Question

In a holothurian respiration occurs by

• A. Tube-feet
• B. Cloacal respiratory tree
• C. Dermal branchiae
• D. Bursae

Answer 1

The correct option is B Cloacal respiratory tree

Sea cucumbers extract oxygen from water in a pair of "respiratory trees" that branch off the cloaca just inside the anus, so that they "breathe" by drawing water in through the anus and then expelling it. The trees consist of a series of narrow tubules branching from a common duct and lie on either side of the digestive tract. Gas exchange occurs across the thin walls of the tubules, to and from the fluid of the main body cavity. Hence, option B is correct.