Annelida Lab

Nereis (Neanthes) Parapodia












Lumbricus Cross Sections

behind clitellum-



















Live Feather Duster













Live Paddleworm










Live Ragworm












Live Orange Fire Worm









Live Earthworm Dissection

All Pictures Above Were Taken By Douglas Ericson (Me).


Phylum Annelida: The segmented worms or ringed worms.

Class Polychaeta: Known as the bristle worms, they have well defined segmentation with parapodia on each segment. Generally marine organisms.

Class Clitella: A class of annelids that have a collar like structure known as the clitellum.

Subclass Oligochaeta: Worms that have few setae and lack parapodia. Earthworms are from this subclass.

Subclass Hirudinea: This subclass includes the leeches.

Metamerism: Segmentation. The body is divided into repeating segments.

Septa: A wall of tissue that divides a structure or cavity into smaller ones.

Hydrostatic skeleton: A fluid filled membrane structure which acts as something for muscles to act on.

Closed circulatory system: A circulatory system where the circulatory fluid is held in vessels.

Dorsal Vessel: One of the three main vessels that supply circulatory fluid to the tissues of annelids. Located on the dorsal side of the worm.

Ventral Vessel: One of the three main vessels that supply circulatory fluid to the tissues of annelids. Located on the ventral side of the worm.

Lateral vessel: One of the three main vessels that supply circulatory fluid to the tissues of annelids. Located on the lateral side of the worm.

metanephridia: Excretory tubules that open into the body cavity.

nephrostome: The opening that connects the nephridium to the coelom.

nephridiopore: The opening of the nephridium that leads to the external environment.

prostomium: The most anterior segment of the annelid. It holds the mouth.

peristomium: The segement just behind the prostomium

tentacles: A noodle-like appendage that has a variety of uses based off the attached organs. Could hold sensory organs, could also be used to draw food to the mouth.

palps: A pair of appendages found near the mouth of an annelid worm. They vary in size and can be segmented as well.

mouth: An opening that allows material into the digestive system.

proboscis: A tube like mouth piece that is used for eating, or for attachment via sucking.

jaws: A structure found in predatory polychaetes that is used to seize prey or bite into prey. They can also be used to carry items.

parapodia: An appendage that extends from a section of the annelid worm.

acicula: A chitinous hair-like structure in a parapodia that supports the structure of the parapodia.

setae (chaetae): Stiff, hairlike structures that are used for locomotion in annelid worms.

errant: An organism that is free to move around.

sedentary: An organism that stays in one place generally. Does not want to move.

tube dwellers: A type of annelid worm that is sedentary and lives inside tubes that are self made in some cases and other times are not.

suspension feeding: A feeding mechanism that involves taking in material that is suspended in the water column.

deposit feeding: A feeding mechanism that involves finding and eating food material that has fallen to the sea floor, the benthos.

atoke: The anterior segment of a polychaete worm that grows the epitoke.

epitoke (epitoky, epitokous): The most anterior section of a polychaete worm that is able to sexually reproduce. The sexual part of the worm.

clitellum: A circular tissue that surrounds a segment of clitellate worms that contains reproductive organs.

testes: Male reproductive organs, produce sperrm.

ovary: Female reproductive organs, produce eggs.

seminal receptacle (spermatheca): A structure that receives sperm during sexual exchange in annelid worms.

seminal vesicle: An organ that produces and releases sperm in annelid worms.

annelid digestive system: Consists of a mouth that is connected to the gut which runs through the center of the body. The gut leads to the anus located on the posterior end of the worm, the pygidium. The gut is separated from the body wall by a coelom.

mouth: Anterior opening that brings material into the body, to the gut.

pharynx: The part of the gut that follows the mouth. It uses muscles to push food down to the esophagus.

esophagus: This part of the gut brings food from the pharynx to the crop.

crop: This part of the gut stores the food until the gizzard is ready to take it in.

gizzard: Contains rocks or other hard material, that the worm has eaten. These hard objects are used to grind up the food that is brought in.

intestine: Where the ground food is digested by enzymes and absorbed into the circulatory system via blood vessels.

typhlosole: A fold in the intestine wall which increases surface area.

cerebral ganglia: A concentration of nerve cells on the anterior end of the worm where the nerve cord starts.

subpharyngeal ganglia: The largest concentration of nerve cells found on the posterior end of the worm.

nerve ring: A pair of ganglia on the anterior end of the worm that creates a ring of nerve cells around the pharynx.

ventral nerve cord: The nerve cells that connect the anterior ganglia to the posterior ganglia.

leeches- anterior, posterior suckers: Structures that allow the leech to attach itself to a food source, organism. These may contain hooks or barbs to release blood from the organism it is attached to.