[image] It has been suggested that Porifera/Temp be merged into this article or section. (Discuss)
? Sponges | ||||
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| Calcarea Hexactinellida Demospongiae Sclerospongiae |
The sponges or poriferans (from Latin porus "pore" and ferre "to bear") are animals of the phylum Porifera. They are primitive, Sessile, mostly marine, waterdwelling filter feeders that pump water through their matrix to filter out particulates of food matter. Sponges are among the simplest of animals, with partially differentiated tissues but without muscles, nerves, or internal organs. In some ways they are closer to being Cell colonies than multicellular organisms. There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the intertidal zone to as deep as 8,500 m (29,000 feet) or further. Though the Fossil record of sponges dates back to the Precambrian era, new species are still commonly discovered.
The structure of a sponge is simple: it is shaped like a tube, with one end stuck to a rock or other object and an open end, the Osculum, open to the environment. The Spongocoel, or interior of the sponge, is composed of walls perforated with microscopic pores that allow water to flow through the spongocoel.
Sponges have only three body types: asconoid, syconoid, and leuconoid. Asconoid and syconoid are both vase-like, while leuconoid take a lumpy shape much like a rock.
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Although they are animals, sponges may also be considered multi-cellular colonies. A sponge can be placed in a blender and any remaining living cells will reform themselves into another sponge. If multiple sponges are blended together, each species will recombine independently (contrast animal chimera such as the Geep).
It is thought that the earliest multicellular life on Earth was a sponge-like creature. The earliest known multicelled animal fossils are sponges from China that are roughly 600,000,000 years old. Sponges have not been as extensively studied as some other phyla and there may be some surprises still to be found. For example, it has recently been shown that some sponges are not sessile and can move to more favorable locations as rapidly as few centimeters a day. Another sponge, the Venus Flower Basket, has some newly discovered uses involving fiber optics.
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Adult sponges live in an attached position, and tend to lack any means of locomotion. The greatest numbers of sponges are usually to be found where a firm means of fastening is provided, such as on a rocky bottom. Some kinds of sponges are able to attach themselves to soft sediment by means of a root-like base. Sponges also live in quiet clear waters, because if the sediment is agitated by wave action or by currents, it tends to block the pores of the animal.
In common usage, the term sponge is usually applied to the skeletons of these creatures alone, from which the animal matter has been removed by maceration and washing. The material of which these sponges are composed is spongin. Calcareous and siliceous sponges are too harsh for similar use. Commercial sponges are derived from various species and come in many grades, from fine soft "lamb's wool" sponges to the coarse grades used for washing cars. The loofah or Luffa sponge, commonly sold for use in the kitchen or the shower, is not related to any animal sponge but is derived instead from a vegetable. Marine sponges come from fisheries in the Mediterranean and West Indies. The manufacture of Rubber, Plastic and Cellulose based synthetic sponges has significantly reduced the commercial sponge Fishing industry over recent years.
The fossil record of sponges is not abundant, except in a few scattered localities. Some Fossil sponges have worldwide distribution, while others are restricted to certain areas. Sponge fossils such as Hydnoceras and Prismodictya are found in the Devonian rocks of New York state. In Europe the Jurassic Limestone of the Swabian Alps are composed largely of sponge remains, some of which are well preserved. Many sponges are found in the Cretaceous Lower Greensand and Chalk Formations of England, and in rocks from the upper part of the Cretaceous period in France. A famous locality for fossil sponges is the Cretaceous Farringdon Sponge Gravels in Farringdon, Oxfordshire in England.
Fossil sponges vary in size from 1 cm (0.4 inches) to more than 1 metre (3.3 feet). They vary greatly in shape, being commonly vase-shapes (such as Ventriculites), spherical (such as Porosphaera), pear-shaped (such as Siphonia), leaf-shaped (such as Elasmostoma), branching (such as Doryderma), irregular or encrusting.
Detailed identification of many fossil sponges relies on the study of thin sections.