Phylum Annelida

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Zoology Lab Practical

Phylum Annelida

Segmented worms such as earthworms and leeches. Most are marine

Segmentation

Bodies are divided into segments called metameres (are externally linked by circular rings called annuli). Is the division of the bods into segments. Each segment contains similar components of all major organ systems.

Annelids

tiny chitinous have setae. Setae is used in locomotion, swimming, and burrowing (except for leeches)

Annelid Body plan

2 part head composed of a prostomium and a peristomium followed by a segmented body and a terminal portion called pygidium (bears the anus). Head and pygidium are not segments. Contains circulatory, respiratory, nervous, and excretory structures. Periotenba of adjacent segmens meet to form septa.

Annelid coelom

lined with peritnomeum that covers all the organs. filled with fluid and serves as a hydrostatic skeleton that helps the worm move

Cuticle

Thin outer layer surrounding the epdermis in annlieds

Not segmented

digestive system is in Annelids

Longitudinal dorsal and ventral blood vessels, ventral nerve cord

Follow the same path as the digestive system

Polychaeta, Oligochaete, Hirudinida

Classes of Annelida

Polychaeta

Marine Worms, 10,000 species

Polychaeta

have well differentiated head with specialized sense organs, paired appendages called parapodia on most segments, and no clitellum

Polychaeta

Contain setae arranged in bundles on the parapodia

Prostomium

Polychaeta part that bears eyes, tentacles, and sensory palps

Peristomium

Polychaeta part that surrounds the mouth and may bear setae, palps, or jaws

Trunk

Polychaeta part that is segmented and most segments bear parapodia

Parapodia

Used in crawling, swimming, or for anchoring the animal in its tube for Polychaeta.

Parapodia

Chief respiratory organs in Polychaeta

Clam, scale, fire, and tube worms

Representative Polychaetes

Clam Worms

Sometimes called sand worms, live in mucous-lined burrows in or near low tide, active at night, about 200 segments, parapodia is used for creeping and swimming. Feed on small animals, other worms, and a variety of larval forms

Scale Worms

most abundant and diverse of the polychaetes, flattened bodies are covered in broad scales, carnivorous and eat a wide variety of animals, many are commensals living in burrows of polychaetes or in association with cnidarians, molluscs, or echinoderms.

Fire Worms

have hollow brittle setea that contain a poisonous secretion. Feed on corals, gorgonians, and othe cnidarians

Tube Worms

tubes secreted can be parchmentlike, or leathery, some firm calcaerous, and some burrow into sand or mud. tubes attach to rocks on other surfaces. Most sedentary tube and burrow dwellers are particle feeders, using cilia or mucus to obtain food, typically plankton or detritus. Some are deposit feeders who protrude their heads above the mud extend long tentacles over the surface to find food

Oligochaeta

More than 3000 species, live in various habitats, include earthworms and many species that live in fresh water.

Oligochaeta

Class of Annelid that are terrestrial or freshwater, some are parasitic, and a few live in the marine water. Most have setae which can be long or short, straight or curved, blunt or needlelike, or arranged singly or in bundles.

Oligochaeta

Have a clitellum reproductive system (Annelids). Lack suckers

Earthworms

Called night crawlers, burrow in moist rich soil, live in tunnels. Most are scavengers, are hermaphroditic

Earthworms Digestion

Food enters the mouth and moves along the esophagus, then moves to the crop, gizzard which grinds the food into small pieces. Digestion occurs in the intestine. Absorption is increased by the typhlosole.

Chloragogen tissue

tissue that surrounds the intsetine and is the center for symthesis of glycogen and fat and also functions in excretion.

Hirudinida

Leeches, have no setae, do not have a variable number of segments, they have 34. Possess anterior and posterior suckers. Lack distinct coelomic compartments. Occur predominantly in freshwater habitats. Most are abundant in tropical areas.

Leeches

Usually flattened dorsoventrally and exhibit a variey of patterns and colors (black, brown, red, green). Some are parasites, are hermaphroditic, have a clitellum which only appears during breeding season.

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