Branchial

from WordNet (r) 3.0 (2006)

branchial
    adj 1: of or relating to gills (or to parts of the body derived
           from embryonic gills)

from The Collaborative International Dictionary of English v.0.48

Branchial \Bran"chi*al\, a. (Anat.)
   Of or pertaining to branchi[ae] or gills.
   [1913 Webster]

   {Branchial arches}, the bony or cartilaginous arches which
      support the gills on each side of the throat of fishes and
      amphibians. See Illustration in Appendix.

   {Branchial clefts}, the openings between the branchial arches
      through which water passes.
      [1913 Webster]