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Sponge spicules are made of calcium carbonate or silica. Large spicules visible to the naked eye are referred to as megascleres or macroscleres, while smaller, microscopic ones are termed microscleres. The composition, size, and shape of spicules are major characters in sponge systematics and taxonomy.
The calcareous sponges [2] [3] (class Calcarea) are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate, in the form of high-magnesium calcite or aragonite. While the spicules in most species are triradiate (with three points in a single plane), some species may possess two ...
These sponges are massive or encrusting in form and have a very simple structure with very little variation in spicule form (all spicules tend to be very small). Reproduction is viviparous and the larva is an oval form known as an amphiblastula. This form is usual in calcareous sponges but is less common in other sponges.
Bolosoma stalked glass sponge. Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges.They are usually classified along with other sponges in the phylum Porifera, but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma.
The calcium carbonate or silica spicules of most sponge genera make them too rough for most uses, but two genera, Hippospongia and Spongia, have soft, entirely fibrous skeletons. [13]: 88 Early Europeans used soft sponges for many purposes, including padding for helmets, portable drinking utensils and municipal water filters.
Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. [6] Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous diatoms. [7] The many diverse orders in this class include all of
The spicules are composed of three perpendicular rays, giving them six points. Spicules are microscopic, pin-like structures within the sponge's tissues that provide structural support for the sponge. It is the combination of spicule forms within a sponge's tissues that helps identify the species.
The siliceous sponges form a major group of the phylum Porifera, consisting of classes Demospongiae and Hexactinellida. They are characterized by spicules made out of silicon dioxide, unlike calcareous sponges. Individual siliachoates (silica skeleton scaffolding) can be arranged tightly within the sponginocyte or crosshatched and fused together.