ABSORPTION AND EXCRETION OF COPPER ION DURING SETTLEMENT AND METAMORPHOSIS OF THE BARNACLE BALANUS AMPHITRITE NIVEUS

Abstract

1. Sites of copper ion concentration in barnacle cyprids from normal sea water both planktonic and settled, suggest that the barnacle absorbs copper from the medium through permeable surfaces and eliminates excess copper by excretion through the epithelia of the hind-gut. Reservoirs within which copper storage may occur have been identified. A metabolic role is suggested for copper in normal physiology of barnacle settling stages. 2. Copper deposits are consistently absent from both decorticated settlers and from two stages of the young adults. 3. Exposure of planktonic cyprids and early settled forms to a high-copper medium resulted in increased rate of elimination from the gut epithelium, and identified various surface areas of the thorax as absorption sites. Transport of copper ions in solution from absorption surfaces to points of excretion is probably by way of circulating body fluids. 4. Copper deposits were observed in decorticated settlers only during later phases of this stage and in areas previously identified as active points of exchange with ambient sea water. 5. Absorption of copper from sea water containing excess copper during the stages of shell formation occurs via single-cell extensions through the thickness of the forming shell. Elimination of copper through a lobe of the digestive caecum was also noted during this period. 6. Copper localization studies on post-decortication stages suggest that copper absorption is coincident with absorption of other ions, particularly calcium, which is highly concentrated during these developmental periods. 7. Copper absorption during the cyprid-form developmental stages occurs through respiratory surfaces. It is suggested that the anti-fouling effectiveness of copper is due to interference with normal respiratory exchange. 8. The effect of the copper-ion concentration in the ambient medium on oxygen uptake of cyprids is currently being investigated and will form the substance of a subsequent communication.