Fig. 5. Relationship between liver enzyme activities of betaine synthesis (nmol min^–1 mg protein^–1) and the accumulation of betaine in the muscle (µmol g^–1) of marine, euryhaline and freshwater elasmobranchs. Figures are for muscle betaine and (A) liver choline dehydrogenase activity (ChoDH), (B) liver betaine aldehyde dehydrogenase (BADH), (C) ratio of BADH/ChoDH. The regression equations for A and B are only for species able to survive in full-strength seawater (marine and euryhaline) while the equation in C is for all species; for C, the equation (not shown) for those species able to survive under marine conditions is not significantly different from the regression equation including all species. Data are taken from Table 1 and Fig. 3.