| Number in a sponge |
Multiple ostia may be present on the sponge surface |
Typically, there is one osculum, though large sponges may have multiple oscula |
| Location |
Typically found on the body surface, often in the sponge walls |
Positioned at the apex (top) of the sponge body |
| Function |
· Inflow structures; allow water to enter the sponge
· Water enters through ostia, brings in nutrients and oxygen |
· Outflow structure; expels water from the sponge
· Water that exits through the osculum, carries waste and excessive water |
| Size |
Generally smaller in size |
Larger in size compared to ostia |
| Structure |
Small pores or openings in the sponge body |
Larger opening, often surrounded by a collar or lip |
| Associated cells |
Can be associated with pinacocytes (flattened cells) |
Usually not directly associated with specific cells, but it’s surrounded by the choanoderm or a similar structure |
