Effect Of Metal Ions On The Nacre Color And Metallothionein Expression In Pinctada Martensii

Pinctada martensii (P. martensii.) is distributed mainly in Japan, India, Indonesia andsouthern coast of China, is the major shell fish produced small and medium size of seapearls. At present, P. martensii was one of the main economic breeding shellfishes inGuangdong, Guangxi and Hainan. In this research, we mainly focus on the effect of themetal ions on the nacre color and the expression of metallothionein after adding somespecific ions in the feeding and breeding water. Results showed:1. Difference of metal ion content among different color shell in P. martensii.The individuals with distinct shell color was selected from black, red, white andgolden shell color cultured populations in P. martensii, the soft part was removed and theshells were washed, dried and grinded into sample, at last analyzed by ICP-MS. In the14tested elements, there were significant differences in the content of Mn, Zn, Cu, Cd indifferent color shell. Mn content in yellow shell is higher than white shell (P <0.05); Cucontent in black is higher than white (P <0.05), Cd is higher than other three shell colorindividuals; Zn content in red is higher than other three shell color individuals.2. Acute toxicology experiment of Cu, Zn, Mn, Cd in P. martensii.The results indicated that the96h median lethal concentration (96h LC50) of Cu2+,Zn2+, Cd2+, Mn2+were0.16mg/L,4.42mg/L,5.3mg/L and244mg/L, respectively, andthe safe concentration were0.016mg/L,0.442mg/L,0.53mg/L and24.4mg/L, respectively.The toxicity intensity of four metal ions were followed by Cu2+> Zn2+> Cd2+> Mn2+.3. Accumulation of four metals in Chlorella was studied.Results showed that balance time of accumulation for Cu2+, Zn2+, Cd2+, Mn2+were:2h,2h,4h and2h, respectively. The adsorption rates were87%,85%,56%and79%,respectively. The adsorption coefficient were1391,1000,245and686respectively.4. Influence on the nacre color after metal ions enrichment in P. martensiiUnder controlled conditions, enrichment experiments were carried in two ways for30days, one was fed with the chlorella which have accumulated the four metal ions(I-Cu、I-Zn、I-Mn and I-Cd), another was added the metal ions to breeding environmentdirectly(II-Cu、II-Zn、II-Mn and II-Cd). The ion content determination of in nacreous layershowed that: the metal ion content in experiment groups were higher than the controlgroup, but no significant difference (P>0.05).The outer edge of the nacre was measured by colorimeter after the experiment, recorded the color parameters and calculated the colordifference. Results showed that: there were significant differences in the tristimulus valuesand color parameters among the groups. Most of the color difference values were above1.5except I-Mn-Black, II-Cu-Black and II-Cu-I-Mn.5. The unigene of metallothionein (MT) from our previous research abouttranscriptome was265bp, encoding a polypeptide of85amino acids. In nonlethalconcentration, the expression changes of MT induced by Cu, Zn, Mn and Cd was detected.Result showed that the expression of MT increased after Cu treatment and achieved to themaximum at10days, then decreased gradually and recovered at20days. Similar resultswere got after Zn treatment, but the recovery process was relatively slowly. After Mntreatment, the expression of MT increased significantly at15days and decreased at20days.After Cd treatment, there was no significant change of the expression of MT.