Earthworm Morphology Short Notes

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

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