Question

In which class of Echinodermata, stalk is found for attachment with substratum?

• A. Asteroidea
• B. Echinoidea
• C. Ophiuroidea
• D. Crinoidea

Answer 1

The correct option is D Crinoidea

Crinoidea is the class of marine animals. Sea lilies are the adult forms of the marine organisms, which are attached by a stalk to the sea bottom. Feather stars or comatulids are the unstalked forms.

The majority of living crinoids are free-swimming and have only a vestigial stalk. In those deep-sea species that still retain a stalk, it may reach up to 1 metre (3.3 ft) in length, although it is usually much smaller. The stalk grows out of the aboral surface, which forms the upper side of the animal in starfish and sea urchins so that crinoids are effectively upside-down by comparison with most other echinoderms. The base of the stalk consists of a disc-like sucker, which, in some species, has root-like structures that further increase its grip on the underlying surface. So, the correct answer is option D.