Question

Which is not a characteristic of class Cestoda?
A. Alimentary canal
B. Embryos with hooks
C. Endoparasitic
D. Three pairs of longitudinal nerve cord

Answer 1

Hint: Platyhelminthes belong to Kingdom Animalia and it includes nearly thirteen thousand species. Cestoda are a class of parasitic worms which belong to the phylum Platyhelminthes.

Complete Answer:
Option A: Cestoda are a class of parasitic flatworms. In cestodes, absence of digestive tracts is seen, thereby meaning absence of alimentary canal. Therefore, this is the correct option.
The worms belonging to Cestoda, absorb the nutrients from the host across the body walls or over the surface of the host’s body.

Option B: The embryos of cestoda have hooks, and they are even sustained as they develop into an adult. In adults, along with hooks, suckers are also seen. Hooks help in penetration of the worm into the intestinal mucosa and suckers help in attaching to the intestinal wall of the host. Therefore, this is the incorrect option.

Option C: The members of Cestoda are commonly known as tapeworms and they are commonly seen as endoparasites. Endoparasites are parasites which live inside the organs and tissues of the host. Therefore, this is the incorrect option.

Option D: In members of Cestoda, three pairs of longitudinal nerve cord are seen. Therefore, this is the incorrect option.

Thus, the correct option is A) Alimentary canal.

Note: The organisms belonging to cestoda are exclusively parasitic and they also have suckers and hookers. Examples include - Taenia spp, convoluta.
A few organisms of these species are seen to cause severe disease like snail fever, etc.