Trace metal contents in male, non-ovigerous and ovigerous females, and the egg sacs of the marine copepod, Euchaeta concinna Dana, 1849 (Copepoda, Euchaetidae), collected from the southern East China Sea

Marine copepods have a great ability to accumulate trace metals from seawater. The trace metal content in marine copepods may vary both intra- and inter-specifically. However, the known specific trace metal content of the copepod sexes and according to the ovigerous status of the females is very limited. Copepod samples of Euchaeta concinna Dana, 1849, were collected from the southern East China Sea and separated into four groups: males; non-ovigerous females; ovigerous females without egg sacs, and egg sacs, in order to analyse the trace metal contents (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in these samples. These trace metal contents were found to range between 0.04 and 195.7 μg/g. Zinc, Fe, and Cu were the major components among the trace metals studied and their concentrations generally exceeded 10 μg/g. The trace metal contents in the copepod body generally exceeded the amount in the egg sacs. However, the Cr concentration in the egg sacs was much higher than that in the copepod body, either male or female, and the value ranked as second just behind Zn among the metals studied. The nickel content was also slightly higher in the egg sacs. This study provides the important finding that E. concinna egg sacs contained Cr concentrations out of all proportions to that of the copepod body. Yet, why E. concinna egg sacs contain relatively higher Cr concentrations than the body remains a question to be answered.