Definition and classification of round worm

Round worm:

The term ‘Round worm’ comes from the Phylum ‘Nemathelminthes’ where round from ‘Nema’ and worm from ‘thelminthes’. Actually the worms under Nemathelminthes are not rounded. The worms are usually elongated, cylindrical, unsegmented with tapering or rounded extremities. But in cross section or transverse section, the worm body appears as circular or rounded. So, the worms under ‘Nemathelminthes’ commonly known as Round worms.

It has a huge class with over a half a million of species. Fortunately, most of them are free living or plant parasites. Majority are parasite to invertebrate host. So, in comparisons, we have only a few veterinary and Medical importance Nematodes.

Classification of Nematodes:

On the basis of presence of phasmid:

Phylum: Nemathelminthes

Class: Nematoda

Sub-class: A. Phasmidia and

     B. Aphasmidia

Phasmids are unicellular sensilia in the lateral tail region of certain species of nematodes. They are similar in their structure to amphid sensilla, but smaller. Phasmid neurons were recently shown to function in modulation of chemorepulsion behavior.

The lateral caudal papillae connected with the lateral precaudal glands. Paired postanal lateral chemoreceptor sensory organs.

1. Subclass: Phasmidia (Secernentea):

Ø  Phasmids are present

Ø   Caudal alae or bursa usually present

Ø   Excretory canal present,

Ø  Cervical and caudal papillae are usually present

Ø   Eggs are without polar plugs.