Why are ostia important to sponges

Sponges don't have internal organs. They don't have muscles, a nervous system, or a circulatory system. Their walls are lined with many small pores called ostia that allow water flow into the sponge. ... Sponges are able to get microorganisms such as algae and bacteria for food through openings.

The bacterial cell will become turgid.

Explanation:

When a bacterial cell is placed in a solution that has low solute concentration in relation to its cellular contents, such bacteria is said to be placed in an hypotonic solution and as a result, water molecule will move from the solution into the bacterial cell till an equilibrium is reached, making the bacterial cell to become turgid.