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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.
Spicules cover the thin dermal membrane, although the texture of the sponge itself is soft. The spicules are made of silica and provide structural support as well as protection. Freshwater sponge spicules come in many sizes and forms, including microscleres, emmula microscleres, and parenchyma macroscleres.
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 ...
Spongilla have a leuconoid body form with a skeleton composed of siliceous spicules. They are sessile organisms, attaching themselves to hard substrate like rocks, logs and sometimes to ground. [ 3 ] Using their ostia and osculum these sponges filter the water for various small aquatic organisms such as protozoans , bacteria , and other free ...
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.
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.