Tuesday, March 19, 2019

Alligators and Birds Hear Like Dinosaurs

University of Maryland (UMD) biologist finds alligators build neural maps of sound the way birds do, suggesting the hearing strategy existed in their common ancestor, the dinosaurs.

To determine where a sound is coming from, animal brains analyze the minute difference in time it takes a sound to reach each ear--a cue known as interaural time difference. What happens to the cue once the signals get to the brain depends on what kind of animal is doing the hearing.

Scientists have known that birds are exceptionally good at creating neural maps to chart the location of sounds, and that the strategy differs in mammals. Little was known, however, about how alligators process interaural time difference.

American Alligators make neural maps of sound the same way birds do.

Credit: Ruth Elsey Louisiana Department of Wildlife and Fisheries

A new study of American alligators found that the reptiles form neural maps of sound in the same way birds do. The research by Catherine Carr, a Distinguished University Professor of Biology at the University of Maryland, and her colleague Lutz Kettler from the Technische Universit√§t M√ľnchen, was published in the Journal of Neuroscience on March 18, 2019.

Most research into how animals analyze interaural time difference has focused on physical features such as skull size and shape, but Carr and Kettler believed it was important to look at evolutionary relationships.

Birds have very small head sizes compared with alligators, but the two groups share a common ancestor--the archosaur--which predates dinosaurs. Archosaurs began to emerge around 246 million years ago and split into two lineages; one that led to alligators and one that led to dinosaurs. Although most dinosaurs died out during the mass extinction event 66 million years ago, some survived to evolve into modern birds.

Carr and Kettler's findings indicate that the hearing strategy birds and alligators share may have less to do with head size and more to do with common ancestry.

"Our research strongly suggests that this particular hearing strategy first evolved in their common ancestor," Carr said. "The other option, that they independently evolved the same complex strategy, seems very unlikely."

To study how alligators identify where sound comes from, the researchers anesthetized 40 American Alligators and fitted them with earphones. They played tones for the sleepy reptiles and measured the response of a structure in their brain stems called the nucleus laminaris. This structure is the seat of auditory signal processing. Their results showed that alligators create neural maps very similar to those previously measured in barn owls and chickens. The same maps have not been recorded in the equivalent structure in mammal brains.

"We know so little about dinosaurs," Carr said. "Comparative studies such as this one, which identify common traits extending back through evolutionary time add to our understanding of their biology."

The research paper "Neural maps of interaural time difference in the American alligator: a stable feature in modern archosaurs," Lutz Kettler and Catherine Carr, was published in the Journal of Neuroscience on March 18, 2019.

This study was supported by the National Institutes of Health (Award No. DCD000436). The content of this article does not necessarily reflect the views of this organization.



Contacts and sources:
Kimbra Cutlip
University of Maryland

Citation:"Neural maps of interaural time difference in the American alligator: a stable feature in modern archosaurs," Lutz Kettler and Catherine Carr, was published in the Journal of Neuroscience on March 18, 2019


Sunday, March 17, 2019

A Cosmic Bat in Flight

Hidden in one of the darkest corners of the Orion constellation, this Cosmic Bat is spreading its hazy wings through interstellar space two thousand light-years away. It is illuminated by the young stars nestled in its core — despite being shrouded by opaque clouds of dust, their bright rays still illuminate the nebula. Too dim to be discerned by the naked eye, NGC 1788 reveals its soft colours to ESO's Very Large Telescope in this image — the most detailed to date.
A Cosmic Bat in Flight
Credit:  ESO

ESO's Very Large Telescope (VLT has caught a glimpse of an ethereal nebula hidden away in the darkest corners of the constellation of Orion (The Hunter) -- NGC 1788, nicknamed the Cosmic Bat. This bat-shaped reflection nebula doesn't emit light -- instead it is illuminated by a cluster of young stars in its core, only dimly visible through the clouds of dust. Scientific instruments have come a long way since NGC 1788 was first described, and this image taken by the VLT is the most detailed portrait of this nebula ever taken.

Even though this ghostly nebula in Orion appears to be isolated from other cosmic objects, astronomers believe that it was shaped by powerful [stellar winds] - from the massive stars beyond it. These streams of scorching plasma are thrown from a star's upper atmosphere at incredible speeds, shaping the clouds secluding the Cosmic Bat's nascent stars.
Hidden in one of the darkest corners of the Orion constellation, this Cosmic Bat is spreading its hazy wings through interstellar space two thousand light-years away.It is illuminated by the young stars nestled in its core — despite being shrouded by opaque clouds of dust, their bright rays still illuminate the nebula. Too dim to be discerned by the naked eye, NGC 1788 reveals its soft colours to ESO's Very Large Telescope in this image — the most detailed to date.

Credit: ESO

NGC 1788 was first described by the German-British astronomer William Herschel, who included it in a catalogue that later served as the basis for one of the most significant collections of deep-sky objects, the New General Catalogue (NGC) [1]. A nice image of this small and dim nebula had already been captured by the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory, but this newly observed scene leaves it in the proverbial dust. Frozen in flight, the minute details of this Cosmic Bat's dusty wings were imaged for the twentieth anniversary of one of ESO's most versatile instruments, the FOcal Reducer and low dispersion Spectrograph 2?(FORS2.

This video pans across NGC 1788. Hidden in one of the darkest corners of the Orion constellation, this Cosmic Bat is spreading its hazy wings through interstellar space two thousand light-years away.

Credit: ESO. Music: Mat Javis — The Shape of Things to Come.

FORS2 is an instrument mounted on Antu , one of the VLT's 8.2-metre Unit Telescopes at the Paranal Observatory, and its ability to image large areas of the sky in exceptional detail has made it a coveted member of ESO's fleet of cutting-edge scientific instruments. Since its first light 20 years ago, FORS2 has become known as "the Swiss army knife of instruments". This moniker originates from its uniquely broad set of functions [2]. FORS2's versatility extends beyond purely scientific uses -- its ability to capture beautiful high-quality images like this makes it a particularly useful tool for public outreach.

ESO is celebrating the twentieth anniversary of one of the VLT’s most versatile instruments, the FOcal Reducer and low dispersion Spectrograph -- FORS2. FORS2 — which was originally accompanied by its twin FORS1 — is an instrument mounted on one of the VLT's 8.2-metre Unit Telescopes at Paranal. Its ability to image large areas of the sky in exceptional detail has made it a coveted member of ESO's fleet of cutting-edge scientific instruments. Since its first light twenty years ago, FORS2 has become known as “the Swiss army knife of instruments”. This moniker originates from its uniquely broad set of functions. FORS2’s versatility extends beyond purely scientific uses — its ability to capture beautiful high-quality images makes it a particularly useful tool for public outreach.

Credit: ESO

This image was taken as part of ESO's Cosmic Gems programme, an outreach initiative that uses ESO telescopes to produce images of interesting, intriguing or visually attractive objects for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations, and -- with the help of FORS2 -- produces breathtaking images of some of the most striking objects in the night sky, such as this intricate reflection nebula. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through the ESO Science Archive ).

This chart shows the location of the reflection nebula NGC 1788 in the constellation of Orion (The Hunter). The map includes most of the stars visible to the unaided eye under good conditions, and the region of sky shown in this image is indicated.
The Cosmic Bat in the Constellation Orion
Credit:  ESO, IAU and Sky & Telescope

Notes:
[1] In 1864 John Herschel published the General Catalogue of Nebulae and Clusters, which built on extensive catalogues and contained entries for more than five thousand intriguing deep-sky objects. Twenty-four years later, this catalogue was expanded by John Louis Emil Dreyer and published as the New General Catalogue of Nebulae and Clusters of Stars (NGC), a comprehensive collection of stunning deep-sky objects.

[2] In addition to being able to image large areas of the sky with precision, FORS2 can also measure the spectra of multiple objects in the night sky and analyse the polarisation of their light. Data from FORS2 are the basis of over 100 scientific studies published every year.


Contacts and sources:
Calum Turner
ESO