Question

stone canal of starfish is-?
A.Reproductive canal
B. Respiratory canal
C. Excretory canal
D. None of the above

Answer 1

Hint: Starfish belongs to the category of echinoderm. It has a water vascular system. In their central canal, they have a central canal and tube-like channels. The water enters by madreporite. The stone canal further circulates it to the ring canal and into the radial canals. The radial canals provide suction to the tube feet by carrying water to the ampullae. So, the stone canal controls the water vascular system and is a part of it.

Complete answer:
> Option A is the reproductive canal. The reproductive system of starfish contains two gonads that release gametes through openings called products, located on each starfish arm, specifically the central disc between the arms. Fertilization in starfish is generally external but in a few species, internal fertilization also takes place.

> Option B is the respiratory canal. The respiration system of Starfish doesn't use gills or lungs to breathe. Their respiration depends on diffusion across surfaces in their body. For example, oxygen is taken up from the water is passed over their tube feet and papulae or skin gills.

> Option C i.e. excretory canal. The Starfish does not have any distinct excretory organs. The waste ammonia is removed by diffusion through the tube feet and papulae.

> Option D i.e none of the above is correct. Because Stone Canal is a tube connecting the sea star's madreporite to its ring canal. It is the second part of the sea star's water vascular system

Hence, The correct answer is option (D).

Additional information:
Stone canal isin is S-shaped and it is characteristic of echinoderms. The stone canal extends downward and opens into a ring canal around the mouth. Stone canal walls are supported by a series of calcareous rings.

Note: Stone canal of starfish takes part in the vascular system. It works as follows- Water enters through the madreporite and flows through the stone canal. It connects to the circular ring canal surrounding the mouth. From here, water flows into five radial canals that branch off the circular ring.