Question

Choose among the following the characters of Ophiuroidea of phylum Echinodermata:

• A. Madreporite is aboral, tube feet with suckers, open ambulacral grooves
• B. Closed ambulacral grooves, tube feet without suckers, absence of anus
• C. Arms absent, anus is aboral, closed ambulacral grooves
• D. Open ambulacral grooves, tube feet with suckers

Hint:

Ophiuroidea have closed ambulacral grooves, lack suckers on tube feet, and do not have an anus.

Answer 1

The Correct Option is B

Ophiuroidea, commonly called brittle stars, are a class of echinoderms with distinct characteristics:
- Closed ambulacral grooves: Unlike starfish (Asteroidea), their grooves are not open.
- Tube feet without suckers: They move using their arms, not tube feet.
- No anus: Waste is ejected through the mouth.
- Arms are distinct from the central disc and highly flexible.
All these features match option (2).

Answer 2

Ophiuroidea is a class within the phylum Echinodermata, commonly known as brittle stars. The key distinguishing characters of Ophiuroidea are:

1. Closed ambulacral grooves: Unlike starfish (Asteroidea), which have open ambulacral grooves on the oral side of their arms, brittle stars have these grooves closed and covered by plates. This structural difference affects their locomotion and feeding.

2. Tube feet without suckers: The tube feet of Ophiuroidea lack suckers, which are typically present in other echinoderms like starfish. Instead, their tube feet are mainly sensory and help in movement, but do not aid in adhesion to surfaces.

3. Absence of anus: Ophiuroidea have an incomplete digestive system. They possess a mouth but lack an anus, which means the digestive waste is expelled back through the mouth.

These features are quite important as they differentiate Ophiuroidea from other echinoderms and highlight their specialized adaptations.

Thus, the correct characters of Ophiuroidea are: Closed ambulacral grooves, tube feet without suckers, and absence of anus.