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Flow tank experiments suggest that archaeocyathan morphology allowed them to exploit flow gradients, either by passively pumping water through the skeleton, or, as in present-day, extant sponges, by drawing water through the pores, removing nutrients, and expelling spent water and wastes through the pores into the central space.
Sponges constitute the phylum Porifera, and have been defined as sessile metazoans (multicelled immobile animals) that have water intake and outlet openings connected by chambers lined with choanocytes, cells with whip-like flagella. [13]: 29 However, a few carnivorous sponges have lost these water flow systems and the choanocytes.
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 .
Sponge reefs are reefs produced by sea sponges. All modern sponge reefs are formed by hexactinellid sponges, which have an endoskeleton made of silica spicules and are often referred to as "glass sponges", while historically the non-spiculed, calcite-skeletoned archaeocyathid and stromatoporoid sponges were the primary reef-builders.
All sponges in this class are strictly marine, and, while they are distributed worldwide, most are found in shallow tropical waters. Like nearly all other sponges, they are sedentary filter feeders. All three sponge body plans (asconoid, syconoid, and leuconoid) can be found within the class Calcarea. Typically, calcareous sponges are small ...
Using their ostia and osculum these sponges filter the water for various small aquatic organisms such as protozoans, bacteria, and other free-floating pond life. [4] Sponges of the genus Spongilla partake in symbiotic relationships with green algae, zoochlorellae. The symbiotic zoochlorellae give the sponges a green appearance and without them ...
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] Some species are brightly colored, with great variety in body shape; the largest species are over 1 m (3.3 ft) across. [ 6 ]
Between the pinacocytes, there are the porocytes that allow water into the sponge. Myocytes are small muscular cells that open and close the porocytes. They also form a circular ring around the osculum and help in closing and opening of it. Once through the pores, water travels down canals. The opening to a porocyte is a pore known as an ostium.