Developmental pliability in zebrafish: An experimental enquiry of acute salinity stress on the early life of zebrafish

Abstract

This experiment was conducted to know the effects of salinity stress on the early life stages of zebrafish (Danio rerio). The objectives were evaluated by varying all combinations of developmental stages of zebrafish embryos exposing to a salinity gradient. The results demonstrated that zebrafish embryos (2 to 4-cell stage) could survive to hatching at 2 ppt (hatching rate 54.5%) but lowered at 4 ppt (hatching rate 23.5%). Acute exposure to 2 to 4-cell stage embryos for 60 and 120 min to different salinities (i.e., 0, 6, 8, 10, and 12 ppt) and then returned to freshwater (0 ppt) could hatch up to 8 ppt only at 60 min but not at 120 min exposures to embryos. The hatching rate was 14.5% and it took 20 h more times to hatch compared to control (0 ppt). While blastula stage exposed to 8 and 10 ppt salinities for 60 min, the hatching success was 59% and 36%, respectively. Although gastrula stage embryos were able to develop at 12 ppt salinity kept for 60 min the hatching success was markedly reduced (20.5%). Tolerance to salinity increased from advancing stages of development, i.e. the gastrulae were more tolerant of salinity change than the blastulae and the blastulae were more tolerant than the cleaving embryos. It is concluded that with the increasing salinities, the chances of embryogenesis and the survival of eggs decreased. In addition, tolerance to salinity increased from advanced stages of development. Keywords: Early development, Salinity, Stress, Zebrafish