UH research team investigating marine invertebrate larvae

The research will focus on a tube worm that settles onto marine surfaces in warm ocean water and forms masses of hard, calcified tubes.

Shugeng Cao
Shugeng Cao

Shugeng Cao, a natural products chemist and associate professor of pharmaceutical sciences at the Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, is part of a UH research team investigating the mechanisms by which marine biofilm bacteria—bacteria that live in slime films on the surfaces of all objects submerged in the sea—induce the settling of larvae of marine invertebrate animals. A grant totaling more than $870,000 from the Gordon and Betty Moore Foundation will support the work.

With this grant, a UH research team will focus on a small tube worm, Hydroides elegans, that settles onto marine surfaces in warm ocean waters around the world where they form masses of hard, calcified tubes.

In addition to Cao, the team, led by professor Michael Hadfield (Kewalo Marine Laboratory, Pacific Biosciences Research Center, School of Ocean and Earth Science and Technology, UH Mānoa), also includes larval biologist Brian Nedved (Kewalo Marine Laboratory) and microbiologist Rosie Alegado (Center for Microbial Oceanography, Research and Education).

Hydroides elegans tubeworm
A close-up image of the tubeworm Hydroides elegans with its feather-like tentacles extended from its tube. The tentacles both collect microscopic food particles from the water and serve as the place for gas exchange for the worm, passing carbon dioxide from the worm and gaining dissolved oxygen from the water. Photo credit Brian Nedved.

Bacteria initiate dramatic transformation

For more than 100 years, marine biologists have sought an understanding of how the minute larvae of marine invertebrate animals—cast out into the vast ocean–find and settle in the right ecological settings for survival, growth and reproduction.

In the last two decades there has been growing recognition that bacteria are likely the factor that causes many free-floating larvae to settle and transform, yet very little is known of the diversity of bacteria that stimulate larvae to settle and less is known of the mechanisms through which these bacteria act.

“We have isolated specific strains of bacteria from marine biofilms that induce the worm’s larvae to settle and metamorphose,” says Hadfield. “Using these bacteria, our goals are to determine what factors produced by the bacteria cause the larvae to stop swimming, stick to the surface and undergo the dramatic physical changes that make up the process of metamorphosis.”

During the two-year project, Hadfield and colleagues also will study the larva’s receptor or response system. Understanding the relationship between the tube worm and bacteria will shed light on the complex phenomena that lead to the establishment and maintenance of healthy marine seafloor communities throughout the ocean.

Larvae are very particular in selecting surfaces on which they will settle—which is why different communities of invertebrate animals live on sandy beaches, rocky coasts, pilings and other surfaces in enclosed harbors.

“For many—probably most–of these animals, biofilm bacteria are the key,” Hadfield explains. “This research holds promise to reveal the basis for differential larval settlement in the sea.”

Read more about the research at UH System News.