Yu-Chi Tung

Publications (2)3.06 Total impact

• Article: Effect of environmental calcium levels on calcium uptake in tilapia larvae Oreochromis mossambicus

  Pung-Pung Hwang, Yu-Chi Tung, Min-Hwang Chang
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  ABSTRACT: Effects of environmental calcium concentrations on the survival, growth, body calcium content and calcium uptake kinetics in developing tilapia (Oreochromis mossambicus) larvae were studied. Fertilized eggs were incubated in high- and low-calcium artificial freshwater (0.88–0.96 mmol l–1 vs. 0.02–0.03 mmol l–1 CaCl2 or CaSO4) until 3 days after hatching. Tilapia larvae showed similar hatching rates and wet weights in either high- or low-calcium medium, indicating neither the development nor the growth in tilapia larvae was affected by the environmental calcium levels. The body calcium content in low-calcium groups was about 90–95% that of high-calcium groups, No matter what calcium source was used (CaCl2 or CaSO4), acclimation to low calcium medium caused a stimulation of calcium uptake (measured in 0.2 mmol l–1 calcium),i.e., 1.2–1.3 fold higher than that of high calcium groups. This enhanced calcium uptake capacity was characterized by a 50% decrease in Km and a 25% increase in Jmax. Effect of different calcium salts on calcium influx was significant only in low calcium level,i.e., calcium influx in low-CaCl2 group higher than that in low-CaSO4 group. These results suggest that tilapia larvae are able to modulate their calcium uptake mechanism to maintain normal body calcium content and growth in environments with different levels of calcium.
  Fish Physiology and Biochemistry 01/1996; 15(5):363-370. · 1.53 Impact Factor
• Source

  Available from: ntur.lib.ntu.edu.tw

  Article: Calcium balance in embryos and larvae of the freshwater-adapted teleost, Oreochromis mossambicus

  Pung-Pung Hwang, Ya-Ni Tsai, Yu-Chi Tung
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  ABSTRACT: Changes in Ca2+ content and flux, and the development of skin chloride cells in embryos and larvae of tilapia, Oreochromis mossambicus, were studied. Tilapia embryos hatched within 96h at an ambient temperature of 26–28°C. Total body Ca2+ content was maintained at a constant level, about 4–8 nmol per individual, during embryonic development. However, a rapid increase in body Ca2+ level was observed after hatching, 12.8 to 575.3 nmol per individual from day 1 to day 10 after hatching. A significant influx and efflux of Ca2+ occurred during development, with the average influx rate for Ca2+ increasing from 5.9 pmol mg−1 h−1 at 48h postfertilization to 47.8 pmol mg−1 h−1 at 1 day posthatching. The skin was proposed as the main site for Ca2+ influx before the development of gills, and the increased Ca2+ influx may be ascribed to gradual differentiation of skin surface and chloride cells during embryonic development. Ca2+ efflux was 16–56 pmol mg−1 h−1 in 1-day-old larvae. The resulting net influx of Ca2+, 10–12 pmol mg−1 h−1, accounted for the increased Ca2+ content after hatching. When comparing the measured and estimated ratios of efflux and influx, active transport was suggested to be involved in the uptake of Ca2+. Chloride cells, which may be responsible for the active uptake of Ca2+, started to differentiate in the skin of embryos 48h after fertilization, and the density of chloride cells increased following the development. A possibility of active transport for Ca2+ in early developmental stages of tilapia is suggested.
  Fish Physiology and Biochemistry 04/1994; 13(4):325-333. · 1.53 Impact Factor