ABSTRACT
The reader will surely already have realized that the large areas of permeable epithelium in contact with the surrounding water imply that extra renal routes of excretion and ion exchange can be exploited, in contrast to the renal routes of most terrestrial forms, but before considering the mechanisms involved (recently reviewed by Evans et al., 2005), we may first examine the situation in hagfish, unique not only in being isosmotic with seawater, but also in having blood Na+ and Cl-levels similar to seawater.
