Question

Which of the following endoparasites of humans does show viviparity?
A. Trichinella spiralis
B. Ascaris lumbricoides
C. Ancylostoma duodenale
D. Enterobius vermicularis

Answer 1

Nematodes belong to the phylum nematoda. They are found inhabiting a wide range of environments. These are in general ovoviviparous, that is some of the nematodes are egg laying while certain parasitic nematodes give birth by producing larvae therefore they are known to exhibit viviparity also.

Complete answer:
A nematode parasite, called Trichinella spiralis is found to occur in pigs, bears, horses, rodents and humans. It is the causative agent of a disease known as trichinosis. In humans, Trichinella spiralis is the smallest identified nematode parasite. The size of male in length ranges in between 1.4mm to 1.6mm while the size of female is double as compared to the size of the males. The anterior side of the body is more slender than the posterior side. In females, hatching of the larvae occurs at the anterior side while the posterior side contains the developing eggs.
On the other hand, Ascaris lumbricoides, Ancylostoma duodenale and Enterobius vermicularis are endoparasites which lay eggs.

Hence, the correct answer is option (A).

Note: Trichinella spiralis is a nematode parasite responsible for causing a disease known as trichinosis which is often characterized by pain in muscles and soreness. Spread of larvae is carried out via consumption of the infected flesh of larvae parasites by another host. Trichinella spiralis is most commonly found in uncooked pork as well as various products based on pork therefore it is also known as the “pork worm”.