BIODIVERSITY - Phylum Annelida

CHARACTERISTICS

"Earthworms"
Body Type: Segmented worms
Symmetry: Bilateral symmetry.
Tissues: Triploblastic.
Body Cavity: Coelomate — true body cavity lined with mesoderm.
Digestive System: Complete — has a mouth and anus.
Circulation: Closed circulatory system (blood confined in vessels).
Respiration: Through skin (cutaneous) or gills in aquatic forms.
Nervous System: Well-developed — ventral nerve cord with simple brain (ganglia).
Excretion: By nephridia.
Reproduction: Mostly sexual, hermaphroditic in many species
Movement: Move using setae (bristle-like structures) or body muscles.
Habitat: Marine, freshwater or moist soil.

CLASSIFICATIONS

Class Oligochaeta

Has a segmented body, a lack of parapodia, a distinct clitellum for reproduction, and the presence of few setae (bristles).
Examples: pheretima, earthworms
Habitat: freshwater, soil, aquatic environment

Class Polychaeta

Has paired, paddle-like appendages called parapodia on most segments, which bear numerous bristle-like structures called chaetae.
Examples: bobbit worm, nereis
Habitat: marine, freshwater

Class Hirudinea

Has a soft, flattened body with an anterior and posterior sucker, a fixed number of 34 segments, and the absence of setae (bristles)
Examples: Leeches
Habitat: Freshwater, aquatic environment, land

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