Hemocyanin re-uptake in the renal and branchial heart appendages of the coleoid cephalopod Sepia officinalis

The renal and branchial heart appendages of Sepia officinalis L. were inves tigated in order to elucidate a possible involvement of their excretory epi thelia in hemocyanin metabolism. Immunocytochemical findings and tracer exp eriments indicate that after passing the barrier of ultrafiltration the hem ocyanin molecules are taken up by the epithelial cells of the renal and bra nchial heart appendages and are subsequently carried back to the circulator y system, suggesting a mechanism of hemocyanin recycling. Apart from a func tion in maintaining constant hemocyanin levels, the present study indicates that the renal and branchial heart appendages are also sites of temporary hemocyanin storage.