Negative properties of iodine and iodine metabolites can offset
potential benefits. For example, high iodine concentrations lead to
the formation of IO3and, through that, to a chemical reduction of
free oxygen that can be cytotoxic when released (Burgi et al.,
2001; Colin et al., 2003; Palmer et al., 2005). Some iodocarbons
can be toxic. So, perhaps larvae may have preferred unicellular algae with specific iodocarbons that were easier to detoxify, or algae
with lower iodine concentrations. In any case, the uptake of certain
iodocarbons might simply be a ‘safer’ way to attain iodine from
food, since bound iodine may be less reactive than in its free form.
This mechanism of iodine acquisition may be applicable to other
marine invertebrates that accumulate iodine but do not have thyroid follicles, or homologous structures to concentrate it