1. Gr. Askos: cavity; helmins: worms. Nema: thread, helmins: worms
2. Habitat: They are marine or freshwater animal.
3. Habit: They are endoparasite.
4. Coelom: Pseudocoelomate which means they have a cavity called pseudocoel between the gut and body wall.
5. Symmetry: bilateral
6. Germ layer; triploblastic
7. Grade of organization: Organ system grade
8. They are non-segmented round worm.
9. Their body is covered with cuticle.
10. Digestive system: simple type
11. The mouth is provided with hooks and suckers
12. Respiratory system: Absent
13. Circulatory system: Absent
14. Nervous system: poorly developed
15. Excretory system: Protonephridia and canals
16. They are unisexual or dioecious animals
17. Reproduction: sexual by gamatic fusion
18. Fertilization: internal

Classification of phylum Aschelminthes/Nemathelminthes

Aschelminthes is classified into five classes

Class 1 Nematoda

(Nema: thread)

• They are endoparasites
• Body is Bilaterally symmetrical and vermiform.
• Body covered in a complex cuticle.
• Sexes are separate
• Examples: Ascaris (round worm), Ancyclostoma (hook worm), Enterobius (pinworm)

Class 2 Rotifera

• They are minute microscopic aquatic
• Sexes are separate
• Excretion: two protonephridia tubes
• Examples: Brachionus, Colotheca, Philodina

Class 3 Gastrotricha

• They are minute aquatic free living
• Sexes are separated or united
• Excretory organ: present or absent
• Examples: Urodasys, macrodasys, Chaetonotus

Class 4 Kinorhyncha

• Minute microscopic marine
• Body is internally segmented
• Sexes are separates
• Development: indirect ( with larval form)
• Examples: Echinoderes, Centroderes

Class 5 Nematomorpha

• They are long slender un-segmented worm
• Known as hair worm
• Sexes are separate
• Examples: Nectonema, Gordius

Phylum Aschelminthes/Nemathelminthes: General characteristics and classification

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