Question

Which of the following statements about all the four of Spongilla, leech, dolphin and penguin is correct?

• A. Penguin is homoiothermic while the remaining three are poikilothermic.
• B. Leech is a fresh water form while all others are marine.
• C. Spongilla has special collared cells called choanocytes, not found in the remaining three.
• D. All are bilaterally symmetrical.

Answer 1

The correct option is C Spongilla has special collared cells called choanocytes, not found in the remaining three.

Choanocytes are cells that line the interior of asconoid, syconoid and leuconoid body type sponges that contain a central flagellum, or undulipodia, surrounded by a collar of microvilli which are connected by a thin membrane. They make up Choanoderm, a type of cell layer found in sponges.

By cooperatively moving their flagella, choanocytes generate a flow of water through the sponges pores, into the spongocoel, and out through the osculum. This improves both respiratory and digestive functions for the sponge, pulling in oxygen and nutrients and allowing a rapid expulsion of carbon dioxide and other waste products. Although all cells in a sponge are capable of living on their own, choanocytes carry out most of the sponge's ingestion, passing digested materials to the amoebocytes for delivery to other cells.

So the correct option is 'Spongilla has special collared cells called choanocytes, not found in the remaining three'.