Posts tagged mammals
Articles and news from the latest research reports.
Super-sensory hearing?
The discovery of a previously unidentified hearing organ in the South American bushcrickets’ ear could pave the way for technological advancements in bio-inspired acoustic sensors research, including medical imaging and hearing aid development.
Researchers from the University of Bristol and University of Lincoln discovered the missing piece of the jigsaw in the understanding of the process of energy transformation in the ‘unconventional’ ears of the bushcrickets (or katydids).
Bushcrickets have four tympana (or ear drums) – two on each foreleg; but until now it has been unknown how the various organs connect in order for the insect to hear. As the tympana (a membrane which vibrates in reaction to sound) does not directly connect with the mechanoreceptors (sensory receptors), it was a mystery how sound was transmitted from air to the mechano-sensory cells.
Sponsored by the Human Frontiers Science Program (HFSP), the research was developed in the lab of Professor Daniel Robert, a Royal Society Fellow at the University of Bristol. Dr Fernando Montealegre-Z, who is now at the University of Lincoln’s School of Life Sciences, discovered a newly identified organ while carrying out research into how the bushcricket tubing system in the ear transports sound. The research focussed on the bushcricket Copiphora gorgonensis, a neotropical species from the National Park Gorgona in Colombia, an island in the Pacific. Results suggest that the bushcricket ear operates in a manner analogous to that of mammals. A paper detailing this remarkable new breakthrough is published in the journal, Science.
New Study Shows Effects of Prehistoric Nocturnal Life on Mammalian Vision
Since the age of dinosaurs, most species of day-active mammals have retained the imprint of nocturnal life in their eye structures. Humans and other anthropoid primates, such as monkeys and apes, are the only groups that deviate from this pattern, according to a new study from The University of Texas at Austin and Midwestern University.
The findings, published in a forthcoming issue of Proceedings of the Royal Society B, are the first to provide a large-scale body of evidence for the “nocturnal bottleneck theory,” which suggests that mammalian sensory traits have been profoundly influenced by an extended period of adaptation to nocturnality during the Mesozoic Era. This period lasted from 250 million years ago to 65 million years ago.
To survive in the night, mammals had a host of visual capabilities, such as good color vision and high acuity, which were lost as they passed through the nocturnal “bottleneck.”
The songs of whales and dolphins can be beautiful to the ear. Now acoustics engineer Mark Fischer has created a way to make them visually pleasing too. What’s more, his technique captures more information about the sound than traditional ways of visualising whalesong.
The Neuronal Organization of the Retina
The mammalian retina consists of neurons of >60 distinct types, each playing a specific role in processing visual images. They are arranged in three main stages. The first decomposes the outputs of the rod and cone photoreceptors into ∼12 parallel information streams. The second connects these streams to specific types of retinal ganglion cells. The third combines bipolar and amacrine cell activity to create the diverse encodings of the visual world—roughly 20 of them—that the retina transmits to the brain. New transformations of the visual input continue to be found: at least half of the encodings sent to the brain (ganglion cell response selectivities) remain to be discovered. This diversity of the retina’s outputs has yet to be incorporated into our understanding of higher visual function.
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)
Duchess the elephant has UK’s first cataract op
Zookeepers are carefully monitoring an elephant who was the first in the UK to undergo an eye operation, to discover how much of her sight has returned.
Duchess was said to be recovering well after yesterday’s operation to remove a cataract from her left eye.
Paignton Zoo’s 42-year-old African elephant had her right eye removed in 2011 because of glaucoma, and has lately become practically blind.
Neil Bemment, curator of mammals and director of operations at the zoo, said staff had high hopes for the operation’s success. “It couldn’t have gone better,” he said. “She went down very smoothly under the anaesthetic and the operation went as well as we could hope.”
Mr Bemment said Duchess was still “disorientated” from the procedure and was being kept out of view with plenty of reassurance from staff.
"Her sight had deteriorated to the point where she could only tell the difference between light and shade," Mr Bemment said. "We’re hoping that his will restore her sight for most distances. She won’t be able to read about herself in the newspaper, but we’re hopeful that she will be more familiar in her surroundings."
(Source: thisisdevon.co.uk)
A glance at a star-nosed mole (Condylura cristata) is enough to convince most people that something very strange has evolved in the bogs and wetlands of North America. There’s nothing else on the planet quite like this little palm-sized mammal. Its nose is ringed by 22 fleshy appendages, called rays, which are engorged with blood and in a constant flurry of motion when the animal searches for food.
What is this star? How did it evolve and what is it for? What advantage would be worth sporting such an ungainly structure? To a neuroscientist interested in sensory systems, this kind of biological anomaly represents an irresistible mystery. I first began studying star-nosed moles in the early ’90s in an attempt to answer some of these basic questions. But I soon discovered that this unusual animal, like many other specialized species, could reveal general principles about how brains process and represent sensory information. In fact, star-nosed moles have been a gold mine for discoveries about brains and behavior in general—and an unending source of surprises. The most obvious place to start the investigation was with that bizarre star.
(Source: the-scientist.com)
Palaeontologists from the University of Zurich have “rediscovered” a skull bone that was thought to have been lost during the course of evolution for many mammals.
Mammals’ skulls are composed of around 20 bones — fewer than those of fish, reptiles and birds. This is because when mammals evolved from reptile-like vertebrates 320 million years ago, the skull structure simplified. Some bones were lost in the process, particularly some of the skull roof bones. The interparietal is one such bone, but it has perplexed researchers since it had survived in some mammals, such as horses and cats (and 2.8 percent of humans) but not in others.
The interparietal is clearly discernible in the embryo, but fuses with other bones beyond recognition shortly afterwards. As a result it’s often been missed. However, new imaging techniques have been able to detect its presence in all mammals.
How Low Can You Go? Physical Production Mechanism of Elephant Infrasonic Vocalizations
Elephants can communicate using sounds below the range of human hearing (“infrasounds” below 20 hertz). It is commonly speculated that these vocalizations are produced in the larynx, either by neurally controlled muscle twitching (as in cat purring) or by flow-induced self-sustained vibrations of the vocal folds (as in human speech and song). We used direct high-speed video observations of an excised elephant larynx to demonstrate flow-induced self-sustained vocal fold vibration in the absence of any neural signals, thus excluding the need for any “purring” mechanism. The observed physical principles of voice production apply to a wide variety of mammals, extending across a remarkably large range of fundamental frequencies and body sizes, spanning more than five orders of magnitude.
Read more here