Nav: Home

Pink or brown?

February 25, 2019

They're neither white and gold or black and blue. But in an optical puzzle akin to The Dress, colourful snails are causing scientists at the University of Nottingham to turn to technology to definitively decide whether some snails' shells are pink or brown.

The beautifully-hued Cepaea nemoralis - commonly known as grove snails - are found all over Europe in a range of colours, from yellow to pink to brown, with some also having 'humbug' style banding patterns.

But new research published in the academic journal Heredity, shows that differences in the way that the humans see and categorise colour, often makes it tricky to be sure about the colour of snail shells, leading to heated debate among scientists.

The problem of how to classify the colours has important implications for the study of the evolution of snails shell colour in response to factors including warming climate and hiding from predators.

Dr Angus Davison, Associate Professor and Reader in Evolutionary Genetics in the University's School of Life Sciences, who led the study, said: "The shell patterns and colour are hugely variable - almost like a snail fingerprint. As scientists, to ensure the accuracy of our studies and the subsequent interpretation, it is important that we have a reproducible measure of colour."

"The problem is that there are obvious differences in how humans perceive and categorise their colour, making it very difficult to compare the different types".

Over the past century, the study of animal colour has been critical in helping us to understand the principles of biology, particularly in relation to genetics and evolution. Studies on the distribution and the impact of colour on how predators may identify their prey have shaped our understanding of how natural and sexual selection operate in wild populations and the impact of climate change.

These snails - which are the second most common large snail in UK, and often found in gardens and hedgerows - have also been used in an "Evolution Megalab" experiment in which citizen scientists collect the snails and record the colour. Scientists compare the colour over time - there is a clear indication that the proportions of the different shell types are changing. But these citizen scientists face the same problem in classifying the colours.

Previous studies on grove snails have revealed that they can be sorted into roughly three colour groups - yellow, brown and pink.

It might be sensible to assume that yellow snails are found in dry, arid grasses where they can effectively blend into the background while their brown counterparts may stick to darker woodland environments to camouflage them. The snails uses their colour to evade predators - i.e. as camouflage - and to avoid overheating in open environments.

But surveys of the snails have shown that it's not always that simple - different coloured snails are found across a range of environments.

The colour may also have a role in how predators, particularly birds like song thrushes, choose their prey. Birds develop a preference for the commonest colour of snail over time, and so the rarer types escape predation.

To enable scientists to study the nuances of these issues accurately, they need a way of accurately sorting them into colour groups.

In the Nottingham study, grove snails from Britain and mainland Europe were categorised by Dr. Davison and PhD student Hannah Jackson, by eye.

The same snails were then analysed using a spectrometer, a machine that aims light at the snails, and measures the spectrum of light reflected from the shells.

Using these methods, the scientists were able to cluster the snails into brown, pink and yellow groups and this was compared to how the scientists had categorised the same snails by the naked eye.

The results showed that humans were largely capable of accurately categorising yellow snails but were less successful in identifying which snails were brown or pink. They also disagreed amongst themselves which were pink and which were brown.

The work provides scientists with a baseline measure for further studies into animal colour and the genes which underpin these variations.
-end-


University of Nottingham

Related Evolution Articles:

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.
Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.
A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.
Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?
Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.
Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.
Evolution of aesthetic dentistry
One of the main goals of dental treatment is to mimic teeth and design smiles in the most natural and aesthetic manner, based on the individual and specific needs of the patient.
An evolution in the understanding of evolution
In an open-source research paper, a UVA Engineering professor and her former Ph.D. student share a new, more accurate method for modeling evolutionary change.
Chemical evolution -- One-pot wonder
Before life, there was RNA: Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich show how the four different letters of this genetic alphabet could be created from simple precursor molecules on early Earth -- under the same environmental conditions.
Catching evolution in the act
Researchers have produced some of the first evidence that shows that artificial selection and natural selection act on the same genes, a hypothesis predicted by Charles Darwin in 1859.
More Evolution News and Evolution Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.