John Wiley & Sons, Ltd.

Stage susceptibility of Japanese medaka (Oryzias latipes) to selenomethionine and hypersaline developmental toxicity

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Anthropogenic disturbance of seleniferous soils can lead to selenium contamination of waterways. Although selenium is an essential micronutrient, bioaccumulation and maternal transfer of proteinaceous selenomethionine (SeMet) can result in embryotoxicity. Furthermore, as the climate changes, the salinity of spawning grounds in water‐restrained estuaries is increasing. While a small increase in salinity may not directly impact adult fish, it may alter the detoxification strategies of developing organisms. Previous research indicates that hypersalinity may potentiate SeMet embryo toxicity at an early developmental stage. However, embryonic development is a complex, spatiotemporal process with a constantly shifting cellular microenvironment. In order to generate thresholds and an adverse outcome pathway for the interactions between selenium and salinity, we sought to identify windows of susceptibility for lethality and deformities in the Japanese medaka (Oryzias latipes). Embryos were treated in freshwater or saltwater for 24hours with 0.5µM, 5µM, and 50µM SeMet at 6 different developmental stages (9, 17, 25, 29, 34, and 38). Survival, hatch, deformities (total, type and severity), and day to hatch were quantified. Se embryo tissue measurements were performed. SeMet exposures of 5µM and 50µM significantly decreased survival and hatch at all stages. However, SeMet uptake was stage dependent and increased with stage. Stage 17 (early neurulation) was identified as the most susceptible stage for lethality and deformities. SeMet in saltwater caused significantly greater toxicty than freshwater at stage 25 (early organogenesis), suggesting a role for liver and osmoregulatory organogenesis in toxicity. This article is protected by copyright. All rights reserved

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