In Situ Monitoring of Genotoxic Pollution in Laguna de Bay Using Micronucleus Assay in Tilapia (Oreochromis niloticus) Peripheral Erythrocytes

Abstract

Laguna de Bay, an indispensable source of fish for human consumption and domestic water for Metropolitan Manila in the next years, experiences degradation due to the increasing urbanization and industrialization around its terrestrial watershed. In the present study, the genotoxicity of the lake was investigated using micronucleus (MN) assay in peripheral blood of Oreochromis nilolicus. Other nuclear abnormalities (NA), namely blebbed, notched, and lobed, were also evaluated. There was no significant difference in the frequencies of micronuclei among the four study sites and negative control. Moreover, positive linear correlation between the frequencies of MN and other NA was observed. This demonstrated the usefulness of scoring NAs as complementary index of chromosomal damage. Also, in terms of the frequencies of other nuclear abnormalities, notched nuclei were significantly higher in East Bay, while lobed nuclei were significantly higher in the Central Bay. This study highlights that tilapia exhibit various physiological responses, such as the reported resistance to heavy metals and multixenobiotic resistance, that conceal the effects of genotoxic pollutants when evaluated using micronucleus assay. Furthermore, the induction of micronuclei may be affected by both biotic factors, like developmental stage, sex, and feeding habits, and abiotic factors like environmental temperature. Thus, monitoring the biological impacts of potential genotoxic pollutants in Laguna de Bay is a complex process and many possible interactive factors needs to be further examined.