Phylum : Annelida
Class : Oligochaeta
Genus : Pheretima
Species : posthuma
· Earthworm is a reddish-brown terrestrial invertebrate that inhabits the upper layer of moist soil.
· During day time, they live in burrows made by boring and swallowing the soil.
· Common Indian earthworms: Pheretima and Lumbricus.
· Earthworms have long segmented cylindrical body.
· Number of segments (metameres): about 100-120.
· Dorsal surface has a dark median mid dorsal line (dorsal blood vessel) along the longitudinal axis of the body.
· First segment (peristomium or buccal segment) bears the mouth. A lobe called prostomium covers the mouth.
· Prostomium is sensory in function and is used to force open cracks in the soil into which the earthworm may crawl.
· In a mature worm, segments 14-16 are covered by a dark band of glandular tissue called clitellum.
· Body has 3 regions: preclitellar, clitellar & postclitellar.
· 4 pairs of spermathecal apertures are found on ventro-lateral sides of intersegmental grooves (5th -9th segments).
· A single female genital pore is present in the mid-ventral line of 14th segment.
· A pair of male genital pores is present on the ventro - lateral sides of the 18th segment.
· Many minute nephridiopores open on the body surface.
· All segments except the first, last and clitellum bear S-shaped setae, embedded in the epidermal pits. Setae can be extended or retracted. Their function is locomotion.