Abstract:
A teratogenic assay using cane toad (Bufo marinus) embryos was performed to assess the water quality of Laguna Lake. Standard Frog Embryo Teratogenesis Assay- Xenopus (FETAX) methods were adopted. Fertilized cane toad eggs were exposed to Laguna Lake water from three different sites: Northwest Bay, Central Bay and East Bay. Navotas River water was used as positive control and standard FETAX solution as negative control. Exposure groups were maintained using 96h static renewal system in which the exposure media were changed at 24h intervals. As endpoints, developmental parameters (mortality, malformation and hatching success) in the developing embryos were recorded during the 96h exposure. Results showed that there was a significant difference in the mean percentage malformation and mortality among the sites from Laguna Lake and the positive control. Northwest Bay yielded the highest percentage mortality and malformation; followed by Central Bay; and then East Bay. Only East Bay did not show a significant difference in the mean percentage malformation and mortality as compared to the negative control. The observed embryotoxic responses by cane toad embryos exposed to Laguna Lake water samples were discussed in relation to the analyzed contaminants in the lake. Overall, the present study concluded that Laguna Lake is still classified as Class C water; and it induces teratogenic effects to early life stages of cane toad embryos although not as teratogenic compared to Navotas River water.
