Question

In serpent star, the lower side contains
A) Anus and madreporite
B) Anus only
C) Mouth and madreporite
D) Mouth only

Answer 1

Hint: Serpent star is a species of brittle star in the order Ophiurida. It contains Five large mouth-shield plates on the underside of the disc which surround the central mouth.

Complete Answer:
 A. Anus and madreporite: Madreporite is a light colored calcareous opening. It is used to filter water into the water vascular system of echinoderms. It acts like a pressure-equalizing valve. It's looking like a small wart, on the aboral surface of the central disk of a starfish. The anus is present on the upper side while the madreporite is present on the lower side. Hence option A is incorrect.
B. Anus only: Anus is present on the upper side of the serpent star or aboral surface of the serpent star. Hence option B is incorrect.
C. Mouth and madreporite: The mouth is located on the ventral or lower surface and madreporite is present on the lower surface of the serpent star. Hence option C is correct.
D. Mouth only: The mouth is present in the lower surface. Hence from the given question it seems to be incorrect.

Hence option C: Mouth and madreporite is the correct answer.

Note: The lower side contains mouth and madreporite and upper side contains the anus. The teeth are in a vertical row above each of the five jaws and about five mouth papillae are on each side of the jaw.