Effects of salinity on osmoregulation during the embryonic development of the bullseye puffer (Sphoeroides annulatusJenyns 1842)

Abstract

To evaluate the effect of salinity on the hatching rate, hatching time, survival percentage, osmoregulation pattern and the incidence of abnormalities in newly hatched larvae, embryos of Sphoeroides annulatus (Jenyns 1842) were exposed to 5, 12, 19, 26, 33, 35 and 40 psu. The hatching percentage (HP), survival percentage (PS), normal larvae (PN), deformed larvae (PD) and hatching time (HT) were significantly affected by salinity (P < 0.05). The embryos exposure to 5 psu caused that HP, PS, and PN had lower values (2.6 ± 0.32, 7.78 ± 0.88 and 70.37 ± 7.75% respectively), PD and HT had the highest values 26.67 ± 7.54% and 55.53 ± 0.59 h respectively. However, the survival of newly hatched larvae was not possible in 5 ups, though it was in 40 ups. Osmotic pressure (OP) remained constant in each salinity, whereas isosmotic points changed from 435.5 mOsm kg−1 in 21 h post fertilization to 342.8 mOsm kg−1 at 47 h post fertilization, obtaining a pattern of hyper-osmoregulation at lower salinities and hypo-osmoregulation in higher salinities. This study is the first carried out on embryos of this species; therefore, the obtained information is essential to improve strategies and growing conditions in their initial development.