was half that of the N1–OH toxin. Though the ability of the
toxin conversion in the crab was not directly investigated in
this experiment, there are some previous papers about the
conversion of the toxins. Chemical transformation by natural
reductant such as glutathione and cysteine (Asakawa et al.,
1987), and bacterial transformation in coral reef crab (Kotaki
et al., 1985), were reported in relation to the reductive
conversion of N1–OH toxin. Oshima (1995b) observed the
reductive conversion of the toxins in the extract of scallop, and
also suggested that such reductive processes commonly occur
when the toxins are transmitted through the food chain. The
difference in the toxin profile between the prey species and
crab is therefore most plausibly explained by such reductive
conversion.