: leeches and earthwormsClass Polychaets do not use clitellum for reproduction!

Class Oligochaeta (Earthworms)

•Oligochaetes & Hirudinia- Monecious

•Clitellum: leeches and earthwormsClass Polychaets do not use clitellum for reproduction!

Class Hirudinida (Leeches)

• Habitat: Primarily freshwater, few marine. Abundant in tropical regions.

• Size: Most between 2-6 cm in length.

• Color: Variety of colors and patterns: black, brown, red, or olive green.

Reproduction Monecious. After fertilization, clitellum secretes a

mucous –like cocoon that receives eggs & sperm.

Bury mucous cocoon in mud. Development process is similar to

Oligochaetes.

How are leeches beneficial? Medicinal uses: circulation, anti-

clotting(Produces anticoagulant that prevents blood from clotting.)

External parasite with suckers on each end.

Class Polychaeta (Freshwater/Marine worms)Habitat: mucous-lined burrows near

low tide. Most active at night.

Size: Grows up to 30-40 cm in length.

Diet: Particle feeders. Use cilia or mucus to obtain food. Consume plankton.

AnatomyParapoda: Appendages of

Polychaetes. Function: Locomotion & breathing.

Fire-worm

Featherduster-worm

Scale-Worm

Coelomate vs. AcoelomateWhich are Annelids?