dracunculi

from The Collaborative International Dictionary of English v.0.48

Dracunculus \Dra*cun"cu*lus\, n.; pl. {Dracunculi}. [L., dim. of
   draco dragon.] (Zool.)
   (a) A fish; the dragonet.
   (b) The Guinea worm ({Filaria medinensis}).
       [1913 Webster]