Tag Archives: nature

The redder the male, the more successful it is.


According to Joseph Corbo, an associate professor of pathology and immunology at Washington University, the genes affecting red coloration belong to a wider family of genes involved in detoxification. Redness may be a sign of a robust, quality mate who can easily cleanse harmful substances from his body.

“In many bird species, the redder the male, the more successful it is at finding mates,” – Joseph Corbo.

For more see http://www.deccanchronicle.com/science/science/200516/researchers-solve-mystery-of-red-colour-in-birds.html

Structural colours


Most colours around result from light being absorbed (electronic transitions) and scattered by dyes and/or pigments. However, there was an interesting article in The Guardian today about structural colour. Structural colour is quite common in nature; it occurs when light is scattered because of a regularity in packing or structure; the wavelength of the light that is most strongly scattered is determined by the repeat distance of this packing, which has to be comparable to the wavelength of the light.

eyes change colour?


I didn’t realise how sophisticated reindeers are. It turns out they have two layers of fur to help them keep warm, are able to shrink the pads on their hooves to give then better grip, and can detect ultraviolet light which enables them too see in very dim light. And it also turns out that their eyes can change colour in winter so that their vision is more sensitive. Reindeers, like cats, have a reflective layer behind the retina (which is the inside of the eye ball where all the light-sensitive cells are) that helps them to see in dim light. This is why, if you see a cat at night, you might see the eyes shining; you are seeing light being reflected back at you from the cat’s tapetum lucidum (which is the technical term for the layer behind the retina). The light that shines back in most animals with this layer is golden but in reindeer it apparently shifts to blue in the winter. The shift to blue allows more light to be scattered and improves the vision of the animal.

The full paper can be read in the Proceedings of the Royal Society.

special females

Our colour vision results from the fact that our eyes contain three types of light-sensitive cells or cones that have different wavelength sensitivity. Some people (called anomalous trichromats) are colour blind and this is usually because one of their cones is mutated and has a different wavelength sensitivity compared with those in so-called normal observers. Colour-blind is a misnomer really because anomalous trichromats can still see colour; they just have less ability to discriminate between colours than normals. Some people are missing one of the cone classes altogether and are referred to as dichromats; they have even poorer colour discrimination but can still see colour. Only monochromats are really colour blind and they are extremely rare.

For a long time I have known that some females have four cones classes (this makes them tetrachromats). Dr Gabriele Jordan, a researcher at the Institute of Neuroscience (Newcastle University) has spent the last 20 years working on human colour vision. She has discovered that tetrachromatic females exist and that although this gives them the potential for colour discrimination much better than normal trichromats in practice most have normal colour discrimination. However, in a recent report she has found a tetrachromat who really does have enhanced colour discrimination. This is really exciting news!

The report in the Daily Mail suggest that a functional tetrachromat could be able to see 99 million more hues than the average person. Personally I am skeptical of this claim even if, as I suspect, it means 99 million more hues than the average person. The number of colours that an average person can see is debatable but I think may be about 10 million (see my previous blog post).

natural colours

The Guardian has reported that Nestlé has removed artificial ingredients from their entire confectionary range. However, I am not sure that this is worth making too much of a song and dance about. The public have a natural aversion to artificial colorants. Surely natural is better? Well, not necessarily.

The foliage and berries of the Deadly Nightshade plant are extremely toxic. Apple seeds can be fatal if eaten in large enough quantities (they contain a small amount of amygdalin). The kidney bean is poisonous if not correctly cooked. The puffafish – known in Japan as Fugu – can be lethally poisonous due to its tetrodotoxin; therefore, it must be carefully prepared to remove toxic parts and to avoid contaminating the meat. All of these things are natural.

Lots of natural products are not harmful. But there are many many artificial chemicals that are completely identical (chemically) to their naturally occurring and harmless equivalents. It’s strange that we are so keen to believe that natural is good and man-made is bad. Sometimes it is true, but sometimes it is not.

good to be colour blind

Colour blindness is mainly a male affliction. Something like 8% of all men in the world are colour blind though, as I have mentioned before, this doesn’t mean that they cannot see colour but, rather, means that their colour discrimination is not as good as that of so-called normal observers (the rest of us, in common vernacular). See my earlier post. So we normally think of colour blindness as being something undesirable, something that ideally we would like to be able to cure.

Interesting then that new research at Anglia Ruskin University has suggested that colour blindness may even be an advantage. The study was led by Dr Andrew Smith and showed that colour-blind monkeys (tamarins, to be exact) were better than their ‘normal’ counter-parts at catching camouflaged insects (such as crickets). I guess what this means is that the camouflage is designed (I guess I should say, has evolved) to be effective when viewed by normal tamarins. So the colour-blind tamarins may be better off in some sense.

Dr Smith is also quoted as saying that there is some evidence that, in humans, dichromats (who have two classes of cone rather than three) may see better in dim light than trichromats. For further information see http://www.businessweekly.co.uk/academia-a-research/13403-colour-blind-monkeys-have-advantage-in-catching-camouflaged-prey.

colourful ants

Not sure what to say about this but I really like this picture. A scientist in India has experimented with ants whose transparent abdomens show the colour they have eating. He noticed they went white after drinking milk and then gave them sugar solutions coloured with different dyes. Apparently fond that ants preferred yellow and green solutions – perhaps these are better associated with sweetness. For the full story and some more great pictures see http://www.dailymail.co.uk/news/article-2022765/The-ants-multi-coloured-abdomens-exactly-theyve-eating.html

colour preferences

Many studies have been carried out over the last century or so on colour preferences. These generally reveal some quite remarkable consistencies. For example, although there are individual differences, on average people tend to like cooler colours (blues and greens) more so than warmer colours. I have been conducting my own – just for fun – survey on these pages (see http://colourware.wordpress.com/2011/02/22/favourite-colour-poll/) for the last few months: I asked people which colour they would prefer out of green, brown, yellow, orange, black, red, pink, purple, white, grey, blue and other. So far 45% of respondents have selected blue or green.

Whether gender or cultural affect colour preferences is more controversial although many studies have indicated that they may. The most significant work I know of in this regard is that published in Current Biology (2007) by a team lead by Anya Hurlbert of Newcastle University that adds substantial weight to the idea that there are statistically significant differences in colour preferences between males and females. Hurlbert’s team found that females prefer redder blues (tending towards pinks and red) than males. It is also suggested that the gender differences result from biological rather than cultural factors. Perhaps evolution favoured females who were better able to discriminate between ripe and unripe fruit or who could better discriminate between colours of faces.

If you are interested in this you may like to take part in a new global colour survey being carried out by one of my PhD students. You can see the survey here – https://www.keysurvey.co.uk/survey/365495/1a02/