Question

Antedon is a member of the class
A. Echinoidea
B. Asteroidea
C. Crinoidea
D. Ophiuroidea

Answer 1

Hint: Antedon is a member of the class which has feathery arms and thus are commonly known as sea lilies or feather stars. They are free-living but can also attach to the substratum by specialised appendages on their central disc.

Complete answer:
Antedon is a member of the class Crinoidea. ‘Echinos’ means spiny while ‘dermos’ means skin and thus they are famously known as the spiny skinned animals. All the animals in this Phylum are exclusively marine. Phylum Echinodermata is divided into five classes- Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea and Crinoidea.Additional Information:
Echinoderms generally live at the sea bottom. Some are free swimmers or pelagic while some are sessile i.e attached to the substratum Their body is usually star-shaped, though some are spherical and cylindrical too. This phylum is known for its characteristic ambulacral system or in common terms water vascular system.
Some characteristic features of Antedon are :
-Its body has a central disc-like structure allied to a calyx. It bears five arms and each arm is further bifurcated, bearing a row of lateral extensions known as pinnules. The presence of pinnules gives Antedon a feathery appearance. This is the reason it is commonly known as a feather star too.
-The central disc is differentiated into an oral and aboral surface. The oral surface contains mouth and anus while aboral surface bears arms and cirri. Cirri are unbranched appendages on the central disc and help in its temporary attachment to the substratum.
-Antedon has a great power of autotomy and regeneration.

So, the correct answer is ‘Crinoidea’.

Note: Autotomy is a self-defence method observed in many animals in which they cut off a part of their body( arm in case of Antedon) when attacked by a predator. This gives an illusion that the animal is dead and distracts the predator. The animal takes advantage of this and runs away to protect itself. The deliberate cutting of a part of its body is not harmful to the animal for it has the power to regenerate its lost part.