[113], In the 1990s sponges were widely regarded as a monophyletic group, all of them having descended from a common ancestor that was itself a sponge, and as the "sister-group" to all other metazoans (multi-celled animals), which themselves form a monophyletic group. The scientific term for sponges is Porifera which literally means "pore-bearing." [24], 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. [28], Although the layers of pinacocytes and choanocytes resemble the epithelia of more complex animals, they are not bound tightly by cell-to-cell connections or a basal lamina (thin fibrous sheet underneath). A study in 2005 concluded that mothers teach the behavior to their daughters, and that all the sponge-users are closely related, suggesting that it is a fairly recent innovation.[24]. Sponges are filter feeders. [54] When a gemmule germinates, the archeocytes round the outside of the cluster transform into pinacocytes, a membrane over a pore in the shell bursts, the cluster of cells slowly emerges, and most of the remaining archeocytes transform into other cell types needed to make a functioning sponge. [30], Other types of cell live and move within the mesohyl:[28][30], Many larval sponges possess neuron-less eyes that are based on cryptochromes. Amoebocytes play vital roles in structure, digestion, reproduction, and regeneration of sponges. [28], Some types of cells have a single nucleus and membrane each, but are connected to other single-nucleus cells and to the main syncytium by "bridges" made of cytoplasm. [96] Therefore, they have recently been recognized as the fourth class of sponges.[97][98]. Epidermal cells form the skin on the outside of the sponge. Although a previous publication reported traces of the chemical 24-isopropylcholestane in ancient rocks dating to 1,800 million years ago,[108] recent research using a much more accurately dated rock series has revealed that these biomarkers only appear before the end of the Marinoan glaciation approximately 635 million years ago,[109] and that "Biomarker analysis has yet to reveal any convincing evidence for ancient sponges pre-dating the first globally extensive Neoproterozoic glacial episode (the Sturtian, ~713 million years ago in Oman)". The cave-dwelling predators capture crustaceans under 1 mm (0.039 in) long by entangling them with fine threads, digest them by enveloping them with further threads over the course of a few days, and then return to their normal shape; there is no evidence that they use venom. Some calcified demosponges grow by only 0.2 mm (0.0079 in) per year and, if that rate is constant, specimens 1 m (3.3 ft) wide must be about 5,000 years old. Although there are freshwater species, the great majority are marine (salt-water) species, ranging in habitat from tidal zones to depths exceeding 8,800 m (5.5 mi). The porocytes can contract, thus closing the pores during unfavourable … [42] However, a study in 2007 found no evidence of this and concluded that they extract bacteria and other micro-organisms from water very efficiently (about 79%) and process suspended sediment grains to extract such prey. While it has been argued that this 'sponge biomarker' could have originated from marine algae, recent research suggests that the algae's ability to produce this biomarker evolved only in the Carboniferous; as such, the biomarker remains strongly supportive of the presence of demosponges in the Cryogenian. Sponges are among the simplest of animals. [28] However, experiments have been unable to establish a relationship between the toxicity of chemicals produced by sponges and how they taste to fish, which would diminish the usefulness of chemical defenses as deterrents. Archaeocytes are totipotent cells which can differentiate into other cell types within the body of sponge. [51] A sponge fragment can only regenerate if it contains both collencytes to produce mesohyl and archeocytes to produce all the other cell types. porocyte - cells with pores that allow water into the sponge; they are located all over the sponge's body. epidermal cells - form outer covering; amoeboid cells - wander about, make spicules and skeleton, capture food; collar cells (choanocytes) - create water currents, capture food ; pore cells - surround incurrent pores; Structural features. All freshwater and most shallow-water marine sponges have leuconid bodies. Some sponges overcome this limitation by adopting the "syconoid" structure, in which the body wall is pleated. [104] -eggs are located in the middle layer and they are fertilized. Several sponge species are able to convert coral-derived DOM into sponge detritus,[74][75] and transfer organic matter produced by corals further up the reef food web. , L., Rix, L., Rix, L., Rix, L.,,! For regulating algal-cnidarian symbiosis '' flies, also known as choanocytes ): flagellated cells the... Partially extrude themselves through the osculum creates a vacuum that sucks water in through the osculum engulfing internal... Which connect to the osculum different light regimes now being researched as possible sources of medicines treating. Severe rash in humans who handle them to perform different functions and cells! Epidermis, the genus Aplysina suffer from Aplysina red band syndrome to wait for more favorable conditions or other! 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