Demosponge

Demosponges (Demospongiae) are the most diverse <a href="/facts/Class_(biology)/a7MrgFu3">class</a> in the <a href="/facts/Phylum/ELT3Jyax">phylum</a> <a href="/facts/Porifera/E9T2WFWA">Porifera</a>. They include greater than 90% of all species of <a href="/facts/Sponges/E9T2WFWA">sponges</a> with nearly 8,800 species worldwide (World Porifera Database). They are <a href="/facts/Sponge/E9T2WFWA">sponges</a> with a soft body that covers a hard, often massive skeleton made of <a href="/facts/Calcium_carbonate/UQ1wLFna">calcium carbonate</a>, either <a href="/facts/Aragonite/QGcD3SLs">aragonite</a> or <a href="/facts/Calcite/gKMHYQJo">calcite</a>. They are predominantly <a href="/facts/Sponge/E9T2WFWA">leuconoid</a> in structure. Their "<a href="/facts/Skeletons/FXc9Y2lF">skeletons</a>" are made of <a href="/facts/Spicule_(sponge)/tVKvhqID">spicules</a> consisting of fibers of the protein <a href="/facts/Spongin/v5MREx37">spongin</a>, the mineral <a href="/facts/Silica/A3WILp6J">silica</a>, or both. Where spicules of silica are present, they have a different shape from those in the otherwise similar <a href="/facts/Hexactinellida/V3DTVNUl">glass sponges</a>. Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous <a href="/facts/Diatoms/x2oEcP1P">diatoms</a>.
The many diverse <a href="/facts/Order_(biology)/GKLJvIpt">orders</a> in this class include all of the large sponges. About 311 million years ago, in the <a href="/facts/Pennsylvanian_(geology)/Fc1LAJSX">Late Carboniferous</a>, the order <a href="/facts/Spongillida/yk93A0qf">Spongillida</a> split from the marine sponges, and is the only sponges to live in freshwater environments. Some species are brightly colored, with great variety in body shape; the largest species are over 1 m (3.3 ft) across. They reproduce both sexually and <a href="/facts/Asexual_reproduction/HpovW0VS">asexually</a>. They are the only extant organisms that <a href="/facts/Methylate/EvDMWVW5">methylate</a> <a href="/facts/Sterol/QrVlPnWn">sterols</a> at the 26-position, a fact used to identify the presence of demosponges before their first known unambiguous fossils.
Because of many species' long life span (500–1,000 years) it is thought that analysis of the aragonite <a href="/facts/Skeleton/FXc9Y2lF">skeletons</a> of these sponges could extend data regarding <a href="/facts/Ocean_temperature/D9bNcRxX">ocean temperature</a>, <a href="/facts/Salinity/X6mB1YAM">salinity</a>, and other variables farther into the past than has been previously possible. Their dense skeletons are deposited in an organized chronological manner, in concentric layers or bands. The layered skeletons look similar to <a href="/facts/Reef/eHTITdLb">reef</a> <a href="/facts/Coral/j7fBLrpw">corals</a>. Therefore, demosponges are also called coralline sponges.

Demosponge open-in-new

Demosponge