They are the only extant organisms that methylate sterols at the 26-position, a fact used to identify the presence of demosponges before their first known unambiguous fossils. They reproduce both sexually and asexually. Some species are brightly colored, with great variety in body shape the largest species are over 1 m (3.3 ft) across. Most are marine dwellers, but one order ( Spongillida) live in freshwater environments. The many diverse orders in this class include all of the large sponges. Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous diatoms. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. Their " skeletons" are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both. They are predominantly leuconoid in structure. They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. They include 76.2% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). The carnivorous ping-pong tree sponge, Chondrocladia lampadiglobus Monanchora arbuscula ( Poecilosclerida) Geodia barretti ( Tetractinellida) Chondrosia reniformis ( Chondrosiida) Spongia officinalis ( Dictyoceratida) Spongilla lacustris ( Spongillida)ĭemosponges (Demospongiae) are the most diverse class in the phylum Porifera. Included are the yellow tube sponge, Aplysina fistularis, the purple vase sponge, Niphates digitalis, the red encrusting sponge, Spiratrella coccinea, and the gray rope sponge, Callyspongia sp.
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