The effects of heavy metals on embryonic development of fish (a review)

Abstract

Early developmental stages of fish are particularly sensitive to water pollution. Heavy metals may affect various developmental processes during the embryonic period, which results in a reduction of offspring quantity and quality. Waterborne metals may accumulate in the gonads of spawners and adversely affect gamete production and viability, or exert direct toxic influence upon developing embryos. The egg shell does not fully protect the embryo against metal penetration, particularly during the swelling phase; thus, metals may accumulate in the egg. The results depend on metal concentration and range from developmental disturbances to death of the embryo. Metals disturb various processes of fish embryonic development and affect the development rate. Early stages just after fertilization are particularly sensitive to metal intoxication, when most disturbances and the highest embryonic mortality occur. Waterborne metals also promote developmental anomalies during organogenesis, including body malformations. Heavy metals often induce a delay in the hatching process, premature hatching, deformations and death of newly hatched larvae. All these disturbances result in reduced numbers and poor quality of the larvae, which show small body size, high frequency of malformations and reduced viability.

Detection of heavy metals bio-accumulation in scombrids for the determination of possible health hazard

“…One possible explanation to these findings is that an increase in the water temperature during summer increases heavy metals uptake in the fishes as compared to the winter season. Ahmed et al, (2013) supported this claim by stating that seasonal variations with regards to the concentration of heavy metals bio-accumulated in fish species follow a trend whereby the highest levels of heavy metals are accumulated during summer while the lowest values are accumulated during winter due to a rise in temperature which favours the uptake of certain heavy metals.The higher water temperature during the summer season as opposed to the lower temperatures during winter, favours a rise in the accumulation uptake and binding of metals probably due to higher metabolic rate in the fishes as proposed by Jezierska et al, (2009). Obasohan & Eguavoen (2008) also suggested that the rate of pollutant accumulation is favoured during high temperatures as the blood's oxygen affinity is decreased.…”

“…Fishes caught in winter and summer may therefore come from different marine environments and be subjected to different conditions. Jezierska et al (2009) suggested that accumulation is dependent on metal concentration, exposure time, route of metal uptake and environmental conditions such as water temperature, pH, salinity and feeding habits. The fishes caught during both seasons may belong to different schools of fish, come from different marine environments and have distinctive conditions proposed by Jezierska et al,(2009) which would explain the differences in accumulation patterns.…”

Effects of water pH on gamete activation, embryonic development, and larval normality in Prochilodus lineatus

“…Larval normality was analyzed under a stereomicroscope (10×) by evaluating 200 larvae from each experimental unit. Normal larvae were considered as those that showed no morphological alterations in the backbone, yolk sac, or head (FRAYSSE et al, 2006;JEZIERSKA et al, 2009). …”

Aquatic toxicity of manufactured nanomaterials: challenges and recommendations for future toxicity testing

“…It is well known that aquatic organisms are particularly sensitive to free metals, [27] and exposure at sub-lethal concentrations can affect several processes, including development, [28] movement, [29,30] hatch rate [31][32][33] and ion balance. [34] A major concern associated with metal-based NMs is the dissolution and release of ionic species in aquatic matrices.…”