Inhabiting The Virtually Uninhabitable_By Amy Heels

With salt concentrations three times that of the ocean and a pH higher than baking soda, it is not surprising that Mono Lake, California is almost completely uninhabitable. Until recently it was thought that only diving flies and brine shrimp were tough enough to inhabit these waters (algae and bacteria aside), however researchers at the California Institute of Technology have found that microscopic worms are also braving the difficult conditions, eight species of them to be precise. 


One of these species, scientifically named Auanema sp., is of particular interest as not only are they extremely adaptable, as we will discuss shortly, they also have three different sexes - male, female and hermaphrodite. A hermaphrodite is an organism which can produce both male and female sex-cells (eggs and sperm, in humans) and is therefore capable of self-fertilisation. This is significant as microscopic worms such as these, scientifically known as nematodes, usually have just two sexes - male and hermaphrodite. The ability to reproduce either sexually or asexually is advantageous to the species as it allows diversity in favourable conditions but also the rapid, asexual reproduction of lots of offspring in unfavourable conditions. These offspring can then go find somewhere else to inhabit. The existence of three sexes is not the only anomaly about this species. They also carry their young inside of them like a kangaroo, where other nematodes lay eggs to be fertilised and develop externally of their ‘parent(s)’. 


So versatile is this species, that they can survive in concentrations of arsenic 500 times what the average human can endure as well as surviving in normal laboratory conditions for scientific study. These extreme powers of endurance aptly place the creature in the ‘extremophile’ category - an extremophile being a creature that thrives in environments in which most species cannot survive. The knowledge we can gain from these tiny creatures could also aid human survival. For a long time now, humans have been modelling crucial cellular processes in simpler ‘model organisms’ to discover more about our own biology. Model organisms range from E. coli to fruit flies (D. melanogaster) to pigs (S. scrofa) and have revealed lifesaving information in the fields of cancer research, heart disease, DNA regulation and so much more. 


Auanema sp. could be the next big model organism due to its ability to endure such high concentrations of arsenic. Arsenic is a toxic chemical in its inorganic form. According to the World Health Organisation (WHO), it poses a particular threat to human health as it can pollute water sources and crops, causing illness in anyone that consumes the affected food and water. This is particularly evident in countries such as Bangladesh, Argentina, Chile, China and the United States where arsenic is naturally present in groundwater at high concentrations. So much so that it has now been recognised that at least 140 million people in 50 countries are consuming water with arsenic concentrations above what the WHO considers to be safe. This tragically leads to 43,000 deaths per annum in Bangladesh alone. Arsenic intoxication can also cause cancer, skin lesion, diabetes, heart disease, lung disease and other debilitating conditions in the long term. 


Although study of Auanema sp. is in its infancy, if we can learn about the cellular processes this species uses to tolerate such high concentrations of arsenic, we could start to find a solution to arsenic intoxication in humans and save lives.


References 

Weston,P., (2019). New species of worm with three sexes discovered in highly salty Californian lake. Independent [online]. 26 September. 26 September 2019, 17:39. [Viewed 30 March 2020]. Available from: URL:  https://www.independent.co.uk/environment/nematodes-worms-three-sexes-california-mono-lake-sex-a9121526.html

Science Daily., (2019). Otherworldly worms with three sexes discovered in Mono Lake [online]. Science Daily. [Viewed 30 March 2020]. Available from: URL:

https://www.sciencedaily.com/releases/2019/09/190926141715.htm

Haag, E. S. et al., (2018). From “the Worm” to “the Worms” and Back Again: The Evolutionary Developmental Biology of Nematodes. Genetics [online]. 210(2). 397-433. [Viewed 30 March 2020}. Available from: doi: https://doi.org/10.1534/genetics.118.300243

World Health Organisation., (2018). Arsenic [online]. World Health Organisation. [Viewed 30 March 2020]. Available from: URL: https://www.who.int/news-room/fact-sheets/detail/arsenic

Flanagan, S. V. et al., (2012). Arsenic in tube well water in Bangladesh: health and economic impacts and implications for arsenic mitigation. Bulletin of the World Health Organisation [online]. 90(11). 839-846. [Viewed 30 March 2020]. Available from: doi: 10.2471/BLT.11.101253.

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