Annelida Part IIDomain: Eukarya

Kingdom: Animalia

Phylum: Annelida

Class: Oligochaeta

Class: Polychaeta

Class: Hirudinea

Essential Questions

1. Describe the 3 types of body plans for polychaeta based on how they hunt.

2. Describe the larval type for the polychaeta.

3. Describe the differences in setae and parapodia in each of the three classes of Annelids

Class Polychaeta

• About 2/3 of all Annelids

• Name = “many bristles”

• Numerous setae that

project from parapodia

• Most all are marine

– some are free-swimming

predators that use jaws to

feed on small animals

– others feed on sediment or

use tentacles to scour for

food

– See oligochaeta for other

characteristics

Structure (body plan)• Body form reflects niche

(job) and habitat– All have antennae and

specialized mouthparts

– Active hunters• jaws

• setae and parapodia modified for swimming

• Super inefficient

– Burrowing deposit feeders• antennae modified into

tentacles that search for food

– Suspension-feeders• live inside tubes that they

secrete that filter food from the water

Reproduction• Simple reproductive structures

• Various per species

– Some release eggs and sperm from individual males and females

• Trocophore larvae - Indirect

development

– Only Annelid class that has a larval stage!!!!!

Example organisms

• A: Nereis - predator

• B: Feather Duster worm – filter

feeder

• C: Spirorbidae – filter feeder

Other examples• Filter feeders

• Chaetopterus –Parchment Tube Worm

• Innkeeper worm

• Terebellid

– Spaghetti worm

• Glycera

Class Hirudinea• Smallest class

• 300 species of LEECHES!!!!

• Most live in calm freshwater

• No setae or parapodia

• Sucker on anterior and posterior ends– Surround mouth and anus

• Pharynx just behind mouth

– Can crawl or swim using circular & longitudinal muscles and suckers

• Clitellum present – reproduction similar to Oligochaeta

Feeding and Digestion• hunt or scavenge

– suck prey whole using pharynx– Or pierce prey body and suck

out fluids and soft tissues• Once attached to host they

secrete anesthetic and anti-clotting substances

• Can eat 10 times its weight in blood.

• Medical importance

• Digestion system is similar to Oligochaeta