The term ‘‘chloride cell’’ relates to the function
of the MRC in Cl elimination. In seawater
teleosts, the MRCs have quite convincingly been
shown to be sites of active Cl elimination and
hence the name is fitting (Marshall, 2002, this
issue). In the agnathans, elasmobranchs, and
freshwater teleosts, the evidence that MRCs are
involved in Cl fluxes is indirect or lacking all
together. So in order to avoid any confusion on the
matter, we will only use the term ‘‘chloride cell’’
when referring to the seawater teleost MRC unless
otherwise noted. However, in general, numerous
mitochondria in these cells are thought to supply
the ATP for ion-transport proteins to drive the
vectorial transport of ions as part of ion and acid–
base regulation (see Claiborne, 2002; Marshall,
2002)