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This article is about the skeletal structure. See also Spicule (solar physics)
Spicule (solar physics)

In solar physics, a spicule is a dynamic jet of about 500 km diameter on the Sun. It moves upwards at about 20 km/s from the photosphere. They were discovered in 1877 by Father Angelo Secchi of the Vatican Observatory in Rome....
 and Spicule (glass manufacture)
Spicule (glass manufacture)

Spicules are tiny glass flakes which are formed during the manufacture of glass vials. A glass tube is extruded at a constant rate and a jet of water applied to the hot glass is used to cut the blank tube to length....
.


Spicules are skeletal
Skeleton

In biology, a skeleton is a rigid framework that provides protection and structure in many types of animal, particularly those of the phylum Chordata and of the superphylum Ecdysozoa....
 structures that occur in most sponge
Sea sponge

The sponges or poriferans are animals of the phylum Porifera . Their bodies consist of an outer thin layer of cells, the pinacoderm and an inner mass of cells and skeletal elements, the choanoderm....
s. They provide structural support and deter predators.






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This article is about the skeletal structure. See also Spicule (solar physics)
Spicule (solar physics)

In solar physics, a spicule is a dynamic jet of about 500 km diameter on the Sun. It moves upwards at about 20 km/s from the photosphere. They were discovered in 1877 by Father Angelo Secchi of the Vatican Observatory in Rome....
 and Spicule (glass manufacture)
Spicule (glass manufacture)

Spicules are tiny glass flakes which are formed during the manufacture of glass vials. A glass tube is extruded at a constant rate and a jet of water applied to the hot glass is used to cut the blank tube to length....
.


Microscopicspiculesfrompachastrellidsponge
Spicules are skeletal
Skeleton

In biology, a skeleton is a rigid framework that provides protection and structure in many types of animal, particularly those of the phylum Chordata and of the superphylum Ecdysozoa....
 structures that occur in most sponge
Sea sponge

The sponges or poriferans are animals of the phylum Porifera . Their bodies consist of an outer thin layer of cells, the pinacoderm and an inner mass of cells and skeletal elements, the choanoderm....
s. They provide structural support and deter predators. Large spicules, visible to the naked eye are referred to as megascleres, while smaller, microscopic ones are termed microscleres. The term spicule can also refer to structures on other organisms, such as the copulatory spicules of certain nematodes. This article discusses sponge spicules.

Spicules have four major symmetry types: Monaxon (simple cylinders with pointed ends), triaxon, tetraxon, and polyaxon. Sponges can be calcareous
Calcium carbonate

Calcium carbonate is a chemical compound with the chemical formula CalciumCarbonOxygen3. It is a common substance found as Rock in all parts of the world, and is the main component of seashells, snails, and eggshells....
, siliceous
Biogenic silica

Biogenic silica is the equivalent to the terms opal, biogenic opal, and amorphous opaline silica. BSi is essential to many plants and animals....
, or composed of spongin
Spongin

Spongin is a type of collagen protein that forms the fibrous skeleton of most organisms among the Phylum Porifera, the sponges.Spongin does not make up spicules....
. The meshing of many spicules serves as the sponge’s skeleton
Skeleton

In biology, a skeleton is a rigid framework that provides protection and structure in many types of animal, particularly those of the phylum Chordata and of the superphylum Ecdysozoa....
. The composition, size, and shape of spicules is one of the largest determining factors in sponge taxonomy
Taxonomy

Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
.

Spicules are formed by sclerocyte
Sclerocyte

Sclerocytes are spicule secreting cells, found in sponges. They secrete calcareous or siliceous spicules which are found in the mesohyl layer of sponges....
s, which are derived from archaeocytes. The sclerocyte begins with an organic filament, and adds silica to it. Spicules are generally elongated at a rate of 1-10 µm per hour. Once the spicule reaches a certain length it protrudes from the sclerocyte cell
Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
 body, but remains within the cell’s membrane
Cell membrane

The cell membrane is the interface between the cellular machinery inside the cell and the fluid outside.It is a semipermeable lipid bilayer found in all cell ....
. On occasion, sclerocytes may begin a second spicule while the first is still in progress.

Research on the Euplectella aspergillum (Venus' Flower Basket)
Venus' Flower Basket

The Venus' Flower Basket, or Euplectella aspergillum, is the only Hexactenellida in the phylum Porifera to be used in hobbyists' aquariums....
 demonstrated that the spicules of certain deep-sea sponges have similar traits to Optical fibre. In addition to being able to trap and transport light, these spicules have a number of advantages over commercial fibre optic wire. They are stronger, resist stress easier, and form their own support elements. Also, the low-temperature formation of the spicules, as compared to the high temperature stretching process of commercial fibre optics, allows for the addition of impurities
Impurity

Impurities are substances inside a confined amount of liquid, gas, or solid, which differ from the chemical composition of the material or compound....
 which improve the refractive index
Refractive index

The refractive index of a medium is a measure for how much the speed of light is reduced inside the medium. For example, typical soda-lime glass has a refractive index of 1.5, which means that in glass, light travels at times the speed of light in a vacuum....
. In addition, these spicules have built-in lenses
Lens (optics)

A lens is an optics device with perfect or approximate axial symmetry which transmittance and refraction light, converging or diverging the beam....
 in the ends which gather and focus light in dark conditions. It has been theorized that this ability may function as a light source for symbiotic
Symbiosis

The term symbiosis commonly describes close and often long-term interactions between different biological species. The term was first used in 1879 by the Germany mycology Heinrich Anton de Bary, who defined it as "the living together of unlike organisms"....
 algae
Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds....
 (as with Rosella racovitzae) or as an attractor for shrimp
Shrimp

Shrimp are swimming, Decapoda crustaceans classified in the infraorder Caridea, found widely around the world in both fresh water and seawater. Adult shrimp are Filter feeder benthic animals living close to the bottom....
 which live inside the Venus' Flower Basket. However, a conclusive decision has not been reached; it may be that the light capabilities are simply a coincidental trait from a purely structural element.

In a 2008 study using light sensitive paper and Tethya aurantium, it was confirmed that spicules do funnel light deep inside sea sponges.