Ohio State University

The phases of a greater wax moth.

By Tia Ghose
LiveScience

The ubiquitous greater wax moth is ordinary in every way but one: It has the ability to hear the highest-known sound frequency.

The greater wax moth's hearing goes up to about 300 kilohertz, nearly 100 kHz higher than the hearing of some bats.

"This is the animal with the highest frequency sensitivity yet recorded, there's no other animal that can hear such a high frequency," said study co-author James Windmill, a bioacoustician at the University of Strathclyde in Scotland.

The moth's ultrasonic hearing range, which was described Tuesday in the journal Biology Letters, could help the creature hear the sonar communication of their predators, bats, Windmill said. [Flying Mammals: Gallery of Amazing Bats]

Humble moth
The nondescript brown moth species, Galleria mellonella, lives in North America, Europe and Asia and has a 1.1-inch (3-centimeter) wingspan. Its tiny ear is just 0.02 inches (0.5 millimeters) across.

Other researchers had tested the hearing of the greater wax moth, but gave up at about 100 kHz. But the moth's ear was so sensitive at that frequency that Windmill and his colleagues wondered just how high they could hear. (By comparison, the human ear can hear sounds up to just 20 kHz)

The research team used a laser vibrometer to measure the vibrations of the ear in response to sound waves. They also measured electrical signals in the ear nerve.

They then watched the ear as they raised the sound frequency higher and higher.

The researchers found that the moth's hearing went to an astonishing 300 kHtz.

Bat versus moth
The team hypothesizes that the moth's ultrasonic hearing could help it evade their predators in many environments.

The moth "would probably be the food for many different bats using many different frequencies," Windmill told LiveScience.

Bat echolocation calls can go as high as 212 kHz, so the high-frequency hearing could help the greater wax moth hear a different predator species' calls and evade them, Windmill said.

The other possibility is that their ears help females hear the mating calls of males.

Though male mating calls are at a lower pitch (about 80 kHz), they are incredibly short pulses. Because of how hearing works, an ear tuned to the lower pitch of the mating calls would still be moving in response to one pulse when the second was made. Being tuned to a higher frequency range could allow the females to differentiate the individual pulses, Windmill said.

Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

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Ryan Kempster

Baby brown-banded bamboo sharks (Chiloscyllium punctatum) still developing within leathery egg cases can sense the electric fields of predators and freeze in place to avoid detection, researchers report online Wednesday in the journal PLoS ONE.

By Charles Choi
LiveScience

Baby sharks still developing within leathery egg cases can sense the electric fields of predators and freeze in place to avoid detection, researchers say.

These findings could help in developing more effective shark repellents, scientists said.

A number of species of sharks deposit embryos in rectangular capsules once whimsically called mermaid's purses or devil's purses. These egg cases often possess long tendrils at each corner that help anchor them to surfaces.

The shark parents of these embryos use highly sensitive receptors known as the ampullae of Lorenzini to detect the electric fields generated by the muscle contractions of potential prey. Now scientists find their embryos can similarly detect the electric fields of potential predators to help them escape being eaten.

The researchers focused on the brown-banded bamboo shark (Chiloscyllium punctatum). Their embryos spend up to five months inside egg cases, where they are vulnerable to attack from fish, marine mammals and even large mollusks.

The investigators discovered that even within their egg cases, the embryos could apparently detect electric fields in the lab created to mimic those of predators such as fish. Video recordings showed the developing shark babies responded by ceasing all movements of their gills and keeping their bodies perfectly still. [See Video and Images of Developing Bamboo Sharks]

Learning more about such behaviors may help researchers develop effective shark repellents, ones that generate electric fields that sharks keep away from, said researcher Ryan Kempster, a marine neuroecologist at the University of Western Australia.

"There are a variety of commercially available, nonlethal electric shark repellents, but the scientific data supporting their effectiveness is limited," Kempster told LiveScience. This line of research helps analyze what reactions different species of sharks have toward predatorlike electric fields and how these responses might or might not change over time.

Although shark attacks attract attention worldwide, humans are far more dangerous to sharks than sharks are to humans.

"As founder of the shark conservation group Support Our Sharks, a driving force behind my work is not only in producing a repellent to protect ocean users from potential attack, but also to protect sharks from being killed," Kempster said.

"In an attempt to make the ocean a safer place, governments in western Australia, Hawaii and France's Reunion Island have previously implemented pre-emptive killing of sharks. Given the crucial role that sharks play in ocean ecosystems, I believe it is much more appropriate to take advantage of nonlethal shark-control measures instead."

Shark numbers are decliningrapidly worldwide, mostly as a result of accidental catches in fishing nets. An electric shark repellant may also help reduce such catches "by keeping sharks away from fishing gear, to decrease the number of sharks unnecessarily killed each year," Kempster said.

The scientists detailed their findings online Wednesday in the journal PLOS ONE.

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Dmitry Bogdanov

Paleontologists have identified one of the world's oldest known "super predators," meaning carnivores that can feed on prey that's as big or bigger than themselves.

By Jennifer Viegas
Discovery

Paleontologists have identified one of the world's oldest known "super predators," meaning carnivores that can feed on prey that's as large, or larger, than themselves.

The toothy beast, described in the latest issue of the Journal of Systematic Paleontology, was a marine crocodile that looked part shark and part sinister dolphin. Its scientific name is Tyrannoneustes lythrodectikos, or "Tyrant Swimmer."

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"Tyrannoneustes lythrodectikos is the oldest known metriorhynchid macrophage — an animal that was adapted to feeding on large-bodied prey," lead author Mark Young of the University of Edinburgh's School of Biological Sciences told Discovery News.

He explained that the term "metriorhynchid" refers to a group of marine crocodiles that were superficially similar to living dolphins.

"They lacked bony armor, had flipper-like forelimbs and had a tail fluke," he said.

This animal evolved from related species "that were opportunistic predators of small, fast moving prey." These marine hunters had narrow snouts and multiple teeth, but the teeth weren't serrated like those of Tyrant Swimmer, which also could open its mouth very wide.

Young and his colleagues studied the remains of Tyrant Swimmer, found in the Oxford Clay Formation. This is a Jurassic marine sedimentary rock formation underlying much of southeast England. The remains have been in storage for some time at the Hunterian Museum in Glasgow.

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The super predator made the rounds outside of what is now the U.K. too.

"Tyrannoneustes is known from shallow marine deposits across Europe (England, France and Poland)," Young, who also works at the University of Southhampton's National Oceanography Center, explained. "During the Middle Callovian 165 million years ago, much of Europe was covered by a shallow sea, creating a chain of large to small islands. Tyrannoneustes lived in this shallow sea, along with numerous other marine reptiles."

These reptiles included pliosaurs, plesiosaurs and ichthyosaurs. Giant pliosaurs were even larger than the Tyrant Swimmer, so they might have feasted on the formidable species. As its name suggests, however, Tyrant Swimmer would have been swift in the water, so it likely could have out-swam possible predators and used the swimming prowess to capture its own prey.

As of now, no stomach contents for the Tyrant Swimmer have been located, so what it precisely ate remains a mystery.

The Middle Jurassic gave rise to other huge predators in both the sea and on land. One of the most bloodthirsty dinosaurs of the time was Allosaurus, known for its massive toothy skull on a short neck. Some dinosaurs of this genus could grow up to 28 feet long.

As for ecosystems today, the presence of such big hunters usually indicates a healthy food chain, with many animals down the line for predators to prey upon. When keystone species begin to decline, usually the entire ecosystem is in trouble.

"It is great to see old collections (specimens collected in the 1800s) being re-examined, and it demonstrates the scientific value of museum collections," Lorna Steel, a curator in the Department of Paleontology at the Natural History Museum in London, told Discovery News.

In terms of what happened to Tyrant Swimmer, Young indicated it evolved into an even more stealthy group of marine predators with very large and numerous teeth and mouths that could open extremely wide.