Scales tell tales of toxic wetlands
Western Tiger Snake in its native wetland habitat. Image: Damian Lettoof
Scientists from Curtin University have used an NCRIS-enabled analytical technique, normally applied to rocks, in a different way; determining the concentration of metals accumulating in the scales of snakes living in urban wetland environments. The results are concerning, but the non-lethal approach to tissue sampling will prove advantageous for future studies.
Catching media eyes
Snake scales, like human fingernails and hair, accumulate toxins. This has led PhD candidate Damian Lettoof (School of Molecular and Life Sciences) and researchers at the AuScope GeoHistory Facility in the John de Laeter Centre at Curtin University, Western Australia (Kai Rankenburg, Bradley McDonald and (Noreen Evans), to add snake wrangling to their scientific tool kit.
Their novel research has already attracted the attention of editors at The Conversation, resulting in a case of snakes climbing the media ladder! With this in mind, we instead turn our attention in this story to the AuScope enabled laboratory method and snake wrangling aspects of this important story.
Scales and lasers
Traditionally, when investigating environmental contaminants, the livers of wetland species have been used as the test organ for contaminant exposure, but while the liver reflects a life history of exposure, the animal has to be sacrificed which is not ideal.
The breakthrough came when researchers recognised that many metals and metalloids (we will refer to them here both as ‘metals’ for brevity) bind to keratin, and that keratinous snake scales can be analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP MS). Discovering previous studies led by Hopkins (2013) and Burger (2017) were key to the team’s developments. Research collaborator, Prof. Noreen Evans who leads the AuScope GeoHistory Facility, reflects:
“We are always looking for new and exciting research opportunities that broaden the ways we can use our analytical infrastructure.
This was a really exciting application with results that could impact the way we monitor our wetland health, while preserving the life of test individuals. It's a win-win!”
Catching snakes
Sample sites across the Perth wetlands area (left) and research collaborator, Damian Lettoof and a Western Tiger snake, about to donate a sliver of scale, Perth wetlands (right). Image: Damian Lettoof
The first step is catching the snake and sampling the scales. Lead researcher, Damian Lettoof explains:
“It’s pretty easy but it's a two-person job. We catch the snake, one person safely restrains the head and the other cuts a belly scale with scissors. The same way one would cut a finger nail!”
Once gathered, the snake scales are returned to the lab. Each scale must be washed, dried and placed on double sided tape so that they can be expertly zapped using LA-ICP MS. The wetland snake scale’s metal load is compared to levels in captive tiger snake scales. A significantly higher concentration of metals in the wild snakes indicates environmental exposure. It became clear that titanium, vanadium, strontium, cesium thallium, thorium and uranium had been accumulating to levels of concern in the wild tiger snakes.
In this Perth wetland study, the metals in the snake scales were also compared with previous liver analyses. Results indicated comparable peaks in manganese, arsenic, selenium and antimony, which confirmed the viability of scales as an alternative and more ethical test to infer internal and environmental contamination levels.
A breakthrough for the wetlands
The AuScope enabled LA-ICP MS laboratory method is providing researchers with a significant increase in the speed of screening wetlands species. This technique is also testing a larger suite of metals than could be analysed using slower, more traditional digestion methods. An exciting development for all wetland species and the health of their wetlands with only minor discomfort for the local snakes. Using snakes as bioindicators of wetland contamination in this way is especially important given in our global context where:
“Up to 40% of the world’s species live and breed in wetlands, although now more than 25% of all wetlands plants and animals are at risk of extinction.” — UN Climate Change News, 01 October 2018
STORY IN A NUTSHELL
Researchers at Curtin University have successfully applied an NCRIS enabled geo-analytical technique to measure metal concentrations in snake scales to better understand urban wetlands contamination, catching the attention of The Conversation because of its future application.
AUTHORS
Prof. Noreen Evans,
Philomena Manifold
and Jo Condon