Sharks see world as 50 shades of grey

Sharks are colour blind, a new molecular study by Australian scientists has confirmed, filling a gap in our knowledge about the evolution of colour vision. Dr Susan Theiss, from the University of Queensland, and colleagues, report their findings in the journal Biology Letters.

The evolution of colour vision has been studied in most vertebrates, but until recently, elasmobranchs (sharks, skates and rays) had been overlooked. Previous physiological research has shown some rays have colour vision but it suggested sharks were colour blind.

These previous studies looked at opsins, which are light-sensitive proteins found in the photoreceptor cells of the retina. Rod opsins are used in low light and produce a black and white image, while cone opsins are used in bright light, and often to see colours. Two or more different types of cone opsins are needed for colour vision.

While some ray species have multiple cone opsins as well as rods, studies in various shark species suggested they had only a single cone visual pigment.

To check whether this really was the case, Theiss and colleagues isolated the visual opsin genes from two wobbegong shark species: the spotted wobbegong Orectolobus maculatus and the ornate wobbegong O. ornatus.

Their findings confirm that wobbegongs possess only one cone opsin, meaning they see the world in shades of grey. The findings help fill in the picture of how colour vision evolved in different species.

"We know the earliest vertebrates had colour vision, but it has been lost by some groups over the course of evolution," says co-author Associate Professor Nathan Hart, a neuroecologist at the University of Western Australia.

PNAS Study: Language Structure Arises from Balance of Clear and Effective Communication

When learning a new language, we automatically organize words into sentences that will be both clearly understood and efficient (quick) to communicate. That’s the finding of a new study reported today in the Proceedings of the National Academy of Sciences (PNAS) which challenges opposing theories on why and how languages come to be organized the way they are.

With more than 5000 languages in the world, it would be easy to assume all vary endlessly, but, in fact, there is great commonality: languages follow only a few recurrent patterns. These commonalities are called “language universals,” a notion suggested in the 1960’s by Noam Chomsky and Joseph Greenberg. A team of researchers from the University of Rochester and Georgetown University Medical Center set out to investigate how these language universals come to be.

Linguists and cognitive scientists have opposing ideas on how a language is developed and shaped. Some believe that languages all derived from a common ancestor; others think that languages vary quite widely and universals do not exist at all. Some have suggested that language universals are an arbitrary evolutionary outcome. The position of the Rochester-Georgetown team is that the human mind shapes a language, even while learning it, based on the need for robust and effective information transfer.

“The thousands of natural languages in our world only have a couple of formats in which they appear, and we are good at understanding and learning languages that have just these formats. Otherwise we could never succeed in learning something so complicated as human languages,” says one of the study’s authors, Elissa L. Newport, Ph.D., a professor in the department of neurology at Georgetown University Medical Center.

Evolution Mostly Driven by Brawn, Not Brains, Analysis Finds

The most common measure of intelligence in animals, brain size relative to body size, may not be as dependent on evolutionary selection on the brain as previously thought, according to a new analysis by scientists.

Brain size relative to body size has been used by generations of scientists to predict an animal’s intelligence. For example, although the human brain is not the largest in the animal kingdom in terms of volume or mass, it is exceptionally large considering our moderate body mass.

Now, a study by a team of scientists at UCL, the University of Konstanz, and the Max Planck Institute of Ornithology has found that the relationship between the two traits is driven by different evolutionary mechanisms in different animals.

Crucially, researchers have found that the most significant factor in determining relative brain size is often evolutionary pressure on body size, and not brain size. For example, the evolutionary history of bats reveals they decreased body size much faster than brain size, leading to an increase in relative brain size. As a result, small bats were able to evolve improved flying maneuvrability while maintaining the brainpower to handle foraging in cluttered environments.

This shows that relative brain size can not be used unequivocally as evidence of selection for intelligence. The study is published in the Proceedings of the National Academy of Sciences.

Why clever crow is no bird brain

Corvus moneduloides, a native of France’s South Pacific territory of New Caledonia, is one of the stars of the avian world.

It uses its beak to craft complex tools from sticks, leaves and other material and then inserts them into deadwood or vegetation to fish out insects and other food.

Researchers led by Jolyon Troscianko of the University of Birmingham in central England used an ophthalmoscope video camera to record field of view and eye movement as three wild-caught birds examined a baited tube.

The bird’s eyes are more forward-positioned, rather than sideways-positioned, which gives it exceptional “binocular overlap,” they found.

This is the area that is viewed by both eyeballs, and is important because it helps the brain judge the distance of nearby objects.

In New Caledonian crows, the binocular overlap is 61.5 degrees, which is at least 23.9 degrees greater than in non-tool-using species of crow that the researchers also examined.

Added to this is the crow’s unusually straight bill, the investigators found.

With it, the bird can get a firm grip on a tool and bring its tip into its field of binocular vision.

"These features enable a degree of tool control that would be impossible in other corvids [crows], despite their comparative cognitive abilities," says the study, published by the journal Nature Communications.

Dolphins, elephants and other birds are among non-primates that have been found to use tools. But the New Caledonian crow occupies a privileged place because its features are so specifically adapted for tools, says the study.

The Date of Interbreeding between Neandertals and Modern Humans

Comparisons of DNA sequences between Neandertals and present-day humans have shown that Neandertals share more genetic variants with non-Africans than with Africans. This could be due to interbreeding between Neandertals and modern humans when the two groups met subsequent to the emergence of modern humans outside Africa. However, it could also be due to population structure that antedates the origin of Neandertal ancestors in Africa. We measure the extent of linkage disequilibrium (LD) in the genomes of present-day Europeans and find that the last gene flow from Neandertals (or their relatives) into Europeans likely occurred 37,000–86,000 years before the present (BP), and most likely 47,000–65,000 years ago. This supports the recent interbreeding hypothesis and suggests that interbreeding may have occurred when modern humans carrying Upper Paleolithic technologies encountered Neandertals as they expanded out of Africa.

Homolog of mammalian neocortex found in bird brain

A seemingly unique part of the human and mammalian brain is the neocortex, a layered structure on the outer surface of the organ where most higher-order processing is thought to occur. But new research at the University of Chicago has found the cells similar to those of the mammalian neocortex in the brains of birds, sitting in a vastly different anatomical structure.

The work, published in Proceedings of the National Academy of Sciences, confirms a 50-year-old hypothesis about the identity of a mysterious structure in the bird brain that has provoked decades of scientific debate. The research also sheds new light on the evolution of the brain and opens up new animal models for studying the neocortex.

"If you want to study motor neurons or dopamine cells, which are biomedically important, you can study them in mammals, in chick embryos, in zebrafish. But for these neurons of the cerebral cortex, we could only do that in mammals before," said Clifton Ragsdale, PhD, associate professor of neurobiology at University of Chicago Biological Sciences and senior author of the study. "Now, we can take advantage of these other experimental systems to ask how they are specified, can they regenerate, and other questions."

Both the mammalian neocortex and a structure in the bird brain called the dorsal ventricular ridge (DVR) originate from an embryonic region called the telencephalon. But the two regions mature into very different shapes, with the neocortex made up of six distinct cortical layers while the DVR contains large clusters of neurons called nuclei.

Night Monkey

A new species of night monkey is one of eight new mammals found during an expedition to northern Peru’s Tabaconas Namballe National Sanctuary (map), scientists announced recently.

A team of Mexican and Peruvian biologists found this “new heaven of unknown biodiversity” during a 2009-2011 expedition, according to a press statement.

Rarely seen and little-studied, night monkeys are listed as vulnerable by the International Union for Conservation of Nature (IUCN) and endangered by the Peruvian government, making the new discovery especially notable.

The as yet unnamed new species was found close to the border of Ecuador, said expedition co-leader Gerardo Ceballos, of the National Autonomous University of Mexico. Compared with two other species of night monkey in the region, the new one has a more uniform color and smaller skull.

(Source: National Geographic)

Science Art-Nature invites you to participate in a juried virtual exhibit, WINDOWS ON EVOLUTION:  An Artistic Celebration of Charles Darwin, commemorating Darwin Day, February 12, 2013.

• The top 40 entries will be posted on Darwin Day, but all qualifying works will eventually be added. 
• The exhibit will remain accessible through the Science Art-Nature website indefinitely. 

We intend to have the exhibit announced through various websites including that of the Darwin Day Organization. Darwin Day, as described there, is “an international celebration of science and humanity.” Visit their site to see videos, lectures on evolution, and information on Darwin, evolution, Darwin Day events and more.

As always, our aim is to display and promote the best contemporary Science Art and to encourage discourse between the scientific and artistic communities.

• Each selected piece of art must portray a narrative about evolution. To help viewers step inside that narrative it must be accompanied by a 100-word caption describing the evolutionary context. For comparable caption examples, please refer to our previous shows in 2010 and 2011. For an example of evolutionary art, see our placeholder for the exhibit.
• The exhibit may be interactive, inviting commentaries from viewers.   Send us your preference!
• The exhibit is open to all living artists working in any medium, although submission of traditional photographs is discouraged.
• Each artist may submit up to three works, but no more than two works from each artist will be selected.

SUBMISSION DATE:  The deadline for entries is midnight, October 15th, 2012.