Subscribe free to our newsletters via your
. Earth Science News .




Subscribe free to our newsletters via your




















WATER WORLD
Mismatched eyes help squid survive ocean's twilight zone
by Staff Writers
Durham NC (SPX) Feb 14, 2017


The cockeyed squid Histioteuthis heteropsis, also known as the 'strawberry' squid for its pink color and smattering of seed-like photophores, has evolved a mismatched set of eyes: one large eye for seeing the shadows of fellow sea creatures above, and a second small eye for spotting bioluminescent flashes below. Image courtesy Kate Thomas.

From eyes the size of basketballs to appendages that blink and glow, deep-sea dwellers have developed some strange features to help them survive their cold, dark habitat. But with one normal eye and one giant, bulging, yellow eye, the "cockeyed" squid Histioteuthis heteropsis has perhaps the strangest visage of all. "You can't look at one and not wonder what's going on with them," said Duke University biologist Kate Thomas.

By watching cockeyed squids glide and pirouette through more than 150 undersea videos collected by the Monterey Bay Aquarium Research Institute (MBARI), Thomas has gathered the first behavioral evidence that the squids' lopsided eyes evolved to spot two very different sources of light available in the deep sea.

These observations, combined with visual simulations, indicate that the large eye is specifically adapted for gazing upwards, searching for shadows of fellow sea creatures against the rapidly fading sunlight, while the small eye is adapted for gazing downwards, scanning deeper, darker water for flashes of bioluminescence.

"The deep sea is an amazing natural laboratory for eye design, because the kinds of eyes you need to see bioluminescence are different from the kinds of eyes you need to see the basic ambient light," said Sonke Johnsen, professor of biology at Duke University and senior author on the study. "In the case of the Histioteuthis, this cockeyed squid, they chose one eye for each."

The results are published online in a special issue of the journal Philosophical Transactions B.

Also known as the strawberry squid for its bright pink color and smattering of seed-shaped photophores, Histioteuthis lives in a region of the ocean known as the mesopelagic or "twilight" zone, 200 to 1000 meters below the surface.

What meager light reaches these depths is extremely dim, a monochromatic blue, and travels straight down from above. Often, the bioluminescent flashes of other sea creatures - which could signal danger or potential prey - are brighter than the ambient sunlight.

Since their discovery over a century ago, cockeyed squids' mismatched eyes have puzzled biologists.

To gain insight into their behavior, Thomas, a graduate student in Johnsen's lab and lead author on the paper, combed through 30 years of videos collected by MBARI's remotely operated vehicles (ROVs), which documented 152 sightings of Histioteuthis heteropsis and nine sightings of its similar but rarer cousin, Stigmatoteuthis dofleini.

She found that these "lazy, slow-moving" squid prefer to drift through the sea in a pose that might appear upside-down to us land-lubbers - head down and tail up - but nearly vertical, with the big eye consistently oriented upwards, and the small eye consistently oriented downwards.

Using visual simulations, Thomas showed that, because the sunlight only comes from directly above, it would be nearly impossible for an eye angled downwards to spot silhouettes against the ambient light. Similarly, while increasing the size of an upward-facing eye a small amount greatly improves its sensitivity to dim sunlight, increasing the size of a downward-facing eye has little impact on its ability to spot bioluminescent flashes against a dark background.

"The eye looking down really only can look for bioluminescence," Johnsen said. "There is no way it is able to pick out shapes against the ambient light. And once it is looking for bioluminescence, it doesn't really need to be particularly big, so it can actually shrivel up a little bit over generations. But the eye looking up actually does benefit from getting a bit bigger."

Sporting two gigantic eyes may seem like the ultimate strategy for surviving the deep dark sea. But where resources are sparse, the cockeyed squid may have stumbled upon an ingenious solution to an ocular conundrum, Thomas said.

"Eyes are really expensive to make and maintain," Thomas said. "You want eyes just big enough to do what you need to do, but you don't want to have any bigger eyes because then you are just wasting resources."

"Two eyes for two purposes: in situ evidence for asymmetric vision in the cockeyed squids Histioteuthis heteropsis and Stigmatoteuthis dofleini," Kate Thomas, Bruce Robison and Sonke Johnsen. Philosophical Transactions B, Feb. 13, 2017. DOI: # 10.1098/rstb.2016.0069


Comment on this article using your Disqus, Facebook, Google or Twitter login.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Duke University
Water News - Science, Technology and Politics






Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
WATER WORLD
Scientists find huge ancient landslide on Great Barrier Reef
Sydney (AFP) Feb 8, 2017
A massive underwater landslide that could have triggered a towering tsunami some 300,000 years ago has been discovered in the depths of Australia's Great Barrier Reef, scientists said Wednesday. The ancient landslide, likely caused by a strong earthquake that could have generated a tsunami wave 27 metres (90 feet) high, was discovered unexpectedly by researchers conducting three-dimensional ... read more


WATER WORLD
Justice for victims of Nepal's civil war slips away

Myanmar jade mine landslide kills 9: official

Facebook adds tool for helping in times of crisis

Six cosmic catastrophes that could wipe out life on Earth

WATER WORLD
Most stretchable elastomer for 3-D printing

New material that contracts when heated holds great industrial potential

Record-breaking material that contracts when heated

Aavid Thermacore Europe's technology will keep solar satellite cool

WATER WORLD
RE2 Robotics to further develop EOD underwater manipulator system

Litter is piling up on the Arctic sea floor

Study: Deep-sea mining causes long-lasting ecological damage

Splitfin flashlight fish uses bioluminescent light to illuminate plankton

WATER WORLD
Climate change adds to pressures on endangered African penguins

Hidden lakes drain below West Antarctica's Thwaites Glacier

Study shows planet's atmospheric oxygen rose through glaciers

Study shows planet's atmospheric oxygen rose through glaciers

WATER WORLD
China villagers 'beat the Buddha' for a good harvest

Sticky gels turn insect-sized drones into artificial pollinators

Endangered species listing for bumble bee delayed by Trump admin

Syngenta says profits down as ChemChina takeover looms

WATER WORLD
Pacific rim countries to test their tsunami warning system

6 dead after strong quake shakes southern Philippines

Rumbling Indonesian volcano in fresh eruption

Ankara mayor warns of 'manmade quake' threat

WATER WORLD
I. Coast govt pursues bid to end mutiny by elite troops

Ivory Coast govt in bid to end elite troops' mutiny

Somalia to elect president amid security, drought woes

Elite I.Coast troops fire protest shots at two bases

WATER WORLD
Humans subconsciously perceive words as 'round' or 'sharp'

Paleolithic people 'killed' pebbles to rid them of their symbolic power

Chimpanzee feet allow scientists a new grasp on human foot evolution

Baltic hunter-gatherers began farming without influence of migration




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News








The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement