Sponge bodies generally lack epithelia but your textbook say

Sponge bodies generally lack epithelia, but your textbook says that researchers have discovered one group of sponges (called the Homoscleromorpha) with some cells arranged in epithelia. Name two specific cellular structures in homoscleromorph bodies (features of single cells, or structures shared in common by adjacent cells) that would convince you that this is true?

Solution

The two unique features of homoscleromorph sponges are,

Both of these structures indicates the presence of a true epithelial layer. The cell adhesion receptors and proteins of homoscleromorphs join the cytoskeletal components such as microfilaments and microtubules of cells. They have septate junctions between ciliated larval cells located adjacently.