Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Deep-sea crabs grab grub using UV vision

06.09.2012
Crabs living half-a-mile down in the ocean, beyond the reach of sunlight, have a sort of color vision combining sensitivity to blue and ultraviolet light. Their detection of shorter wavelengths may give the crabs a way to ensure they grab food, not poison.

"Call it color-coding your food," said Duke biologist Sönke Johnsen. He explained that the animals might be using their ultraviolet and blue-light sensitivity to "sort out the likely toxic corals they're sitting on, which glow, or bioluminesce, blue-green and green, from the plankton they eat, which glow blue."

The discovery explains what some deep-sea animals use their eyes for and how their sensitivity to light shapes their interactions with their environment. "Sometimes these discoveries can also lead to novel and useful innovations years later," like an X-ray telescope which was based on lobster eyes, said Tamara Frank, a biologist at Nova Southeastern University. She and her collaborators report their findings online Sept. 6 in the Journal of Experimental Biology.

Frank, who led the study, has previously shown that certain deep-sea creatures can see ultraviolet wavelengths, despite living at lightless depths. Experiments to test deep-sea creatures' sensitivity to light have only been done on animals that live in the water column at these depths. The new study is one of the first to test how bottom-dwelling animals respond to light.

The scientists studied three ocean-bottom sites near the Bahamas. They took video and images of the regions, recording how crustaceans ate and the wavelengths of light, or color, at which neighboring animals glowed by bioluminescence. The scientists also captured and examined the eyes of eight crustaceans found at the sites and several other sites on earlier cruises.

To capture the crustaceans, the team used the Johnson-Sea-Link submersible. During the dive, crustaceans were gently suctioned into light-tight, temperature-insulated containers. They were brought to the surface, where Frank placed them in holders in her shipboard lab and attached a microelectrode to each of their eyes.

She then flashed different colors and intensities of light at the crustaceans and recorded their eye response with the electrode. From the tests, she discovered that all of the species were extremely sensitive to blue light and two of them were extremely sensitive to both blue and ultraviolet light. The two species sensitive to blue and UV light also used two separate light-sensing channels to make the distinction between the different colors. It's the separate channels that would allow the animals to have a form of color vision, Johnsen said.

During a sub dive, he used a small, digital camera to capture one of the first true-color images of the bioluminescence of the coral and plankton at the sites. In this "remarkable" image, the coral glows greenish, and the plankton, which is blurred because it's drifting by as it hits the coral, glows blue, Frank said.

That "one-in-a-million shot" from the sub "looks a little funky," Johnsen noted. But what it and a video show is crabs placidly sitting on a sea pen, and periodically picking something off and putting it in their mouths. That behavior, plus the data showing the crabs' sensitivity to blue and UV light, suggests that they have a basic color code for their food. The idea is "still very much in the hypothesis stage, but it's a good idea," Johnsen said.

To further test the hypothesis, the scientists need to collect more crabs and test the animals' sensitivity to even shorter wavelengths of light. That might be possible, but the team will have to use a different sub, since the Johnson-Sea-Link is no longer available.

Another challenge is to know whether the way the crabs are acting in the video is natural. "Our subs, nets and ROVs greatly disturb the animals, and we're likely mostly getting video footage of stark terror," Johnsen said. "So we're stuck with what I call forensic biology. We collect information about the animals and the environment and then try to piece together the most likely story of what happened."

Here, the story looks like the crabs are color-coding their food, he said.

Citations:

Light and vision in the deep-sea benthos I: Vision in Deep-sea Crustaceans. Frank, T., Johnsen, S. and Cronin, T. (2012). Journal of Experimental Biology. DOI: 10.1242/jeb.072033

Light and vision in the deep-sea benthos II: Bioluminescence at 500-1000 m depth in the Bahamian Islands. Johnsen, S., et. al. (2012). Journal of Experimental Biology. DOI: 10.1242/jeb.072009

Karl Bates | EurekAlert!
Further information:
http://www.duke.edu

More articles from Life Sciences:

nachricht Molecular microscopy illuminates molecular motor motion
26.07.2017 | Penn State

nachricht New virus discovered in migratory bird in Rio Grande do Sul, Brazil
26.07.2017 | Fundação de Amparo à Pesquisa do Estado de São Paulo

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

CCNY physicists master unexplored electron property

26.07.2017 | Physics and Astronomy

Molecular microscopy illuminates molecular motor motion

26.07.2017 | Life Sciences

Large-Mouthed Fish Was Top Predator After Mass Extinction

26.07.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>