1) An acicula 
aciculum (s), acicula (pl) 1. A needle-like spine or bristle, as is present in certain types of worms or flagellates. 2. A projecting cluster of bristles or setae found in certain annelid worms or a fingerlike or handlike bristle seen in certain flagellate protozoa. 3. In zoology, one of the slender, sharp stylets embedded in the parapodia o...
an acicula. · one of the slender, sharp stylets embedded in the parapodia of certain annelid worms, as the polychaetes.