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These sponges are massive or encrusting in form and have a very simple structure with very little variation in spicule form (all spicules tend to be very small). Reproduction is viviparous and the larva is an oval form known as an amphiblastula. This form is usual in calcareous sponges but is less common in other sponges.
Sponges were traditionally distributed in three classes: calcareous sponges (Calcarea), glass sponges (Hexactinellida) and demosponges (Demospongiae). However, studies have now shown that the Homoscleromorpha , a group thought to belong to the Demospongiae , has a genetic relationship well separated from other sponge classes.
The cells in the sponge walls filter food from the water. Whatever is not uptaken by the sponge is pumped through the body out of a large opening. The class demosponges are the most abundant and diverse of the sponge classes. Some of the sponges in this class have skeletons made from silicon-containing spicules, spongin fibers, or both ...
Hexactinellida is one of four classes of phylum Porifera. [4] Hexactinellida can exist in many different forms and shapes: sac, vase, blade, and branching. Hexactinellida is distinguished from the other three classes of sponge for its siliceous skeletal arrangements (spicules), triaxonic symmetry (six-rayed spicules or hexactins), and its huge ...
Water is the medium of the oceans, the medium which carries all the substances and elements involved in the marine biogeochemical cycles. Water as found in nature almost always includes dissolved substances, so water has been described as the "universal solvent" for its ability to dissolve so many substances.
The many diverse orders in this class include all of the large sponges. About 311 million years ago, in the Late Carboniferous , the order Spongillida split from the marine sponges, and is the only sponges to live in freshwater environments. [ 8 ]
Category: Sponges by classification. 3 languages. ... This category lists animals of the phylum Porifera, sorted by taxonomic classes. Subcategories.
Bolosoma stalked glass sponge. Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges.They are usually classified along with other sponges in the phylum Porifera, but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma.