Only about seventeen are of commercial value. Sponges are the most primitive of the multicellular animals, containing neither true tissues nor organs. The outer skin is usually tough permeated by tiny pores through which water is pumped into the sponge in order to filter out the microscopic-sized food. The water is discharged through larger holes.
Sponges come in all size, shapes, and colors.
The average growth is in diameter per year. In the U.S., sponges must be at least five inches when wet to be harvested. Green, yellow, orange, red and purple sponges are frequently found. Most sponges are hermaphrodites, that is, they produce both male and female sex cells. Sponges do not produce eggs until they are at least three years of age.