#morphologicalanalysis

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The Eye of Sauron in the Amazon

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It is not always easy to agree on a name for new species, but researchers at the Natural History Museum in London had no doubts when they encountered new species of vegetarian piranhas.

But let’s take a step back. In the past, defining an animal as belonging to a new species often relied on morphological characteristics. This is the case with the genus Myloplus, particularly the species Myloplus schomburgkii. Under this name, fish were grouped together that could be easily recognised by their vertical black bar in the centre of the body and their diet mainly consisting of plants and some insects, despite their close relationship to piranhas. Through a new and careful morphological analysis of multiple specimens combined with DNA barcoding, researchers realised that within the species Myloplus schomburgkii, there were actually two other species, all with a dark vertical bar on the side, but genetically distinct!

The two new species were named M. aylan and M. sauron. The specific name M. aylan honours the late Aylan Moraes Andrade, the son of Carine Moraes and Marcelo Andrade, one of the authors, who passed away prematurely. The specific name M. sauron alludes to the Eye of Sauron from J. R. R. Tolkien’s “The Lord of the Rings” as its body is marked with a vertical black bar tapering towards both ends, resembling the famous vertical-pupilled eye from the novel. Additionally, some specimens also have orange spots on their bodies, just like the Eye!

How did the researchers realise they were dealing with multiple species? They found significant molecular distances between the three lineages, well beyond the minimum threshold for fish species DNA barcoding (2%-3%). Myloplus schomburgkii differs from M. aylan and M. sauron by 7.9% and 9.7% respectively. The distance between M. aylan and M. sauron was even greater, at 11%.

The differences between the three species are not limited to genetics. To a keen eye, the same dark vertical bar can be easily used to distinguish the three species. Myloplus schomburgkii has a uniformly wide vertical dark bar compared to the two new species. In M. sauron, the vertical black bar tapers towards the ends forming tapered distal points, while in M. aylan, the vertical dark bar has a broader region near the lateral line and the ends do not taper.

The naming of the new species M. aylan and M. sauron reflects the deep connection between science and society, where every name tells a story. This discovery, made possible through a combination of morphological and genetic analyses, reminds us that our understanding of the natural world is continuously evolving. Nature always surprises us, and the identification of these new species highlights how vast and still partly unknown the animal kingdom is. The researchers invite us to maintain a watchful and curious eye, just like the Eye of Sauron, to continue exploring and discovering the wonders of nature.

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