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The simplest body structure in sponges is a tube or vase shape known as "asconoid", but this severely limits the size of the animal. The body structure is characterized by a stalk-like spongocoel surrounded by a single layer of choanocytes.
The largest biosilica structure on Earth is the giant basal spicule from the deep-sea glass sponge Monorhaphis chuni. [19] The diagram on the right shows: (a) Young specimens of M. chuni anchored to the muddy substratum by one single giant basal spicule (gbs). The body (bo) surrounds the spicule as a continuous, round cylinder.
Like the Homoscleromorpha, calcareous sponges are exclusively viviparous. [7] Calcareous sponges vary from radially symmetrical vase-shaped body types to colonies made up of a meshwork of thin tubes, or irregular massive forms. The skeleton has either a mesh or honeycomb structure of interlocking spicules. [3]
Xestospongia testudinaria is a species of barrel sponge in the family Petrosiidae. More commonly known as Giant Barrel Sponges, they have the basic structure of a typical sponge. Their body is made of a reticulation of cells aggregate on a siliceous scaffold composed of small spikes called spicules.
They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite [citation needed]. They are predominantly leuconoid in structure. Their " skeletons " are made of spicules consisting of fibers of the protein spongin , the mineral silica , or both.
Depending on the body plan of the sponge (which can be asconoid, syconoid, or leuconoid), the spongocoel could be a simple interior space of the sponge or a complexly branched inner structure. Regardless of body plan or class, the spongocoel is lined with choanocytes, which have flagella that push water through the spongocoel, creating a current.
Choanocytes (also known as "collar cells") are cells that line the interior of asconoid, syconoid and leuconoid body types of sponges that contain a central flagellum, or cilium, surrounded by a collar of microvilli which are connected by a thin membrane. They make up the choanoderm, a type of cell layer found in sponges.
The pinacoderm is composed of pinacocytes, flattened epithelial cells that can expand or contract to slightly alter the size and shape of the sponge. [1] It also contains porocytes, oval-shaped cells extending from the pinacoderm to the choanoderm (the body layer containing choanocytes).