Phylum- Annelida



Group: Annelida


Lumbricus (Earthworm) Dissection






Nereis/ Class: Polychaeta



Lumbricus/ Class: Clitellata


Leeches/ Class: Clitellata



Casts of Annelid burrows


Earth Worm Mouth/ Image Magnification 10x


Reef ID of Species of Marine Polychaetes

Common Name: Christmas Tree Worm/Sedentary

Habitat: Burrow into coral reefs of tropical waters

Special Features: Plumes/tenticles used for passive feeding on suspended food particles and plankton in the water

Common Name: Bearded Fireworm/Sedentary

Habitat: Reefs beneath stones in rocky or sea-grass areas, found in the western Atlantic

Special Features: Groups of white bristles on each side that are venom filled chaeta and are penetrated into flesh of prey

Common Name: Split Crown Feather Duster/Sedentary

Habitat: Lives in solitary or small groups. In tubes of sand all over the Caribbean

Special Features: Gills filter food, lives in tubes of sand for protection


Metamerism– A linear series of body segments fundamentally similar in structure

Septa– Separate the segments of many species

Hydrostatic skeleton–  Consists of a fluid-filled cavity, the coelom, surrounded by muscles. The pressure of the fluid and action of the surrounding muscles are used to change an organism’s shape and produce movement, such as burrowing or swimming

Closed circulatory system– The blood closed at all times within vessels of different size and wall thickness. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities.

Dorsal vessels– A central pulsating blood vessel along the back, acting as a heart.

Ventral vessels– Carries blood to the back portion of the worm’s body, the only one part of the worm’s closed circulatory system

Lateral vessels– Blood-pumping organ of an earthworm

Metanephridia– Nephridia which open into the coelom, the open end nephrostome being ciliated

Nephrostome–  The ciliated funnel by which some types of nephridia open into the coelom

Nephridiopore– The excretory orifice of a nephridiu

Prostomium– The first body segment in an annelid worm’s body in the anterior end

Peristomium– The second body segment in an annelid worm’s body in the anterior end

Tentacles– Act as gills, can be venom filled

Palps– an appendage found near the mouth, used for predating 

Mouth– Entrance to the digestive tract

Proboscis– tubular part of the mouth used for feeding and sucking

Jaws- Food acquisition, conveyance to the mouth, and/or initial processing (mastication or chewing

Parapodia– Un-jointed lateral outgrowths that bear the chaetae

Acicula– Chitinous support rods within parapodia

Setae (chaetae)– Stiff bristles present on the body, attach to the surface and prevent backsliding during peristaltic motion

Sedentary– Do not move very much

Errant- Mobile

Tube Dweller–  Live in a tough tube for protection, can stick its head out in order to capture its food, camouflages well and has many muscles, has many arms that open in order to capture food particles

Suspension Feeding– Feeds on material (such as planktonic organisms) suspended in water and that usually has various structural modifications for straining out its food

Deposit Feeding– Obtain food particles by sifting through soil

Atoke– The anterior sexless part of certain polychaete worms from which grows the sexual portion

Epitoke (epitoky, epitokous)The posterior portion of marine polychaetes; contains the gonads.

Clitellum– Thickened glandular and non-segmented section of the body wall near the head

Testes- Paired male reproductive gland that produces sperm and secretes testosterone

Ovary– An ovum-producing reproductive organ, found in double pairs in the female

Seminal receptacle (spermatheca)– Sexual selection in which sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract

Seminal vesicle– Secrete fluid that partly composes the semen.

Annelid digestive system:

Mouth- Entrance to the digestive tract

Pharynx– Cone-shaped passageway leading from the oral and nasal cavities in the head to the esophagus and larynx

Esophagus– A muscular tube connecting the throat (pharynx) with the stomach.

Crop– Storing food after it has passed through the esophagus, which possesses calciferous glands that release calcium carbonate

Gizzard– Uses stones that the earthworm eats to grind the food completly

Intestine– Digestion and absorption of food

Typhlosole– internal fold of the intestine or intestine inner wall

Cerebral ganglia– one of a pair of ganglia situated in the head or anterior part of the body in many invertebrates in front of or dorsal to the esophagus

Subpharyngeal ganglia– Bilobed ganglion located below the pharyngeal bulb in arthropods and annelids, which is the first of five ventral ganglia; it is connected to brain by two connectives surrounding pharyngeal apparatus.

Nerve ring– The ring of nerves surrounding the mouth

Ventral nerve cord– consists of cerebral ganglia anteriorly with the nerve cords running down the ventral plane of the organism

Leeches- anterior, posterior suckersThe anterior sucker is for feeding and the posterior sucker is for leverage


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