Sex-specific accumulation of Cd-metallothionein in the abdominal muscle of the coral prawn Metapenaeopsis crassissima from a natural population

Female coral prawns Metapenaeopsis crassissima from natural populations in Shark Bay, Western Australia contain high concentrations of Cd in both their midgut gland and abdominal muscle. The biochemical form of this Cd was examined by gel filtration chromatography, HPLC, MALDI mass spectrometry and N-terminal sequence analysis. The majority of the Cd was soluble (mean values: midgut 91%, muscle 57%; n = 4), and eluted (gel filtration) in a single 10 kDa-peak which could be further resolved into five peaks by reversed-phase HPLC. Mass spectral data on the peaks showed molecular masses of 5778, 5876 and 6008. N-terminal sequencing of two of the peaks gave typical decapod crustacean MT-sequences, one of which contained an N-terminal residue of methionine. The methionine variant of MT has previously only been reported in laboratory studies of Cd-stressed crustaceans. The presence of the methionine variant of MT in a natural population of crustaceans containing high Cd levels suggests its possible use as a biomarker of toxic response to Cd exposure