spicule

zoology

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July 14, 2026

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In zoology, a spicule is a small, pointed, and typically hard body. Sponges, which are unusual animals lacking definite organs, use spicules as part of their skeleton. These skeletons can be mineral-based, made of calcium carbonate or silicic acid, or composed of protein like spongin.12

Spicules are classified by their function and form. Megascleres provide support, while microscleres offer protection and aid in support. They come in various shapes, such as needle-like, star-shaped, or anchor-shaped, and are crucial for taxonomic identification within sponge species. Some cnidarians, like soft corals, also incorporate spicules into their structures to stiffen the colony.13

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mollusk
External features
…minute, spinelike, hard bodies (spicules), or both (aplacophoran level). The chitons (class Polyplacophora) develop a series of eight articulating plates or valves often surrounded by a girdle of cuticle with spicules; in all other mollusks, the mantle secretes an initially homogeneous shell. The mantle and shell are laterally compressed…
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…minute, spinelike, hard bodies (spicules), or both (aplacophoran level). The chitons (class Polyplacophora) develop a series of eight articulating plates or valves often surrounded by a girdle of cuticle with spicules; in all other mollusks, the mantle secretes an initially homogeneous shell. The mantle and shell are laterally compressed…
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cnidarian
Support mechanisms and skeletons
…horny protein gorgonin with calcareous spicules fused to form a solid or jointed central rod. Soft coral spicules are discrete, mostly microscopic objects of diverse shapes that vary from needle-like to club- and anchor-shaped. Located in the ectoderm, spicules stiffen the colony. In some species the several spicules that form…
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…horny protein gorgonin with calcareous spicules fused to form a solid or jointed central rod. Soft coral spicules are discrete, mostly microscopic objects of diverse shapes that vary from needle-like to club- and anchor-shaped. Located in the ectoderm, spicules stiffen the colony. In some species the several spicules that form…
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