Earthworm Morphology Short Notes

In this article we will discuss about the earthworm morphology

Earthworm Morphology

• Earthworm is burrowing animal usually live inside the upper layer of moist soil
• Earthworm have long segmented cylindrical body
• Body is divisible into dorsal and ventral regions
  • Dorsal side has a dark mid line along the longitudinal axis is known as dorsal blood vessels
  • Ventral side has prominent genital pores
• Number of segments are 100-120 are called metameres
• First body segment is called the peristomium
• Peristomium possess mouth and fleshy lobe overhanging the mouth is called prostomium
• Last body segment is called the pygidium or anal segment
• 14th, 15th and 16th segments are covered by prominent dark band of glandular tissue called clitellum
• Clitellum divides the body of earthworm in 3 regions
  1. Pre clitellar region – 1st to 13th segments
  2. Clitellar region – 14th to 16th segments
  3. Post clitellar region – 17th and onwards
• All segments except the first, last and clitellum bear S shaped setae, it can be extended or retracted. Their function is locomotion.

Apertures in the body of an earthworm

• Dorsal pores: present after 12 segments except the last segment. Coelomic fluid oozes out from this pore that lubricates the surface of body
• Spermathecal pores: situated ventro-laterally and found in segment 5/6, 6/7, 7/8, 8/9. spermatozoa enter the spermatheca through these pores.
• Female genital pore: present in the 14th segment mid-ventrally. The ova discharged out via the female genital pore
• Male genital pore: situated ventro-laterally in 18th segment. sperm release through this pore.
• Nephridiopores: present in all segments except first two segments. Help for Excretion
• Genital papillae: present in the ventral side of 17 and 19 a pair each. These papillae aids in temporary attachment in course of reproduction