Bioaccumulation and Biodistribution of Selenium in Metamorphosing Tadpoles

Abstract

Selenium is an important macronutrient with a very narrow margin between essentiality and toxicity. Amphibians are hypothesized to be particularly sensitive due to the potential for metamorphosis-driven mobilization, which could transfer or concentrate contaminant burdens within specific organs. We explored the potential role of tissue degeneration and remodeling during anuran metamorphosis as a mechanism for altering tissue-specific Se burdens. Limnodynastes peronii tadpoles were exposed to dissolved Se (as selenite) for 7 days and depurated until completion of metamorphosis. Bioaccumulation and retention kinetics were assessed in whole tadpoles and excised tissues using gamma spectroscopy, and temporal changes in biodistribution were assessed using autoradiography. Tadpoles retained Se throughout metamorphosis, and partitioned the element predominantly within digestive and excretory tissues, including livers> mesonephros > guts > gallbladder. Importantly, our results demonstrate that Se biodistribution varies significantly throughout development. This is indicative of tissue transference, and particularly in tissues developing de novo after depuration. To the best of our knowledge, this is the first study demonstrating Se transference during metamorphic tissue remodelling. Further research is warranted to explore the fate and metabolism of Se (and other metal and metalloids) during anuran development and the implications of transference for influencing toxicity.

Ecotoxicological effects of decommissioning offshore petroleum infrastructure: A systematic review

“…Performing laboratory studies by exposing a variety of marine species to infrastructure-associated NORM contaminants will create refined estimates of contaminant bioavailability, radiation dose and subsequent assessments of effects from NORM and IR, combined with metals. Radiotracing techniques can provide new perspectives on the pathways and rates of uptake (e.g., bioaccumulation) and biomagnification processes of radioactive and non-radioactive contaminants (Cresswell et al, 2020;Lanctôt et al, 2017). Laboratory studies are needed to investigate the radiation-induced effects from NORM contaminants associated with petroleum scale.…”

Exploring New Frontiers in Marine Radioisotope Tracing – Adapting to New Opportunities and Challenges

“…Radiotracers have also been used to study how significant physiological changes, such as metamorphosis in amphibians, can affect contaminant bioaccumulation. Lanctôt et al (2017) used radiotracers of selenium ( 75 Se) to study the role of tissue degeneration and remodeling during anuran metamorphosis as a mechanism for examining tissue-specific contaminant burdens. The study with the Australian striped marsh frog, Limnodynastes peronii, demonstrated that selenium biodistribution (i.e., organ distribution) varies significantly throughout metamorphosis (Figure 3).…”

“…Digital autoradiographic false color phosphor images show Se distribution in ventral sections of tadpoles at developmental stage 33, 42, and 46 (Gosner, 1960), sampled after 3, 19, and 27 of depuration in clean water, respectively. Reprinted (adapted) with permission from Lanctôt et al (2017). Copyright (2017) American Chemical Society.…”

Synchrotron-Based Imaging Reveals the Fate of Selenium in Striped Marsh Frog Tadpoles

“…6,7 Analysis of contaminant biodistribution is critical to elucidate mechanisms of uptake, accumulation, and toxicity, yet few studies have examined Se distribution at the tissue and cellular levels in amphibians. 8,9 Recent work identified the eyes, digestive system, and excretory organs of tadpoles as important sites of Se accumulation and reported significant differences in bioaccu-mulation when exposed to different dissolved Se oxyanions. 9,10 It is well known that Se bioavailability is influenced by its chemical speciation in most aquatic species, though little is currently known on how exposure species influence the fate of Se in vivo.…”