Modulation of calcium balance in tilapia larvae (Oreochromis mossambicus) acclimated to low-calcium environments

This studs, examined how developing fish larvae regulate their Ca2+ balance for acclimation to low ambient Ca2+. Calcium balance in newly hatched larvae was examined individually. Developing not increased Ca2+ influx but also decreased Ca2+ efflux when they were acclimated to low-Ca2+ environments. After acclimation for 8 days, the influx and efflux of the low-Ca2+ - (0.02 mM) group were about 106% and 43%. respectively, compared to those of the high-Ca2+ (1.0 mM) group. Sensitivity and response to low-Ca2+ environments Lire a e-dependent. Upon acute exposure to low Ca2+, newly hatched (H0) larvae increased both Ca2+ influx (from 24% to 67% of high-Ca2+) and net uptake (from 5% to 69%) within 64 h. while 3-day-posthatching (H3) larvae managed to reach the levels of the control within 38 h. Declining Ca2+ efflux in H, larvae occurred 14 h after exposure, Much faster than those in H0 larvae (38 h). It is suggested that modulation of Ca2+-balance mechanisms in developing larvae is dependent upon the levels of Ca2+ in the larval body.