SELENIUM OCCURRENCE, DISTRIBUTION AND SPECIATION IN THE COCKLE ANADARA-TRAPEZIA AND THE MULLET MUGIL-CEPHALUS

Data on the factors affecting the accumulation of selenium in the cock le Anadara trapezia and mullet Mugil cephalus are presented, together with the distribution and speciation of selenium in tissues, Selenium concentration in whole cockles showed a small but significant decrease with weight, No further decrease in selenium concentration was appare nt once an organism reached 0.25 g dry weight, Selenium concentration in cockles was not dependent on sex, The tissue distribution of seleni um concentration in cockles was in the order gill > intestine > adduct or > mantle > foot. Selenium concentrations in liver tissues of mullet increased with the whole weight of the fish, In contrast, selenium co ncentrations in muscle, stomach, heart and kidney tissues were fairly low and constant in fish weighing less than 200 g (20 cm in length), F ish of greater weight and size (> 250 g and > 30 cm) had higher and mo re variable selenium concentrations, No differences in selenium concen tration between male and female fish occurred; however, the sex of man y of the fish could not be distinguished, The tissue distribution of s elenium concentration in mullet was in the order liver > stomach > hea rt > muscle > kidney. Most of the selenium recovered from both the coc kle tissues and the mullet muscle tissues was found to be associated w ith proteins and to be present as selenocysteine, A conceptual model i s presented for selenium transformations in marine organisms based on the formation of selenoamino-acids and subsequent incorporation into p roteins. (C) 1997 by John Wiley & Sons, Ltd.