Six weeks after cautery of the external endolymphatic duct orifice of elasmobranchs, histologic distention of the endolymphatic sac itself was produced. However, there was no demonstrable behavioral correlate in sharks or rays of associated vestibular dysfunction either immediately or up to six weeks postoperatively (documented by movies, including underwater).
The unique anatomy of the endolymphatic system open to sea water via the external endolymphatic duct in elasmobranchs and ability to produce histologic evidence of hydrops indicate that this model system can be useful in study of inner ear fluid dynamics and of pathophysiology of hydrops. Paradoxically, this study strengthens conclusions made by Portmann in the 1920s about the importance of the endolymphatic sac and duct in inner ear fluid dynamics in elasmobranchs, even though we were unable to duplicate the behavioral effect.
I. Kaufman Arenberg, Nicholas L. Schenck, George S. Holtzscher, Richard M. Torack. Cauterization of the External Endolymphatic Duct in ElasmobranchsThe Portmann Experiment Revisited. Arch Otolaryngol. 1972;96(4):350–357. doi:10.1001/archotol.1972.00770090526010