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The meshing of many spicules serves as the sponge's skeleton and thus it provides structural support and potentially defense against predators. [1] 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.
Printable version; In other projects Wikidata item; ... Exopinococytes produce spicules which is a needle like process that serves as structure for the organism. [1]
While the spicules in most species are triradiate (with three points in a single plane), some species may possess two- or four-pointed spicules. [4] [5] Unlike other sponges, calcareans lack microscleres, tiny spicules which reinforce the flesh. In addition, their spicules develop from the outside-in, mineralizing within a hollow organic sheath ...
Cellular differentiation is an essential function of the archaeocyte. All specialized cells within the sponge have its origins with the archaeocyte. This is especially important in reproduction as the sex cells of the sponge in sexual reproduction are formed from these amoeboid cells.
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.
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. Siliceous spicules come in two sizes called megascleres and microscleres.
In A. meniscum, spicules are 6–7 mm (0.24–0.28 in), though in A. patina, they are only 1 mm (0.039 in). [8] The youngest spicules are found at the upper surface, particularly close to the rim, and are fairly easily distinguished. About 1–2 mm (0.039–0.079 in) from the base, they begin to recrystalise and are cemented together.