Phylum Nematoda - General Characters and Classification

Nematoda is sometimes also called as 'Aschelminthes' or 'Nemathelminthes'. The term 'Aschelminthes' (Gr. Askos = cavity; helminth - worm) was proposed by Grobben in 1910, in place of the older name 'Nemathelminthes', which was created by Gagenbaur in 1859 for the unsegmented worms.
A very large heterogeneous group of animals were included under the Aschelminthes. The only reason is that they all possess a peculiar type of body cavity called 'pseudocoel'. But modern Zoologists treat different groups as separate phyla, (upgraded from earlier 'class' level to 'phylum' level), and the name Aschelminthes as a Super phylum or without any taxonomic rank. Nematoda is one of them which is the only major phylum, whereas all others are minor invertebrate phyla.
Nematodes are most familiar forms and second most diverse animal phylum after Arthropoda, with over 15,000 species identified.
Nematodes inhabit all types of habitats from aquatic to terrestrial. They can adapt to the new surroundings rapidly.

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