The Collaborative International Dictionary of English v.0.48:

Clasper \Clasp"er\ (kl[.a]sp"[~e]r), n.
   1. One who, or that which, clasps, as a tendril. "The
      claspers of vines." --Derham.
      [1913 Webster]

   2. (Zool.)
      (a) One of a pair of organs used by the male for grasping
          the female among many of the Crustacea.
      (b) One of a pair of male copulatory organs, developed on
          the anterior side of the ventral fins of sharks and
          other elasmobranchs. See Illust. of Chim[ae]ra.
          [1913 Webster]