Haemolymph magnesium levels in some oceanic crustacea

1. 1. Data are presented for the haemolymph magnesium levels of a number of amphipod and decapod species from oceanic mid-waters of the northern South Atlantic. 2. 2. The values are compared with neritic brachyuran haemolymph magnesium levels. 3. 3. No obvious correlation was apparent between the presumed general activity levels of the oceanic Crustacea and their haemolymph magnesium concentrations; non migrating forms had not dissimilar concentrations to those species known to undertake substantial daily vertical migration.