Question

describe external morphology of earthworm with examples ?

Answer 1

Earthworm

•Reddish brown, terrestrial invertebrate
•Inhabits the upper layer of moist soil
•Lives in burrows made by boring and swallowing the soil
•Can be traced by its worm castings (faecal deposits)
•Common Indian earthworms are Pheretimaand Lumbricus

Answer 2

Answer:

The external features (morphology) of earthworm :

• Earthworms have long, narrow, cylindrical body.
• Their body is divided into short and similar segments.
• These similar segments are known as metameres. They are about 100 to 120 in number.

• These metameres divide body both externally and internally, such type of segmentation is called metameric segmentation or metamerism.
• These segments are separated from each other by distinct ring-like grooves or annuli.

• The dorsal surface of their body is recognised by a dark median/mid-dorsal line, which is in fact a dorsal blood vessel beneath the skin.
• Their ventral surface can be recognised by the presence of genital apertures (pores).

• The earthworms do not possess a distinct head nor any specialised sense organs-like eyes or ears.
• So, the anterior end of these worms consist of mouth and the prostomium.

• Mouth is a crescentric aperture at the anterior end of first segment. This segment is known as peristomium (or buccal segment).

• The dorsal edge of peristomium projects forward above the mouth, as a small fleshy lobe called prostomium which serves as covering for the mouth. It is used as a muscular probe in burrowing. It is also sensory in function.

• Other external features of earthworm include – presence of clitellum, setae and various apertures