Frogs have unique ability to see color in the dark – Herp Digest

Science Daily, 2/28/17- Lund University, Sweeden

The night vision of frogs and toads appears to be superior to that of all other animals. They have the ability to see colour even when it is so dark that humans are not able to see anything at all. This has been shown in a new study by researchers from Lund University in Sweden.

Most vertebrates, including humans, have two types of visual cells located in the retina, namely cones and rods. The cones enable us to see colour, but they usually require a lot of light and therefore stop working when it gets dark, in which case the rods take over so that we can at least find our way home, albeit in black and white.

In toads and frogs the rods are a bit special, however. It was previously known that toads and frogs are unique in having rods with two different sensitivities. This has not been found in other vertebrates, and it is also the reason why researchers have long suspected that frogs and toads might be able to see colour also in low-light conditions. The new study was first in proving this to be true, and the results exceeded all expectations.

"It's amazing that these animals can actually see colour in extreme darkness, down to the absolute threshold of the visual system. These results were unexpected," says Professor of Sensory Biology Almut Kelber at the Faculty of Science, Lund University.

It was during the third of three experiments that the researchers discovered that frogs are able to use their rods to distinguish colour in extreme darkness. The researchers studied the frogs in a situation that is as serious as it is common, namely, when frogs need to find their way out in case they are trapped in conditions of complete darkness. This is potentially an everyday occurrence, taking place in dark dens and passageways on the ground. In such instances, finding the exit becomes crucial, which also means that the frog is inclined to make use of any sensory information that is available.

In the other experiments the researchers studied to what extent frogs and toads use their colour vision when searching for a mate or hunting for food. The results showed that the animals stop using their colour information fairly early when it comes to finding someone with whom to mate, whereas they continue to take advantage of their colour vision to select food in such low-light conditions that humans lose their ability to see colour.

"We have previously shown moths and geckos are also able to see colour in inferior light conditions compared to humans. However, frogs apparently have a unique ability to see colour in the dark," says Almut Kelber.

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Journal Reference:

            1          Carola A. M. Yovanovich, Sanna M. Koskela, Noora Nevala, Sergei L. Kondrashev, Almut Kelber, Kristian Donner. The dual rod system of amphibians supports colour discrimination at the absolute visual threshold. Philosophical Transactions of the Royal Society B: Biological Sciences, 2017; 372 (1717): 20160066 DOI: 10.1098/rstb.2016.0066

Throughout history, humans have preferred their pigs to be black, suggests study

New mutation found that suggests humans across the world have selected and bred black pigs
 

Date: September 6, 2016

Source: University of Oxford

New research suggests the Polynesians, Europeans and the Chinese have had a penchant for black pigs because of the novelty of their colour. Pigs have played an important cultural role in Hawaii since Polynesian explorers first brought them to Hawaii 800 years ago. Scientists led by Professor Greger Larson from Oxford examined the DNA sequences of modern feral Hawaiian pigs and discovered that a novel mutation is responsible for their black coats, a significant finding because the pigs were expected to have either the Asian or the European genetic mutation leading to their black colour. The study in the Royal Society journal, Open Science, says wild pigs would naturally have camouflaged coats. However, human societies have independently selected domesticated pigs that express the trait of black-coloured coats on at least three separate occasions.

Debate has centred on whether Hawaii's modern feral pigs (modern populations that were once descended from domestic pigs but are now living in the wild) are from Polynesian stock or whether they descend primarily from the European domestic pigs that travelled with explorer Captain Cook who arrived in Hawaii in 1778.

Scientists find that today's feral pigs ARE mainly the descendants of the Pacific family brought by the Polynesians. In addition, the scientists identified a new genetic mutation responsible for the black colouring of their coats. An international team of researchers studied the mitochondrial DNA and MC1R gene sequences in tissue samples collected from 57 modern feral Hawaiian pigs. They found a novel mutation in all the black-coloured pigs which is different to the mutation in European and Asian domestic pigs with black coats. This finding suggests that for thousands of years, humans in different parts of the world have been independently selecting and breeding pigs for their black colour.

Senior author Professor Greger Larson, from the Palaeogenomics and Bio-Archaeology Research Network at the University of Oxford, said: 'The first pigs introduced to Hawaii by the Polynesians were kept as domestic animals. No wild boar have black colours since natural selection only allows camouflaged pigs to survive long enough to reproduce. Humans, on the other hand, love all kinds of coloured coats and have selected for black coats at least three times independently in domestic pigs in Europe, Asia, and the Pacific. In the case of pigs, black has always been the new black.'

Continued  

Yellow or black, large or small? Ant color and body size respond strongly to environment

Date: September 8, 2016

Source: University of Liverpool

A University of Liverpool study of ants across three continents has revealed that their colour and size is strongly influenced by their environment, and that the dominant colour and average body size can change from year to year as temperatures vary. This finding has implications for how ant communities will cope with rising global temperatures.

Ants are ectotherms and so rely on the temperature of their surrounding environment to control their metabolic activity. Previous studies from individual locations or single species have found that larger bodied ectotherms with dark colouration do well in cold places. Large bodies retain heat whilst dark colours help individuals to gain heat quicker than their paler counterparts do. Combined, these two traits are highly beneficial as they allow ectothermic individuals to forage and remain active for longer even under cool conditions.

Researchers at the University's School of Environmental Sciences wanted to test whether these ideas of ectotherm thermoregulation held across species and at large geographic scales. They collected and analysed information on the abundance, body size and colour of ants on 14 different mountains from locations in South Africa, South America and Australia. Some of the sites were sampled repeatedly for up to seven years. This diversity of elevations and latitudes provided a huge range of external ambient temperatures (from 0.5 to 35°C).

They found that the colder the external temperature is, the larger and darker ants were, and vice versa. Consequently, communities of ants in sites closer to the South Pole or near the tops of mountains, where it was colder, would tend to be dominated by dark and large bodied ants. In warmer places the ant species were smaller and lighter in colour.

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