These are the workhorses of the sponges. The second important cell in sponges are called amoeboid cells. Spicules are made of silica or calcium carbonate. Sponges inhabit every environment, from marine-tropical to polar. There are as many as 15 species in the U.P., Spongilla being the most common genus.
Many sponges have endosymbiont relationships with green algae.
The amoebocytes herd the algae around inside the sponge like cattle. A sponge the size of an eraser can filter 22 L of water a day. Ocean sponges actually filter the entire column of water above them.