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Acicula are the chitinous support rods within parapodia found in the class Polychaeta. ...[gastropod] Acicula is a genus of very small land snails with an operculum, terrestrial gastropod mollusks in the family Aciculidae. Species within the genus Acicula include: ...
• (n.) One of the needlelike or bristlelike spines or prickles of some animals and plants; also, a needlelike crystal.
A·cic'u·la noun ; plural Aciculæ [ Latin , a small needle, dimin. of acus needle.] (Nat. Hist.) One of the needlelike or bristlelike spines or prickles of some animals and plants; also, a needlelike crystal. 
[n] - a needle-like part or structure of a plant or animal or crystal
acicula (s), aciculae (pl) 1. A technical name for a slender needle-like body; such as, the spines or prickles with which some animals and plants are furnished, or the needle-like crystals of certain minerals. 2. An needle-shaped part, as of a plant or crystal.
noun a needlelike part or structure of a plant or animal or crystal; as a spine or bristle or crystal