Question

(1) Madreporite is absent in
(i) Holothuroidea
(iii) Echinoidea
(ii) Crinoidea
(iv) Asteroidea​

Answer 1

Answer:

Madreporite is absent in Asteroidea.

Answer 2

Madreporite is absent in Holothuroidea. (Option i)

• Unlike most echinoderms where the madreporite connects to the external aquatic environment, the Holothuroidea connect to the coelomic cavity and absorb coelomic fluid instead of seawater.
• Echinoderm water vascular systems contain a light-coloured calcareous opening known as the madreporite, which acts as an equalizer valve.
• There are five main parts to the sea star's water vascular system: the madreporite, the stone canal, the ring canal, the radial canals, the lateral canals, and the tube feet.  
• The ducts are filled with seawater and are used for locomotion, feeding, and respiration.
• By connecting the stone canal with the ring canal around the mouth, the madreporite provides a sieve-like opening for seawater to enter.

#SPJ3