Question

The distinguishing features of a nematode are
a. Pseudocoelom and flame cells
b. Pseudocoelom
c. Flame cells and longitudinal muscle in the body wall
d. Syncytial epidermis and diploblastic nature

Answer 1

Hint: As we know organisms belonging to the phylum Nematoda are known as “roundworms”. These are unsegmented vermiform animals and epidermis has dorsal and ventral nerve cords. Their body is bilaterally symmetrical and triploblastic and is cylindrical in shape. They exhibit tissue level of organization.

Complete answer:
Phylum Nematoda is the only phylum in the animal kingdom which has a presence of pseudocoelom and longitudinal muscle in their body wall. These animals have a body cavity which is developed from the embryonic blastocoel that is not lined with mesoderm.
Pseudocoelom means true coelom is not present. The blastocoel is partly filled by mesodermal cells and the body cavity is lined by mesoderm only towards the body wall and mesoderm is not present towards the gut.
A flame cell is a specialized excretory cell which is found in the simplest freshwater invertebrates, including flatworms and nemerteans, these are the simplest animals to have a dedicated excretory system. Flame cells function like a kidney thereby helping in removal of waste materials. Bundles of flame cells are known as protonephridia. Hence it is not a distinguishing feature of a nematode.
Syncytial epidermis is found in the body wall of Ascaris. Syncytium is a multinucleate cell that is formed from multiple nuclear divisions. Hence not a distinguishing feature of a nematode.
Diploblastic means having a body that is derived from only two embryonic cell layers which is ectoderm and endoderm, but no mesoderm, as in sponges and coelenterates.

Hence the correct answer is option B which is Pseudocoelom.

Note:
The alimentary canal of nematode is distinct, with the presence of mouth and the anus. They are sexually dimorphic in nature. They are devoid of the circulatory system and the respiratory system. They can be free-living or parasitic in nature. Their epidermis is said to be synctical and contains dorsal or ventral nerve cords. Their body-wall muscles are longitudinal and possess amoeboid sperm cells.