Discuss the general characters of phylum aschelminthes or nematoda.

Explanation

General characters of phylum aschelminthes or nematoda are as follows:
(i) The body of nematodes is cylindrical without segment. The symmetry is bilateral in round worms.
(ii) The roundworms are triploblastic.
(iii) The roundworms have organ system level of organization.
(iv) The anterior end does not bear a distinct head. Locomotory appendages of skeleton are absent in roundworms.
(v) A cavity occurs between the body wall and the digestive region. It is not lined by mesothelium.
Therefore, it is called pseudocoelom. It contains pseudocoelomic fluid.
(vi) Digestive tract is complete with mouth as well as anus.
(vii) Respirațion occurs by diffusion through the general body surface.
(viii) The excretory system consists of gland cells or of intracellular canals.
(ix) Sexual dimorphism is present in most of species. Males are smaller than the female, hind end is
curved ventrally. They have penial spicules to aid in copulation. Fertilization is internal. Asexual reproduction is absent.