Department of Zoology at ANDC/Zoology Museum/Museum specimens/Annelida/Pheretima

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{|cellpadding="5" cellspacing="6" style="width:100%;background:#FFFFFF; border-style:solid; border-width:3px; border-color:#0066FF;" Date & Time : 28, August 2024      
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=Systematic Position=

Phylum: Annelida

Class: Oligochaeta

Genus: Pheretima

Species: posthuma

Common Name: Earthworm

=Distribution=

Found in moist soil all over the world

=Habit and habitat=

These are nocturnal in habit and live in damp, moist, humus-rich soil of lawns, gardens etc. In dry weather they burrow deeper into the soil to avoid dryness. Their niche is a herbivore and macro-decomposer and is important as a source of food for birds. It also helps in soil aeration and increasing soil fertility.

=Identifying features=


 * Body is long, narrow and cylindrical.
 * Length may reach upto 150 mm.


 * Body colour is brown.


 * Anterior end is pointed while the posterior end is blunt.


 * Body is divided into 100-140 segments called metameres.


 * The anteriormost segment is called Prostomium.


 * Mouth is a crescentic aperture, present at anterior end. The segment containing mouth is called peristomium.


 * Setae are present at all the segments except-1st and last. Each seta is embedded in a setal sac.


 * A glandular band called Clitellum is situated in 14th to 16th segments. It forms coccon during the reproduction.


 * female genital pore is situated in 14th segment (ventral surface)while male genital pore is present in 18th segment.


 * The earthworm feeds on organic matter in the soil.


 * The food is sucked by the pharynx and the oesophageal glands add calcite to neutralise acidity of the soil.


 * The food is then grinded by the horny lining of the gizzard and is absorbed in the intestine.


 * Undigested food material passes out the anus and is deposited as worm castings.


 * The earthworm 'breathes' by the diffusion of gases through its moist skin.


 * The blood contains haemoglobin which transports oxygen throughput the body.


 * Circulatory system is of closed type.


 * Earthworms have no sense organs but they can sense light intensity by small light-sensitive cells found mainly on the uppers skin surface of their body. They can also sense vibrations and chemicals by the means of tactile or chemo-receptors.


 * The earthworms exhibit undulating movement which takes place by alternate contration and relaxation of circular and longitudinal muscles of each segment.
 * Earthworms are hermaphrodites but they reproduce by cross-fertilization.