マガキ軟体部および貝殻内液への重金属の分配

抄録

A number of oysters were collected at the intertidal zone and kept in ice boxes, from which the specimens were serially picked up over 17 times at the interval of 6 hours for 96 hours. Copper, Zn Fe, Mn and Cd contents in soft bodies and shell cavity fluids were determined. At the same time, nitrogen contents in shell cavity fluids were also determined.
Regression and correlation coefficients between the metal and nitrogen contents and the serial times were not significant. Namely, the contents fluctuated independently without regard to the elapsed time. This proved that the preserving method was adequate to confine the metabolic activity of the specimen oysters.
Of the total absolute amounts of Cu and Zn in soft bodies and shell cavity fluids, more than 94% distributed in soft bodies, and consequently, less than 1% of the two metals existed in the fluids. Cadmium more than 98%, Mn more than 97% and Fe more than 96% distributed in soft bodies.
Although the levels of metal contents in shell cavity fluid were clearly less than those in soft bodies, the levels in the fluids were surprisingly higher than those in normal sea waters.
Taking into account the fluctuations of the heavy metal and the nitrogen contents in the shell cavity fluids mentioned above: it was suggested that the pre-concentration in shell cavity fluid through the uptake process of heavy metals is the main factor for the high heavy metal contents in the fluids.
Since, for specimens frozen deeply with shell valves, heavy metal contents in shell cavity fluid have been determined for a long time together with those in soft bodies, heavy metal contents of lamellibranchs are estimated somewhat higher than those obtained from fresh specimens.