|
Calcareous sponges are a class of the phylum Porifera. They are distinguishable from other classes of sponge in two ways. Under a microscope, a poriferan spicule might be shaped like a three-pointed star, or resembling the letter "Y." Calcareous sponges have spicules resembling four pointed stars. Their chemical makeup is another telltale trait, as their spicules are made mostly of calcium carbonate.
Calcarea are very small compared to other sponges, and indeed only make up 150 of the 15,000 known species of porifera. They only grow to about three or four inches in length, and are solely found in shallow tropical waters. They lack the hollow canal structure of most porifera making them strong despite their size and frail appearance.
|