Abstract
The incorporation and retention of water-borne strontium in otoliths (asterisci and/or lapilli) were studied using the freshwater goldfish Carassius auratus. The effects of strontium concentrations, temperature, and 17β-estradiol were examined using atomic absorption spectrophotometry and X-ray analysis. Water-borne strontium (0.1, 1.0, and 10.0 mgl-1) was incorporated into otoliths (asterisci) in a concentration-dependent manner after an 88-day exposure, but a high concentration of 10.0 mgl-1 rather depressed the rate of incorporation. Similar results were seen with Sr-Ca ratios in plasma and otoliths. The strontium incorporatedinto otoliths remained after 92 days in nonstrontium-enriched water, while that in scales and ribs decreased. Otolith (lapillus) Sr-Ca ratios distinctly differ d between freshwater (Sr/Ca=2.6×10-3) -and diluted (1/9, 1/6, and 1/3) seawater (25×10-3 on an average)-reared groups, but no difference was found among the seawater groups. These ratios linearly increased with temperatures between 16 and 24°C in asterisci (r=0.65). However, they somewhat decreased at 28°C. A single administration of 17β-estradiol resulted in hypercalcemia and decreas d strontium incorporation into the lapillus but not in the asteriscus. The lapi lus contained 12 times more strontium than the asteriscus.
