Sunday, March 29, 2015
YOLO COUNTY NEWS
99 CENTS

Study: Turbulence tells sea urchins to settle in

Microscopic purple sea urchin larvae drift in the upper levels of the ocean for about a month before settling on a rocky shore and transforming into the familiar spiny adult. Researchers at UC Davis' Bodega Marine Laboratory have found that ocean turbulence plays a key role in the larvae's life cycle. Jason Hodin, Stanford University Hopkins Marine Station/Courtesy photo

By
From page A6 | April 18, 2013 |

Tumbling in the waves as they hit a rocky shore tells purple sea urchin larvae it’s time to settle down and look for a spot to grow into an adult, researchers at UC Davis’ Bodega Marine Laboratory have found.

“How these animals find their way to the right habitat is a fascinating problem,” said Brian Gaylord, a professor of evolution and ecology. “The turbulence response allows them to tell that they’re in the right neighborhood.”

Like most shoreline animals, purple sea urchins have a two-stage life cycle. The young are microscopic, look completely different from adults and drift in the upper levels of the ocean for about a month before settling on a rocky shore and transforming into the familiar spiny adult.

“Once they decide to settle, they attach to a rock and undergo body remodeling into a juvenile sea urchin with spines,” Gaylord said.

Over short distances, the larvae can respond to chemical traces in the water, especially substances that might be given off from a rock thick with algae or other food for the growing urchins.

But how do the larvae know they are close enough to the right shoreline habitat to start searching for such signals?

On the California coast, rocky headlands — the urchins’ preferred environment — are interspersed with long stretches of beach that experience lower levels of turbulence. The larvae don’t have the resources to swim for miles along a beach looking for a nice slimy rock, but when carried by currents near a wave-swept rocky reef, the high turbulence tells them to begin a finer-scale search, the researchers found.

Gaylord and co-authors Jason Hodin of Stanford University’s Hopkins Marine Station and Matthew Ferner of San Francisco State University used a device called a Taylor-Couette cell to see how urchin larvae responded to being churned by shear forces comparable to those in waves breaking on a rocky shore.

The Taylor-Couette cell consists of one rotating cylinder inside another, with a layer of fluid in between. When the cylinders spin relative to each other, they set up shear forces in the fluid. Scientists more typically use the device for studying fluid dynamics, especially the transition where flows becomes chaotic and turbulence appears.

Gaylord and his colleagues took the urchin larvae for a spin through a Taylor-Couette cell then exposed them to potassium, known to act as a chemical signal that triggers larvae to begin settling.

Larvae that had been exposed to turbulence responded to the chemical signal earlier in development than those that had not — in fact, they responded at a stage at which it had previously been believed larvae could not settle.

Especially telling was that neither turbulence nor the chemical signal alone promoted settling at this earlier developmental stage.

The experiment shows that the shift from living free in the ocean to living on a rock is a two-step process, Gaylord said. In the first step, exposure to turbulence initiates an abrupt transition to a state in which the larvae are “competent to settle.” A chemical signal triggers the second step, actual settlement, and the larvae then complete their transformation into juvenile sea urchins.

It’s not yet clear how the larvae detect turbulence, Gaylord said. That might happen through receptors that respond to stretching or flexing. The two-step settlement process might occur in other species that settle on shorelines, he said.

The work appears in the journal Proceedings of the National Academy of Sciences.

— UC Davis News Service

Comments

comments

  • Recent Posts

  • Enter your email address to subscribe to this newspaper and receive notifications of new articles by email.

  • .

    News

    Where do Davis recyclables go?

    By Felicia Alvarez | From Page: A1 | Gallery

     
    UCD faculty receive lowest pay in the system

    By Tanya Perez | From Page: A1

    Motive for murder-suicide remains a mystery

    By Lauren Keene | From Page: A1, 1 Comment | Gallery

     
    Davis sewage to get new digs

    By Dave Ryan | From Page: A1

    Human Relations Commission hosts Chávez celebration

    By Special to The Enterprise | From Page: A2

     
     
    Davis Flower Arrangers meet Wednesday

    By Enterprise staff | From Page: A6

    ‘Music as Medicine’ is radio show topic

    By Enterprise staff | From Page: A6

     
    Friendship the topic on radio program

    By Enterprise staff | From Page: A6

     
    .

    Forum

    These results were meaningless

    By Letters to the Editor | From Page: B4

     
    Survey not representative

    By Letters to the Editor | From Page: B4

    Answers on the green waste program

    By Special to The Enterprise | From Page: B4

     
    A phone call could have fixed this

    By Special to The Enterprise | From Page: B4

    Milt Prigee cartoon

    By Special to The Enterprise | From Page: B4

     
    Some ‘survey’ …

    By Letters to the Editor | From Page: B4

    Mayor’s corner: Looking ahead to spring

    By Dan Wolk | From Page: B5 | Gallery

     
    A Little Respect for Dr. Foster

    By Nicholas Kristof | From Page: B5

    Universities need more funding

    By Special to The Enterprise | From Page: B5

     
    Father of the bride snubbed

    By Special to The Enterprise | From Page: A8

    Which experiences count as ‘once in a lifetime’?

    By Marion Franck | From Page: A8

     
    After a month of no TV news, I’m feeling much better

    By Debra DeAngelo | From Page: A8

    Take a hike for your heart

    By Special to The Enterprise | From Page: A8

     
    .

    Sports

    Aggie softball splits doubleheader

    By Enterprise staff | From Page: B1

     
    Davis softballers suffer setback, remain optimistic

    By Enterprise staff | From Page: B1

    Republic stun Galaxy with repeated history

    By Enterprise staff | From Page: B1

     
    Bad fourth quarter sinks boys lacrosse

    By Enterprise staff | From Page: B1

    Aggies’ walkoff win clinches series against Riverside

    By Enterprise staff | From Page: B1 | Gallery

     
    Burns scores shootout winner to lift Sharks

    By The Associated Press | From Page: B2 | Gallery

    UCD roundup: Aggie women’s tennis dominates at home

    By Enterprise staff | From Page: B10 | Gallery

     
    .

    Features

    .

    Arts

    .

    Business

    Millennials are changing our community

    By Rob White | From Page: A9

     
    With new owner, DAC will Get Fit

    By Wendy Weitzel | From Page: A9 | Gallery

    Grant writing for non-profits workshop set

    By Special to The Enterprise | From Page: A9

     
    .

    Obituaries

    .

    Comics

    Comics: Sunday, March 29, 2015

    By Creator | From Page: B8