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About|the aquatic animal|the porous cleaning tool|Sponge (material)|other uses|Sponge (disambiguation)Good articleAutomatic taxobox| name = Sponge| taxon = Porifera| oldest fossil = Ediacaran| image =SpongeColorCorrect.jpg| image_width = 250px| authority = Robert Edmund Grant|Grant in Robert Bentley Todd|Todd , 1836| subdivision ranks = Included groups| display children = 1 Sponges are animal s of the phylum Porifera (IPAc-en|icon|p|?|'|r|?|f|?r|?; meaning "pore bearer"). Their bodies, which are full of pores and channels allowing water to circulate through them, consist of jelly-like mesohyl sandwiched between two thin layers of Cell (biology)|cell s. While all animals have unspecialized cells that can transform into specialized cells, sponges are unique in having some specialized cells, but can also have specialized cells that can transform into other types, often migrating between the main cell layers and the mesohyl in the process. Sponges do not have nervous system|nervous , digestive system|digestive or circulatory system s. Instead, most rely on maintaining a constant water flow through their bodies to obtain food, oxygen and remove wastes. The shapes of their bodies are adapted for maximal efficiency of water flow. Water enters through the central cavity, deposits nutrients, and leaves through a hole called the osculum . All sponges are Sessility (zoology)|sessile aquatic animals. Although there are freshwater species, the great majority are marine (salt water) species, ranging from tidal zones to depths exceeding convert|8800|m|mi.
While most of the approximately 5,000–10,000& nbsp;known species feed on bacteria and other food particles in the water, some host photosynthesis|photosynthesizing micro-organisms as endosymbiont s and these alliances often produce more food and oxygen than they consume. A few species of sponge that live in food-poor environments have become carnivore s that prey mainly on small crustacean s.cite journal | author=J. Vacelet and E. Duport | title=Prey capture and digestion in the carnivorous sponge Asbestopluma hypogea (Porifera: Demospongiae) |url= http://www.springerlink.com/content/bwlbj547br0qb4fq/
Most species use sexual reproduction , releasing sperm cells into the water to fertilize ovum|ova that in some species are released and in others are retained by the "mother". The fertilized eggs form larva e which swim off in search of places to settle. Sponges are known for regenerating from fragments that are broken off, although this only works if the fragments include the right types of cells. A few species reproduce by budding. When conditions deteriorate, for example as temperatures drop, many freshwater species and a few marine ones produce gemmule s, "survival pods" of unspecialized cells that remain dormant until conditions improve and then either form completely new sponges or recolonize the skeletons of their parents.
The mesohyl functions as an endoskeleton in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks. More commonly, the mesohyl is stiffened by Biomineralization|mineral sponge spicule|spicules , by spongin fibers or both. Demosponge s use spongin, and in many species, silica spicules and in some species, calcium carbonate exoskeleton s. Demosponges constitute about 90% of all known sponge species, including all freshwater ones, and have the widest range of habitats. Calcareous sponge s, which have calcium carbonate spicules and, in some species, calcium carbonate exoskeletons, are restricted to relatively shallow marine waters where production of calcium carbonate is easiest. The fragile glass sponge s, with " scaffolding " of silica spicules, are restricted to polar regions and the ocean depths where predators are rare. Fossils of all of these types have been found in rocks dated from ma|580. In addition Archaeocyathid s, whose fossils are common in rocks from ma|530|490, are now regarded as a type of sponge.
The sponge's closest unicellular|single-celled relatives are thought to be choanoflagellate s, which strongly resemble the cells sponges use to drive their water flow systems and capture most of their food. Sponges are generally agreed, also, to not form a monophyletic group, in other words do not include all and only the descendants of a common ancestor, because Eumetazoa (more complex animals) are thought to be descendants of a subgroup of sponges. However it is uncertain which group of sponges is closest to Eumetazoa, as both calcareous sponges and a subgroup of demosponges called Homoscleromorpha have been nominated by different researchers. In addition, a study in 2008 suggested the earliest animals may have been similar to modern Ctenophora|comb jellies .
The few species of demosponge that have entirely soft fibrous skeletons with no hard elements have been used by humans over thousands of years for several purposes, including as padding and as cleaning tools. By the 1950s, though, these had been overfished so heavily that the industry almost collapsed, and most sponge-like materials are now synthetic. Sponges and their microscopic endosymbionts are now being researched as possible sources of medicines for treating a wide range of diseases. Dolphins have been observed using sponges as tools while foraging.
Distinguishing features
See| Cnidaria | Ctenophore Sponges constitute the phylum Porifera, and have been defined as Sessility (zoology)|sessile metazoa ns (multi-celled animals) that have water intake and outlet openings connected by chambers lined with choanocyte s, cells with whip-like flagella. However, a few carnivorous sponges have lost these water flow systems and the choanocytes.Cite book | author=Hooper, J. N. A., Van Soest, R. W. M., and Debrenne, F. | contribution=Phylum Porifera Grant, 1836 | pages=9–14 | editor=Hooper, J. N. A., and Van Soest, R. W. M. | title=Systema Porifera: A Guide to the Classification of Sponges | publisher=Kluwer Academic/Plenum | location=New York | year=2002 | url= http://books.google.com/? id=OQoxzqjQXWEC& pg=PA220& dq=sponge+attachment+substrate | accessdate=2008-11-06 | isbn=9780306472602 All known living sponges can remold their bodies, as most types of their cells can move within their bodies and a few can change from one type to another.
Like cnidaria ns (jellyfish, etc.) and ctenophore s (comb jellies), and unlike all other known metazoans, sponges' bodies consist of a non-living jelly-like mass sandwiched between two main layers of cells.cite book | author=Hinde, R. T., | year=1998 | chapter=The Cnidaria and Ctenophora | pages=28–57 | editor=Anderson, D.T., | title=Invertebrate Zoology | publisher=Oxford University Press | isbn=0195513681 Cnidarians and ctenophores have simple nervous systems, and their cell layers are bound by internal connections and by being mounted on a basement membrane (thin fibrous mat, also known as " basal lamina "). Sponges have no nervous systems, their middle jelly-like layers have large and varied populations of cells, and some types of cell in their outer layers may move into the middle layer and change their functions.
& nbsp; !! Spongescite book !& #33; Cnidarian s and ctenophore s
Nervous system
Cells in each layer bound together
Number of cells in middle "jelly" layer
Cells in outer layers can move inwards and change functions
Basic structure
Cell types
Annotated image/Porifera cell typesA sponge's body is hollow and is held in shape by the mesohyl , a jelly-like substance made mainly of collagen and reinforced by a dense network of fibers also made of collagen. The inner surface is covered with choanocyte s, cells with cylindrical or conical collars surrounding one flagellum per choanocyte. The wave-like motion of the whip-like flagella drives water through the sponge's body. All sponges have wikt:ostium|ostia , channels leading to the interior through the mesohyl, and in most sponges these are controlled by tube-like porocytes that form closable inlet valves. Pinacocyte s, plate-like cells, form a single-layered external skin over all other parts of the mesohyl that are not covered by choanocytes, and the pinacocytes also digest food particles that are too large to enter the ostia, while those at the base of the animal are responsible for anchoring it.
Other types of cell live and move within the mesohyl:
Lophocyte s are amoeba -like cells that move slowly through the mesohyl and secrete collagen fibres.
Collencyte s are another type of collagen-producing cell.
Rhabdiferous cells secrete polysaccharide s that also form part of the mesohyl.
Oocyte s and spermatocyte s are reproductive cells.
Sclerocyte s secrete the mineralized sponge spicule|spicules ("little spines") that form the skeleton s of many sponges and in some species provide some defense against predators.
In addition to or instead of sclerocytes, demosponge s have spongocyte s that secrete a form of collagen that polymer izes into spongin , a thick fibrous material that stiffens the mesohyl.
Myocyte s ("muscle cells") conduct signals and cause parts of the animal to contract.
"Grey cells" act as sponges' equivalent of an immune system .
Archaeocytes (or amoebocytes ) are amoeba -like cells that are totipotent , in other words each is capable of transformation into any other type of cell. They also have important roles in feeding and in clearing debris that block the ostia.
Glass sponges' syncytia
Annotated image/Euplectella | float=left Glass sponge s present a distinctive variation on this basic plan. Their spicules, which are made of silica , form a scaffolding -like framework between whose rods the living tissue is suspended like a cobweb that contains most of the cell types. This tissue is a syncytium that in some ways behaves like many cells that share a single external Cell membrane|membrane , and in others like a single cell with multiple cell nucleus|nuclei . The mesohyl is absent or minimal. The syncytium's cytoplasm , the soupy fluid that fills the interiors of cells, is organised into "rivers" that transport nuclei, organelle s ("organs" within cells) and other substances.cite journal | author=Leys, S. P. | title=The significance of syncytial tissues for the position of the Hexactinellida in the Metazoa | journal=Integrative and Comparative Biology | issue=1| pages=19–27| doi=10.1093/icb/43.1.19 | year=2003 | volume=43 | pmid=21680406 Instead of choanocytes they have further syncytia, known as choanosyncytia, which form bell-shaped chambers which water enters via perforations. The insides of these chambers are lined with "collar bodies", each consisting of a collar and flagellum but without a nucleus of its own. The motion of the flagella sucks water through passages in the "cobweb" and expels it via the open ends of the bell-shaped chambers.
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 . The sclerocyte s that build spicules have multiple nuclei, and in glass sponge larvae they are connected to other tissues by cytoplasm bridges; such connections between sclerocytes have not so far been found in adults, but this may simply reflect the difficulty of investigating such small-scale features. The bridges are controlled by "plugged junctions" that apparently permit some substances to pass while blocking others. Clear
Water flow and body structures
Annotated image/Porifera body structuresMost sponges work rather like chimney s: they take in water at the bottom and eject it from the osculum ("little mouth") at the top. Since ambient currents are faster at the top, the suction effect that they produce does some of the work for free. Sponges can control the water flow by various combinations of wholly or partially closing the osculum and ostia (the intake pores) and varying the beat of the flagella, and may shut it down if there is a lot of sand or silt in the water.
Although the layers of pinacocyte s and choanocyte s 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). The flexibility of these layers and re-modeling of the mesohyl by lophocytes allow the animals to adjust their shapes throughout their lives to take maximum advantage of local water currents.
The simplest body structure in sponges is a tube or vase shape known as " asconoid ", but this severely limits the size of the animal. If it is simply scaled up, the ratio of its volume to surface area increases, because surface increases as the square of length or width while volume increases proportionally to the cube. The amount of tissue that needs food and oxygen is determined by the volume, but the pumping capacity that supplies food and oxygen depends on the area covered by choanocytes. Asconoid sponges seldom exceed convert|1|mm|in in diameter.
Some sponges overcome this limitation by adopting the " syconoid " structure, in which the body wall is pleat ed. The inner pockets of the pleats are lined with choanocytes, which connect to the outer pockets of the pleats by ostia. This increase in the number of choanocytes and hence in pumping capacity enables syconoid sponges to grow up to a few centimeters in diameter. The "leuconid" pattern boosts pumping capacity further by filling the interior almost completely with mesohyl that contains a network of chambers lined with choanocytes and connected to each other and to the water intakes and outlet by tubes. Leuconid sponges grow to over convert|1|m|ft in diameter, and the fact that growth in any direction increases the number of choanocyte chambers enables them to take a wider range of forms, for example "encrusting" sponges whose shapes follow those of the surfaces to which they attach. All freshwater and most shallow-water marine sponges have leuconid bodies. The networks of water passages in glass sponge s are similar to the leuconid structure. In all three types of structure the cross-section area of the choanocyte-lined regions is much greater than that of the intake and outlet channels. This makes the flow slower near the choanocytes and thus makes it easier for them to trap food particles. For example in Leuconia , a small leuconoid sponge about convert|10|cm|in tall and convert|1|cm|in in diameter, water enters each of more than 80,000 intake canals at 6& nbsp;cm per minute . However, because Leuconia has more than 2& nbsp;million flagellated chambers whose combined diameter is much greater than that of the canals, water flow through chambers slows to 3.6& nbsp;cm per hour , making it easy for choanocytes to capture food. All the water is expelled through a single osculum at about 8.5& nbsp;cm per second , fast enough to carry waste products some distance away.cite book | author=C. Hickman, C .P. (Jr.), Roberts, L. S., and Larson, A. | year=2001 | title= Integrated Principles of Zoology | edition=11 | publisher=McGraw-Hill | location=New York | isbn=9780072909616 | page=247
In zoology a skeleton is any fairly rigid structure of an animal, irrespective of whether it has joints and irrespective of whether it is biomineralization|biomineralized . The mesohyl functions as an endoskeleton in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks. More commonly the mesohyl is stiffened by mineral sponge spicule|spicules , by spongin fibers or both. Spicules may be made of silica or calcium carbonate , and vary in shape from simple rods to three-dimensional "stars" with up to six rays. Spicules are produced by sclerocyte cells, and may be separate, connected by joints, or fused.
Some sponges also secrete exoskeleton s that lie completely outside their organic components. For example sclerosponge s ("hard sponges") have massive calcium carbonate exoskeletons over which the organic matter forms a thin layer with choanocyte chambers in pits in the mineral. These exoskeletons are secreted by the pinacocyte s that form the animals' skins. Clear
Classes
Sponges are divided into Class (biology)|classes mainly according to the composition of their skeleton s:
& nbsp; !! Type of cellscite book !& #33; Sponge spicule|Spicules !& #33; Spongin fibers !& #33; Massive exoskeleton !& #33; Body form
Calcarea
Glass sponge s
Demosponge s
Vital functions
Movement
Although adult sponges are fundamentally Sessility (zoology)|sessile animals, some marine and freshwater species can move across the bottom at speeds of convert|1|-|4|mm|in per day, as a result of amoeba (genus)|amoeba -like movements of pinacocyte s and other cells. A few species can contract their whole bodies, and many can close their osculum|oscula and wikt:ostium|ostia .
Respiration, feeding and excretion
Sponges do not have distinct circulatory , respiratory , digestive , and excretory systems – instead the water flow system supports all these functions. They filter feeding|filter food particles out of the water flowing through them. Particles larger than 50& nbsp;micrometers cannot enter the wikt:ostium|ostia and pinacocyte s consume them by phagocytosis (engulfing and internal digestion). Particles from 0.5& nbsp;µm to 50& nbsp;µm are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by archaeocyte s which partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5& nbsp;micrometers, pass through the ostia and are caught and consumed by choanocyte s. Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge's food supply.Cite book | contribution=Porifera (Sponges) | author=Bergquist, P. R. | title=Encyclopedia of Life Sciences | year=2001 | publisher= John Wiley & Sons, Ltd. | doi=10.1038/npg.els.0001582 Archaeocytes transport food packaged in Vesicle (biology)|vesicle s from cells that directly digest food to those that do not. At least one species of sponge has internal fibers that function as tracks for use by nutrient-carrying archaeocytes, and these tracks also move inert objects.
It used to be claimed that glass sponge s could live on nutrients dissolved in sea water and were very averse to silt.cite journal | author=Krautter, M. | title=Ecology of siliceous sponges: Application to the environmental interpretation of the Upper Jurassic sponge facies (Oxfordian) from Spain | journal=Cuadernos de Geología Ibérica | year=1998 | volume=24 | pages=223–239 | issn=0378-102X | url= http://www.ucm.es/BUCM/revistas/geo/16986180/articulos/JIGE9898110223A.PDF |format=PDF| accessdate=2008-11-10 Dead link|date=September 2010|bot=H3llBot 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.cite journal | doi=10.4319/lo.2007.52.1.0428 | author=Yahel, G., Whitney, F., Reiswig, H. M., Eerkes-Medrano, D. I., and Leys, S.P. | date= April 20, 2007 | title=In situ feeding and metabolism of glass sponges (Hexactinellida, Porifera) studied in a deep temperate fjord with a remotely operated submersible | journal=Limnology and oceanography | volume=52 | issue=1 | pages=428–440 | issn=0024-3590 | url= http://cat.inist.fr/? aModele=afficheN& cpsidt=18876170 | accessdate=2008-11-02 Collar bodies digest food and distribute it wrapped in vesicles that are transported by dynein "motor" molecules along bundles of microtubule s that run throughout the syncytium .
Sponges' cells absorb oxygen by diffusion from the water flow system, into which carbon dioxide and other soluble waste products such as ammonia also diffuse. Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons.
Carnivorous sponges
A few species that live in waters where the supply of food particles is very poor prey on crustacea ns and other small animals. Most belong to the family (biology)|family Cladorhizidae , but a few members of the Guitarridae and Esperiopsidae are also carnivores. In most cases little is known about how they actually capture prey, although some species are thought to use either sticky threads or hooked sponge spicule|spicules .cite journal | author=Watling, L. | title=Predation on copepods by an Alaskan cladorhizid sponge | journal=Journal of the Marine Biological Association of the UK | year=2007| volume=87| pages=1721–1726 | doi=10.1017/S0025315407058560 | issue=6 Most carnivorous sponges live in deep waters, up to convert|8840|m|mi,cite journal | author=Vacelet, J., and Boury-Esnault, N. | title=Carnivorous sponges | journal=Nature | volume=373 | pages=333–335 | month=January | year=1995 | doi=10.1038/373333a0 | issue=6512 and the development of deep-ocean exploration techniques is expected to lead to the discovery of several more.cite journal | author=Vacelet, J. | title=A new genus of carnivorous sponges (Porifera: Poecilosclerida, Cladorhizidae) from the deep N-E Pacific, and remarks on the genus Neocladia | journal=Zootaxa | volume=1752 | pages=57–65 | year=2008 | url= http://www.mapress.com/zootaxa/2008/f/z01752p065f.pdf |format=PDF| accessdate=2008-10-31 However one species has been found in Mediterranean caves at depths of convert|17|-|23|m|ft, alongside the more usual filter feeding sponges. The cave-dwelling predators capture crustaceans under convert|1|mm|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 .
Most known carnivorous sponges have completely lost the water flow system and choanocyte s. However the genus Chondrocladia uses a highly modified water flow system to inflate balloon-like structures that are used for capturing prey.cite journal | author=Vacelet, J., and Kelly, M. | title=New species from the deep Pacific suggest that carnivorous sponges date back to the Early Jurassic | journal=Nature Precedings | month=September | year=2008 | url= http://precedings.nature.com/documents/2327/version/1 | accessdate=2008-10-31 | doi=10.1038/npre.2008.2327.1 | doi_brokendate=2010-03-19
Endosymbionts
Freshwater sponges often host green algae as endosymbiont s within archaeocyte s and other cells, and benefit from nutrients produced by the algae. Many marine species host other photosynthesis|photosynthesizing organisms, most commonly cyanobacteria but in some cases dinoflagellate s. Symbiotic cyanobacteria may form a third of the total mass of living tissue in some sponges, and some sponges gain 48% to 80% of their energy supply from these micro-organisms. In 2008 a University of Stuttgart team reported that spicule s made of silica conduct light into the mesohyl , where the photosynthesizing endosymbionts live.News report at cite journal | author=Brümmer, F., Pfannkuchen, M., Baltz, A., Hauser, T., and Thiel, V. | title=Light inside sponges | journal=Journal of Experimental Marine Biology and Ecology | volume=367| issue=2| pages=61–64 | doi=10.1016/j.jembe.2008.06.036 | year=2008 . News report at cite news | title=Nature's 'fibre optics' experts | publisher=BBC | url= http://news.bbc.co.uk/2/hi/science/nature/7720836.stm | accessdate=2008-11-10 | date=2008-11-10. Sponges that host photosynthesizing organisms are most common in waters with relatively poor supplies of food particles, and often have leafy shapes that maximize the amount of sunlight they collect.
A recently-discovered carnivorous sponge that lives near hydrothermal vent s hosts Methanotrophic|methane-eating bacteria, and digests some of them.
"Immune" system
Sponges do not have the complex immune system s of most other animals. However they reject Medical grafting|grafts from other species but accept them from other members of their own species. In a few marine species, gray cells play the leading role in rejection of foreign material. When invaded, they produce a chemical that stops movement of other cells in the affected area, thus preventing the intruder from using the sponge's internal transport systems. If the intrusion persists, the grey cells concentrate in the area and release toxins that kill all cells in the area. The "immune" system can stay in this activated state for up to three weeks.
Reproduction
Asexual
Sponges have three asexual reproduction|asexual methods of reproduction: after fragmentation; by budding ; and by producing gemmule s. Fragments of sponges may be detached by currents or waves. They use the mobility of their pinacocyte s and choanocyte s and reshaping of the mesohyl to re-attach themselves to a suitable surface and then rebuild themselves as small but functional sponges over the course of several days. The same capabilities enable sponges that have been squeezed through a fine cloth to regenerate. A sponge fragment can only regenerate if it contains both collencyte s to produce mesohyl and archeocyte s to produce all the other cell types. A very few species reproduce by budding.
Gemmules are "survival pods" which a few marine sponges and many freshwater species produce by the thousands when dying and which some, mainly freshwater species, regularly produce in autumn. Spongocyte s make gemmules by wrapping shells of spongin , often reinforced with spicule s, round clusters of archeocyte s that are full of nutrients. Freshwater gemmules may also include phytosynthesizing symbionts.cite book | author=Smith, D. G., and Pennak, R. W. | title=Pennak's Freshwater Invertebrates of the United States: Porifera to Crustacea | publisher=John Wiley and Sons | year=2001 | isbn=0471358371 | pages=47–50 | edition=4 | url= http://books.google.com/? id=GqIctb8IqPoC& pg=PA48& lpg=PA48& dq=sponge+gemmule | accessdate=2008-10-31 The gemmules then become dormant, and in this state can survive cold, drying out, lack of oxygen and extreme variations in salinity . Freshwater gemmules often do not revive until the temperature drops, stays cold for a few months and then reaches a near-"normal" level. When a gemmule germinates, the archeocytes round the outside of the cluster transform into pinacocyte s, 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. Gemmules from the same species but different individuals can join forces to form one sponge. Some gemmules are retained within the parent sponge, and in spring it can be difficult to tell whether an old sponge has revived or been "recolonized" by its own gemmules.
Sexual
Most sponges are hermaphrodite s (function as both sexes simultaneously), although sponges have no gonad s (reproductive organs). Sperm are produced by choanocyte s or entire choanocyte chambers that sink into the mesohyl and form spermatic cyst s while eggs are formed by transformation of archeocyte s, or of choanocytes in some species. Each egg generally acquires a yolk by consuming "nurse cells". During spawning, sperm burst out of their cysts and are expelled via the osculum . If they contact another sponge of the same species, the water flow carries them to choanocytes that engulf them but, instead of digesting them, metamorphose to an ameboid form and carry the sperm through the mesohyl to eggs, which in most cases engulf the carrier and its cargo.
A few species release fertilized eggs into the water, but most retain the eggs until they hatch. There are four types of larvae, but all are balls of cells with an outer layer of cells whose flagella e or cilia enable the larvae to move. After swimming for a few days the larvae sink and crawl until they find a place to settle. Most of the cells transform into archeocytes and then into the types appropriate for their locations in a miniature adult sponge.
Glass sponge embryos start by dividing into separate cells, but once 32& nbsp;cells have formed they rapidly transform into larvae that externally are ovoid with a band of cilia round the middle that they use for movement, but internally have the typical glass sponge structure of spicules with a cobweb-like main syncitium draped around and between them and choanosyncytia with multiple collar bodies in the center. The larvae then leave their parents' bodies.cite journal | author=Leys, S., Cheung, E., and Boury-Esnault, N. | title=Embryogenesis in the glass sponge Oopsacas minuta : Formation of syncytia by fusion of blastomeres | journal=Integrative and Comparative Biology | year=2006 | volume=46 | issue=2 | pages=104–117 | doi=10.1093/icb/icj016 | pmid=21672727
Life cycle
Sponges in temperate regions live for at most a few years, but some Tropics|tropical species and perhaps some deep-ocean ones may live for 200& nbsp;years or more. Some calcified demosponge s grow by only convert|0.2|mm|in per year and, if that rate is constant, specimens convert|1|m|ft wide must be about 5,000& nbsp;years old. Some sponges start sexual reproduction when only a few weeks old, while others wait until they are several years old.
Coordination of activities
Adult sponges lack neuron s or any other kind of nervous tissue . However most species have the ability to perform movements that are coordinated all over their bodies, mainly contractions of the pinacocyte s, squeezing the water channels and thus expelling excess sediment and other substances that may cause blockages. Some species can contract the osculum independently of the rest of the body. Sponges may also contract in order to reduce the area that is vulnerable to attack by predators. In cases where two sponges are fused, for example if there is a large but still unseparated bud, these contraction waves slowly become coordinated in both of the " Siamese twins ". The coordinating mechanism is unknown, but may involve chemicals similar to neurotransmitter s.cite journal | author=Nickel, M. | title=Kinetics and rhythm of body contractions in the sponge Tethya wilhelma (Porifera: Demospongiae) | journal=Journal of Experimental Biology | volume=207 | pages=4515–4524 | month=December | year=2004 | doi=10.1242/jeb.01289 | pmid=15579547 | issue=Pt 26 However glass sponge s rapidly transmit electrical impulses through all parts of the syncytium , and use this to halt the motion of their flagella if the incoming water contains toxins or excessive sediment. Myocyte s are thought to be responsible for closing the osculum and for transmitting signals between different parts of the body.
Sponges contain gene s very similar to those that contain the "recipe" for the post- synaptic density, an important signal-receiving structure in the neurons of all other animals. However in sponges these genes are only activated in "flask cells" that appear only in larvae and may provide some sensory capability while the larvae are swimming. This raises questions about whether flask cells represent the predecessors of true neurons or are evidence that sponges' ancestors had true neurons but lost them as they adapted to a sessile lifestyle.cite journal | author=Sakarya, O., Armstrong, K. A., Adamska, M., Adamski, M., Wang, I., et al. | year=2007 | title=A Post-Synaptic Scaffold at the Origin of the Animal Kingdom | journal=PLoS ONE | volume=2 | issue=6 | doi=10.1371/journal.pone.0000506 | pages=e506 | pmid=17551586 | pmc=1876816 | editor1-last=Vosshall | editor1-first=Leslie
Ecology
Habitats
Sponges are worldwide in their distribution, from the polar regions to the tropics. Most live in quiet, clear waters, because sediment stirred up by waves or currents would block their pores, making it difficult for them to feed and breathe. The greatest numbers of sponges are usually found on firm surfaces such as rocks, but some sponges can attach themselves to soft sediment by means of a root-like base.cite journal | author=Weaver, J. C., Aizenberg, J., and Fantner, G .E. et al. | title=Hierarchical assembly of the siliceous skeletal lattice of the hexactinellid sponge Euplectella aspergillum | journal=Journal of Structural Biology | volume=158 | issue=1 | month=April | year=2007| pages=93–106 | doi = 10.1016/j.jsb.2006.10.027 | pmid=17175169
Sponges are more abundant but less diverse in temperate waters than in tropical waters, possibly because organisms that prey on sponges are more abundant in tropical waters.cite journal | author=Ruzicka, R., and Gleason, D. F. | title=Latitudinal variation in spongivorous fishes and the effectiveness of sponge chemical defenses | journal=Oecologia | year=2008| volume=154 | pages=785–794 | doi=10.1007/s00442-007-0874-0 | url= http://www.bio.georgiasouthern.edu/Bio-home/Gleason/Ruzicka& Gleasonfulltext.pdf |format=PDF| accessdate=2008-11-11 | pmid=17960425 | issue=4 Glass sponge s are the most common in polar waters and in the depths of temperate and tropical seas, as their very porous construction enables them to extract food from these resource-poor waters with the minimum of effort. Demosponge s and Calcarea|calcareous sponges are abundant and diverse in shallower non-polar waters. cite book | author=Gage, J. D., and Tyler, P. A. | title=Deep-sea Biology: A Natural History of Organisms at the Deep-Sea Floor | publisher=Cambridge University Press | year=1996 | isbn=0521336651 | pages=91–93 | url= http://books.google.com/? id=kHZO5igKhsAC& dq=sponge+porifera+geographical+distribution+temperature | accessdate=2008-11-11
The different Class (biology)|classes of sponge live in different ranges of habitat: Clear
& nbsp; !! Water type !! Depth !! Type of surface
Calcarea
Glass sponge s
Demosponge s
As primary producers
Sponges with photosynthesis|photosynthesizing endosymbiont s produce up to three times more oxygen than they consume, as well as more organic matter than they consume. Such contributions to their habitats' resources are significant along Australia 's Great Barrier Reef but relatively minor in the Caribbean.
Defenses
Many sponges shed spicule s, forming a dense carpet several meters deep that keeps away echinoderm s which would otherwise prey on the sponges. They also produce toxins that prevent other sessile organisms such as bryozoa ns or sea squirt s from growing on or near them, making sponges very effective competitors for living space. One of many examples includes ageliferin .
A few species, such as the Caribbean fire sponge Tedania ignis , cause a severe rash in humans who handle them. Turtles and some fish feed mainly on sponges. It is often said that sponges produce chemical defenses against such predators. However an experiment showed that there is no 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. Predation by fish may even help to spread sponges by detaching fragments.
Glass sponge s produce no toxic chemicals, and live in very deep water where predators are rare.
Predation
Sponge flies, also known as spongilla-flies ( Neuroptera , Sisyridae ), are specialist predators of freshwater sponges. The female lays her eggs on vegetation overhanging water. The larvae hatch and drop into the water where they seek out sponges to feed on. They use their elongated mouthparts to pierce the sponge and suck the fluids within. The larvae of some species cling to the surface of the sponge while others take refuge in the sponge's internal cavities. The fully grown larvae leave the water and spin a cocoon in which to pupate. Ross Piper|Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals , Greenwood Publishing Group .
Bioerosion
The Caribbean chicken-liver sponge Chondrilla nucula secretes toxins that kill coral polyp s, allowing the sponges to grow over the coral skeletons. Others, especially in the family Clionaidae , use corrosive substances secreted by their archeocytes to tunnel into rocks, corals and the shells of dead mollusc s. Sponges may remove up to convert|1|m|ft per year from reefs, creating visible notches just below low-tide level.
Diseases
Caribbean sponges of the genus Aplysina suffer from Aplysina red band syndrome . This causes Aplysina to develop one or more rust-colored bands, sometimes with adjacent bands of necrosis|necrotic tissue (dead). These lesions may completely encircle branches of the sponge. The disease appears to be Contagious disease|contagious (spread by physical contact). The rust-colored bands are caused by a cyanobacterium , but it is unknown whether this organism actually causes the disease.cite journal | author=Olson, J. B., Gochfeld, D. J., and Slattery, M. | title= Aplysina red band syndrome: a new threat to Caribbean sponges | journal=Diseases of aquatic organisms | month=July | year=2006 | volume=71 | issue=2| pages=163–8| pmid=16956064 | doi=10.3354/dao071163 News report at http://www.practicalfishkeeping.co.uk/pfk/pages/item.php? news=1113 New disease threatens sponges (Practical Fishkeeping)
Collaboration with other organisms
In addition to hosting photosynthesizing endosymbionts, sponges are noted for their wide range of collaborations with other organisms. The relatively large encrusting sponge Lissodendoryx colombiensis is most common on rocky surfaces, but has extended its range into seagrass meadows by letting itself be surrounded or overgrown by seagrass sponges, which are distasteful to the local starfish and therefore protect Lissodendoryx against them; in return the seagrass sponges get higher positions away from the sea-floor sediment.cite journal | author=Wulff, J. L | title=Collaboration among sponge species increases sponge diversity and abundance in a seagrass meadow | journal=Marine Ecology | volume=29 | year=2008 | pages=193–204 | doi=10.1111/j.1439-0485.2008.00224.x | issue=2
Shrimp s of the genus Synalpheus form colonies in sponges, and each shrimp species inhabits a different sponge species, making Synalpheus one of the most diverse crustacea n genera.cite journal | author=Duffy, J. E. | year=1996 | title=Species boundaries, specialization, and the radiation of sponge-dwelling alpheid shrimp | journal=Biological Journal of the Linnean Society | volume=58 | issue=3 | pages=307–324 | doi=10.1111/j.1095-8312.1996.tb01437.x | url= http://web.vims.edu/bio/mobee/Duffy96BJLS.pdf? svr=www | accessdate=2008-11-11
Evolutionary history
Fossil record
Annotated image | float=left | caption=Fossil sponge Raphidonema faringdonense from Cretaceous rocks in England | image=Fossil Sponge Raphidonema.jpg | width=150 | image-width=250 | height=150| image-left=-50 | image-top=-20 | annotations= Annotation|0|0|& nbsp;Annotated image |float=right | caption= Archaeocyathid structure | image=Archaeocyatha.png| width=150 | image-width=150 | height=235 | image-top=-5 | annotations= Annotation|4|11| 1 Annotation|9|60| 2 Annotation|17|87| 3 Annotation|27|124| 4 Annotation|141|14| 5 Annotation|139|64| 6 Annotation|117|124| 7 Annotation|2|175| 1 :& nbsp;Gap& nbsp; 2 :& nbsp;Central& nbsp;cavity& nbsp; 3 & nbsp;Internal wall& nbsp; 4 :& nbsp;Pore ( all walls have pores)& nbsp; 5 & nbsp;Septum& nbsp; 6 & nbsp;Outer wall& nbsp; 7 & nbsp;Holdfast24-isopropyl cholestane is a stable derivative of 24-isopropyl cholesterol , which is thought to be produced by demosponge s but not by eumetazoa ns ("true animals", i.e. cnidaria ns and bilateria ns). Since choanoflagellate s are thought to be animals' closest single-celled relatives, a team of scientists examined the biochemistry and gene s of one choanoflagellate species. They concluded that this species could not produce 24-isopropylcholesterol but that investigation of a wider range of choanoflagellates would be necessary in order to prove that the fossil 24-isopropylcholestane could only have been produced by demosponges.cite journal | author=Kodner, R. B., Summons, R. E., Pearson, A., King, N., and Knoll, A. H. | title= Sterols in a unicellular relative of the metazoans | month=July | year=2008 | volume=105 | pmid=18632573| issue=29 | pmc=2481317 | pages=9897–9902 | doi=10.1073/pnas.0803975105 | journal=Proceedings of the National Academy of Sciences
Although a previous publication reported traces of the chemical 24-isopropyl cholestane in ancient rocks dating to ma|1800cite journal | author=Nichols, S., and Wörheide, G. | title=Sponges: New Views of Old Animals | journal=Integrative and Comparative Biology | year=2005 | volume=45 | issue=2 | pages=333–334 | doi=10.1093/icb/45.2.333 | pmid=21676777 , 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 ma|635cite journal | author=Love, G.D., Grosjean, E., Stalvies, C., Fike, D.A., Grotzinger, J.P., Bradley, A.S., Kelly, A.E., Bhatia, M., Meredith, W., Snape, C.E., Bowring, S.A., Condon, D.J., and Summons, R.E. | title=Fossil steroids record the appearance of Demospongiae during the Cryogenian period | journal=Nature | year=2009 | volume=457 | pages=718–721 | doi=10.1038/nature07673 | pmid=19194449 | issue=7230 , 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, ~ma|713 in Oman)".
Although molecular clocks and biomarkers suggest sponges existed well before the Cambrian explosion, Silica spicule s like those of demosponges are absent from the fossil record until the Cambrian cite journal | author= Sperling, E.A., Robinson, J.M., Pisani, D., and Peterson K.J. | title=Where's the glass? Biomarkers, molecular clocks, and microRNAs suggest a 200-Myr missing Precambrian fossil record of siliceous sponge spicules | journal=Geobiology | year=2010 | volume=8 | pages=24–36 | doi=10.1111/j.1472-4669.2009.00225.x | pmid= 19929965 | issue= 1 , although one unsubstantiated report exists of spicules in rocks dated around ma|750Cite book | author=Reitner, J., and Wörheide, G. | contribution=Non-Lithistid Fossil Demospongiae – Origins of their Palaeobiodiversity and Highlights in History of Preservation | editor=Hooper, J. N. A., and Van Soest, R. W. M. | title=Systema Porifera: A Guide to the Classification of Sponges | publisher=Kluwer Academic Plenum | location=New York | year=2002 | url= http://webdoc.sub.gwdg.de/pub/geo/geobiologie/2005/reitner/2002-porifera.pdf |format=PDF| accessdate=2008-11-04, although this appears unlikely based on the above reference. Well-preserved fossil sponges from about ma|580 in the Ediacaran period have been found in the Doushantuo Formation . These fossils, which include spicule s, pinacocyte s, porocyte s, archeocyte s, sclerocyte s and the internal cavity, have been classified as demosponges. Fossils of glass sponge s have been found from around ma|540 in rocks in Australia, China and Mongolia.cite journal | doi=10.5194/bg-4-219-2007 | author=Müller, W. E. G., Li, J., Schröder, H. C., Qiao, L., and Wang, X. | title=The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a review | journal=Biogeosciences | volume=4 |pages=219–232 | year=2007 | issue=2 Early Cambrian sponges from Mexico belonging to the genus Kiwetinokia show evidence of fusion of several smaller spicules to form a single large spicule. McMenamin, M. A. S. 2008. Early Cambrian sponge spicules from the Cerro Clemente and Cerro Rajón, Sonora, México. Geologica Acta , v. 6, n. 4, p. 363-367. Calcium carbonate spicules of Calcarea|calcareous sponges have been found in Early Cambrian rocks from about ma|530|523 in Australia. Other probable demosponges have been found in the Early Cambrian Chengjiang fauna , from ma|525|520.cite journal | author=Li, C-W., Chen, J-Y., and Hua, T-E. | title=Precambrian Sponges with Cellular Structures | journal=Science | month=February | year=1998 | volume=279 | issue=5352 | pages=879–882 | doi=10.1126/science.279.5352.879 | pmid=9452391 Freshwater sponges appear to be much younger, as the earliest known fossils date from the Mid- Eocene period about ma|48|40. Although about 90% of modern sponges are demosponges , fossilized remains of this type are less common than those of other types because their skeletons are composed of relatively soft spongin that does not fossilize well.cite web | url = http://www.ucmp.berkeley.edu/porifera/demospongia.html | accessdate=2888-11-27 | title=Demospongia | publisher=University of California Museum of Paleontology
Archaeocyathid s, which some classify as a type of coralline sponge, are common in the Cambrian period from about ma|530, but apparently died out by the end of the Cambrian ma|490.
Family tree
clade
1=clade
1= Fungi
2=clade
1= Choanoflagellate s
label2= Metazoa
2=clade
1= Glass sponge s
2=clade
1= Demosponge s
2=clade
Calcareous sponges
label2= Eumetazoa & nbsp;& nbsp;
2=clade
Comb jellies
2=clade
1= Placozoa
2= Cnidaria (jellyfish, etc.)Simplified family tree showing Calcarea|calcareous sponges as closest to more complex animals
clade
1=clade
1= Plant s
2= Fungi
label3= Metazoa
3=clade
1=Most demosponge s
2=clade
Calcareous sponges
2=clade
1= Homoscleromorpha
label2= Eumetazoa
2=clade
1= Cnidaria (jellyfish, etc.)
2=Other metazoa nsSimplified family tree showing Homoscleromorpha as closest to more complex animals
In the 1990s sponges were widely regarded as a monophyletic group, in other words all of them descended from a common ancestor that was itself a sponge, and as the "sister-group" to all other metazoa ns (multi-celled animals), which themselves form a monophyletic group. On the other hand some 1990s analyses also revived the idea that animals' nearest evolutionary relatives are choanoflagellate s, single-celled organisms very similar to sponges' choanocytes – which would imply that most Metazoa evolved from very sponge-like ancestors and therefore that sponges may not be monophyletic, as the same sponge-like ancestors may have given rise both to modern sponges and to non-sponge members of Metazoa. cite journal | author=Borchiellini, C., Manuel, M., Alivon, E., Boury-Esnault, N., Vacelet J., and Le Parco, Y. | title=Sponge paraphyly and the origin of Metazoa | journal=Journal of Evolutionary Biology | volume=14| issue=1| pages=171–179 | year=2001 | doi=10.1046/j.1420-9101.2001.00244.x
Analyses since 2001 have concluded that Eumetazoa (more complex than sponges) are more closely related to particular groups of sponges than to the rest of the sponges. Such conclusions imply that sponges are not monophyletic, because the last common ancestor of all sponges would also be a direct ancestor of the Eumetazoa, which are not sponges. A study in 2001 based on comparisons of ribosome DNA concluded that the most fundamental division within sponges was between glass sponge s and the rest, and that Eumetazoa are more closely related to Calcarea|Calcareous sponges , those with calcium carbonate spicule s, than to other types of sponge. In 2007 one analysis based on comparisons of RNA and another based mainly on comparison of spicules concluded that demosponges and glass sponges are more closely related to each other than either is to calcareous sponges, which in turn are more closely related to Eumetazoa.cite journal | author=Medina, M., Collins, A. G., Silberman, J. D., and Sogin, M. L. | title=Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA | journal=Proceedings of the National Academy of Sciences | month=August | year=2001 | volume=98 | pmid=11504944 | issue=17 | pmc=55517 | pages=9707–9712 | doi=10.1073/pnas.171316998
Other anatomical and biochemical evidence links the Eumetazoa with Homoscleromorpha , a sub-group of demosponges. A comparison in 2007 of cell nucleus|nuclear DNA , excluding glass sponges and Ctenophora|comb jellies , concluded that: Homoscleromorpha are most closely related to Eumetazoa; calcareous sponges are the next closest; the other demosponges are evolutionary "aunts" of these groups; and the chancelloriidae|chancelloriids , bag-like animals whose fossils are found in Cambrian rocks, may be sponges.cite journal | author = Sperling, E.A. | coauthors = Pisani, D. and Peterson, K.J. | year = 2007 | title = Poriferan paraphyly and its implications for Precambrian paleobiology | journal=Journal of the Geological Society of London | volume=286 | pages = 355–368 | doi = 10.1144/SP286.25 | url = http://www.dartmouth.edu/~peterson/Sperling,%20Pisani%20and%20Peterson.pdf |format=PDF| accessdate = 2008-11-04 The sperm of Homoscleromorpha share with those of Eumetazoa features that those of other sponges lack. In both Homoscleromorpha and Eumetazoa layers of cells are bound together by attachment to a carpet-like basal membrane composed mainly of "type IV" collagen , a form of collagen not found in other sponges – although the spongin fibers that reinforce the mesohyl of all demosponges is similar to "type IV" collagen.cite journal | author=Exposito, J-Y., Cluzel, C., Garrone, R., and Lethias, C. | title=Evolution of collagens | journal=The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology = | volume=268 | issue=3 | pages=302–316 | doi=10.1002/ar.10162 | pmid=12382326 | year=2002
The analyses described above concluded that sponges are closest to the ancestors of all Metazoa, in other words of all multi-celled animals including both sponges and more complex groups. However, another comparison in 2008 of 150 genes in each of 21 genera, ranging from fungi to humans but including only two species of sponge, suggested that ctenophora|comb jellies ( ctenophora ) are the most basal lineage of the Metazoa included in the sample. If this is correct, either modern comb jellies developed their complex structures independently of other Metazoa, or sponges' ancestors were more complex and all known sponges are drastically simplified forms. The study recommended further analyses using a wider range of sponges and other simple Metazoa such as Placozoa .cite journal | author=Dunn, C. W., Hejnol, A., et al. | year=2008 | title=Broad phylogenomic sampling improves resolution of the animal tree of life | journal=Nature | volume = 452 | pages = 745–9 | doi=10.1038/nature06614 | pmid=18322464 | issue=7188 The results of such an analysis, published in 2009, suggest that a return to the previous view may be warranted. 'Family trees' constructed using a combination of all available data - morphological, developmental and molecular - concluded that the sponges are in fact a monophyletic group, and with the cnidarian s form the sister group to the bilaterians.cite doi|10.1371/journal.pbio.1000020
Archaeocyathid s are very common fossils in rocks from the Early Cambrian about ma|530|520 but are not found after the Late Cambrian. It has been suggested that they were produced by: sponges; cnidaria ns; algae ; foraminifera ns; a completely separate phylum of animals, Archaeocyatha; or even a completely separate Kingdom (biology)|kingdom of life, labelled Archaeata or Inferibionta. Since the 1990s archaeocyathids have been regarded as a distinctive group of sponges.cite journal | author=Rowland, S. M. | year=2001| title=Archaeocyatha: A history of phylogenetic interpretation | journal= Journal of Paleontology | volume=75 | pages=1065–1078 | url= http://findarticles.com/p/articles/mi_qa3790/is_200111/ai_n8958761/pg_1? tag=artBody;col1 | accessdate=2008-11-05 | doi=10.1666/0022-3360(2001)075<1065:AAHOPI>2.0.CO;2 | issn=0022-3360 | issue=6
Annotated image | float=left | caption= Halkieriid sclerite structure | image=Halkieriid sclerite structure 300.png | width=200 | height=96 | image-width=200 | image-left=0 | image-top=0| annotations = Annotation|141|44| = skinAnnotation|141|64| = aragonite Annotation|141|84| = fleshIt is difficult to fit chancelloriids into classifications of sponges or more complex animals. An analysis in 1996 concluded that they were closely related to sponges on the grounds that the detailed structure of chancellorid sclerites ("armor plates") is similar to that of fibers of spongin , a collagen protein , in modern keratose (horny) demosponge s such as Darwinella . cite journal | author=Butterfield, N. J., and C. J. Nicholas | year=1996 | title=Burgess Shale-type preservation of both non-mineralizing and "shelly" Cambrian organisms from the Mackenzie Mountains, northwestern Canada | journal=Journal of Paleontology | volume=70 | pages=893–899 | doi= | issue=6 However another analysis in 2002 concluded that chancelloriids are not sponges and may be intermediate between sponges and more complex animals, among other reasons because their skins were thicker and more tightly-connected than those of sponges. cite journal | author=Janussen, D., Steiner, M., and Zhu, M-Y. | title=New Well-preserved Scleritomes of Chancelloridae from the Early Cambrian Yuanshan Formation (Chengjiang, China) and the Middle Cambrian Wheeler Shale (Utah, USA) and paleobiological implications | journal=Journal of Paleontology | month=July | volume=76 |issue=4 | pages=596–606 | doi=10.1666/0022-3360(2002)076<0596:NWPSOC>2.0.CO;2 | url= http://jpaleontol.geoscienceworld.org/cgi/content/abstract/76/4/596 | accessdate=2008-08-04 | year=2002 | issn=0022-3360 Free full text without images at cite news | url= http://findarticles.com/p/articles/mi_qa3790/is_200207/ai_n9134583/pg_1? tag=artBody;col1 | title=(as above) | accessdate=2008-08-04 | work=Journal of Paleontology | first=Dorte | last=Janussen | year=2002 In 2008 a detailed analysis of chancelloriids' sclerites concluded that they were very similar to those of halkieriid s, mobile bilaterian animals that looked like slug s in chain mail and whose fossils are found in rocks from the very Early Cambrian to the Mid Cambrian. If this is correct, it would create a dilemma , as it is extremely unlikely that totally unrelated organisms could have developed such similar sclerites independently, but the huge difference in the structures of their bodies makes it hard to see how they could be closely related. cite journal | title=Skeletal microstructure indicates Chancelloriids and Halkieriids are closely related | author=Porter, S. M | journal=Palaeontology | volume=51 | issue=4 | year=2008 | pages=865–879 | doi=10.1111/j.1475-4983.2008.00792.x
Taxonomy
For a long time sponges were assigned to a separate subkingdom, Parazoa ("beside the animals"), separate from the Eumetazoa which formed the rest of the Kingdom (biology)|kingdom Animalia . They are now classified as a phylum within Animalia, and divided into Class (biology)|classes mainly according to the composition of their skeleton s:
Hexactinellida (glass sponges) have silicate spicule s, the largest of which have six rays and may be individual or fused. The main components of their bodies are syncytia in which large numbers of cell share a single external Cell membrane|membrane .
Calcarea have skeletons made of calcite , a form of calcium carbonate , which may form separate spicules or large masses. All the cells have a single nucleus and membrane.
Most Demospongiae have silicate spicules or spongin fibers or both within their soft tissues. However a few also have massive external skeletons made of aragonite , another form of calcium carbonate. All the cells have a single nucleus and membrane.
Archeocyatha are known only as fossils from the Cambrian period.
In the 1970s sponges with massive calcium carbonate skeletons were assigned to a separate class, Sclerospongiae , otherwise known as "coralline sponges".cite journal | author=Hartman, W. D., and Goreau, T. F. | year=1970 | title=Jamaican coralline sponges: Their morphology, ecology and fossil relatives | journal=Symposium of the Zoological Society of London | volume = 25| pages = 205–243 http://mgg.rsmas.miami.edu/groups/sil/work1.htm (cited by MGG.rsmas.miami.edu). However in the 1980s it was found that these were all members of either the Calcarea or the Demospongiae.Cite book | author=J. Vacelet | year=1985 | contribution=Coralline sponges and the evolution of the Porifera | pages=1–13 | editor=Conway Morris, S., George, J. D., Gibson, R., and Platt, H. M. | title=The Origins and Relationships of Lower Invertebrates | publisher= Oxford University Press | isbn=019857181
So far scientific publications have identified about 9,000 poriferan species, of which: about 400 are glass sponges; about 500 are calcareous species; and the rest are demosponges. However some types of habitat, such as vertical rock and cave walls and galleries in rock and coral boulders, have been investigated very little, even in shallow seas.
Use
By dolphins
A report in 1997 described use of sponges as a tool by bottlenose dolphins in Shark Bay in Western Australia. A dolphin will attach a marine sponge to its rostrum (anatomy)|rostrum , which is presumably then used to protect it when searching for food in the sandy sea floor|sea bottom .cite journal | author=Smolker, R. A., et al. | title=Sponge-carrying by Indian Ocean bottlenose dolphins: Possible tool-use by a delphinid | journal=Ethology | year=1997 | volume=103 | pages=454–465 | doi=10.1111/j.1439-0310.1997.tb00160.x | issue=6 The behaviour, known as sponging , has only been observed in this bay, and is almost exclusively shown by females. A study in 2005 concluded that mothers teach the behaviour to their daughters, and that all the sponge-users are closely related, suggesting that it is a fairly recent innovation.cite journal | author=Krutzen M, Mann J, Heithaus M.R., Connor R. C, Bejder L, Sherwin W.B. | title=Cultural transmission of tool use in bottlenose dolphins | journal= Proceedings of the National Academy of Sciences | volume=102 | issue=25 | year=2005 | pages=8939–8943 | doi=10.1073/pnas.0500232102 | pmid=15947077 | pmc=1157020. News report at http://news.nationalgeographic.com/news/2005/06/0607_050607_dolphin_tools.html Dolphin Moms Teach Daughters to Use Tools, publisher National Geographic ).
By humans
Main|Sea sponge aquaculture
Skeleton
Main|Sponge (material)The calcium carbonate or silica spicule s of most sponge genus|genera make them too rough for most uses, but two genera, Hippospongia and Spongia , have soft, entirely fibrous skeletons. Early Europeans used soft sponges for many purposes, including padding for helmets, portable drinking utensils and municipal water filters. Until the invention of synthetic sponges, they were used as cleaning tools, applicators for paints and ceramic glaze s and discreet contraceptive s. However by the mid-20th century, over-fishing brought both the animals and the industry close to extinction.cite book | author=McClenachan, L. | chapter=Social conflict, Over-fishing and Disease in the Florida Sponge Fishery, 1849-1939 | pages=25–27 | title=Oceans Past: Management Insights from the History of Marine Animal Populations | editor=Starkey, D. J. Holm, P., and Barnard, M. | publisher=Earthscan| year=2008 | isbn=1844075273 | url= http://books.google.com/? id=cGEeEfFegvEC& pg=PA26& dq=sponge+fishing | accessdate=2008-11-12
See also sponge diving .
Many objects with sponge-like textures are now made of substances not derived from poriferans. Synthetic sponges include personal and household sponge (tool)|cleaning tools , breast implant s,cite book | author=Jacobson, N. | title=Cleavage | publisher=Rutgers University Press | isbn=0813527155 | year=2000 | page=62 | url= http://books.google.com/? id=3ZIw_3Px4AEC& pg=PA62& dq=sponge+synthetic | accessdate=2008-11-12 and contraceptive sponge s.cite web |title=Sponges |work=Cervical Barrier Advancement Society |year=2004 |url= http://www.cervicalbarriers.org/information/sponges.cfm |accessdate=2006-09-17 Typical materials used are cellulose foam, polyurethane foam, and less frequently, silicone foam.
The luffa "sponge", also spelled loofah , which is commonly sold for use in the kitchen or the shower, is not derived from an animal but from the fibrous "skeleton" of a gourd ( Cucurbitaceae ).cite journal | author=Porterfield, W. M. | title=Loofah — The sponge gourd | journal=Economic Botany | volume=9| issue=3 | month=July | year=1955 | pages=211–223 | doi=10.1007/BF02859814
Antibiotic compounds
Sponges have medicine|medicinal potential due to the presence in sponges themselves or their microbial symbiosis|symbiont s of chemicals that may be used to control virus es, bacteria , tumor s and fungi. cite book| author=Imhoff, J. F., and Stöhr, R. | chapter=Sponge-Associated Bacteria | pages=43–44 | editor=Müller, W. E. G. | title=Sponges (Porifera): Porifera | publisher=Springer | year=2003 | isbn=354000968X cite journal| author=Teeyapant, R., Woerdenbag, H. J., Kreis, P., Hacker, J., Wray, V., Witte, L., and Proksch P. | title=Antibiotic and cytotoxic activity of brominated compounds from the marine sponge Verongia aerophoba | journal=Zeitschrift für Naturforschung C | volume=48 | pages=939–45 | year=1993
http://www.biology.ualberta.ca/courses.hp/zool250/animations/Porifera.swf Water flow and feeding in the phylum Porifera (sponges) - Adobe Flash|Flash animations of sponge body structures, water flow and feeding
http://www3.wooster.edu/geology/Bioerosion/Bioerosion.html Bioerosion website at The College of Wooster
http://www.spongepage.info/ Carsten's Spongepage, Information on the ecology and the biotechnological potential of sponges and their associated bacteria.
http://fcit.usf.edu/FLORIDA/lessons/tarpon/tarpon.htm History of Tarpon Springs, Florida sponge industry
