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Biology & Biomedical Sciences - Global Worming

A worldwide database at UMaine compiles what we know about age-old and newly discovered microinvertebrates

by Aimee Dolloff | Art/Photography by Matthew Hooge

marine worm

Clione sp. (planktonic mollusk) larva, Bocas del Toro, Panama. This image by Matthew Hooge placed 20th in the 2007 Nikon Small World Photomicrography Competition.

Most are no bigger than a speck of dust, yet some have the power to kill fish with their toxic slime. A few are herbivores, but the majority are predators. All have the ability to regenerate any part of their body. First documented in Europe in the early 18th century, new species are still being described at the rate of up to 50 each year.

“To the microscopic world, they’re ferocious dreaded beasts,” says University of Maine biologist Seth Tyler of his favorite invertebrates, marine turbellarians or flatworms, which he has been studying around the world for almost three decades. “They’re like vacuum cleaners going around sucking up other little animals.”

Perhaps even more remarkable is the potential of turbellarians to help answer fundamental questions about the relationships of all animals, including their origins in the primitive Earth and genetic connections to the major branches of the animal kingdom.

“They tell us how animals changed from what we know are the primitive forms, such as jellyfish, to being bilaterally symmetrical,” says Tyler, who started studying turbellarians as a graduate student at the University of North Carolina. “These animals also have a very special type of stem cell. They essentially invented the stem cell among early bilaterally symmetrical animals.”

marine worms

Images left to right, Plagiostomum sp., Belize; Eusyllis sp., California; Acanthodasys sp., Belize; Eumecynostomum evelinae, Brazil; Stomatricha hochbergi, Australia. Photos by Matthew Hooge.

While marine worms come in all shapes and sizes, most of the acoela turbellarians that intrigue Tyler are between 100 micrometers and 300 micrometers long. A few, such as Hofstenia that live in tropical mangrove swamps, can stretch up to 4 millimeters. And while the marine environment is their habitat, their homes can be in sand and mud, on algae and corals, in the interstices of polar marine ice or free-swimming in the water column. Other turbellarians, including the more familiar polyclads and planarians, reach sizes of several inches to as much as 2 feet, and range into freshwater and terrestrial habitats.

However, the size of most turbellarians isn’t proportionate to their role in the ecosystem. As top predators in the microscopic world, they control populations of other microinvertebrates and clean the sands of planktonic organisms that get filtered out of the water by wave action. Indeed, if the acoel turbellarians are as primitive as their genetic connections indicate, then concepts of how the first bottom-crawling animals reproduced and populated new habitats have to be changed, Tyler says.

There are more than 5,000 known species of these invertebrates on the planet and all of them are documented in a database begun in the late 1980s by Tyler and the late Louise Bush of Drew University. Through the years, the data have expanded considerably with the help of taxonomists in Maine and around the world, as well as graduate and undergraduate students and postdocs working in Tyler’s lab.

Because new species frequently are discovered, the task of data collection is seemingly endless. The known species of these worms are probably fewer than 10 percent of the extant species. In the lab, profiling the animals’ morphology includes lots of electron microscopy and confocal laser microscopy — the high-powered means of truly appreciating the remarkable diversity in the features of the tiny invertebrates.

“Many are discovered, but it takes a while to describe them, so that’s the bottleneck,” says Tyler. “Every time we visit a new site, we find undescribed species. Even in Maine, there are still many species of turbellarians yet to be described.

“These, like other marine worms, are still evolving and still adapting to new environments that arrive,” Tyler says.

In 2001 with the help of a more than $754,000 grant from the National Science Foundation, the database was funded as part of research on the systematics of several groups of primitive marine worms. The research was led by Tyler and Wolfgang Sterrer, curator of the Natural History Museum at the Bermuda Aquarium, Museum & Zoo. Sterrer is the world authority not only on several groups of turbellarians, but of the Gnathostomulida, an enigmatic phylum of worms living mostly in anoxic, smelly muds. Seeking examples of all these worm groups — gnathostomulids, acoel and catenulid turbellarians — required far-ranging travel, and so the research team dubbed their project Global Worming.

The online database, which also includes a complete taxonomic listing of all gnathostomulids as well as turbellarians, is providing a single place where all the relevant information on these worms can be stored and used by researchers, reducing the need to search through piles of obscure paper journal articles. The database tracks current concepts of the relationships of these worms to one another and helps those working on phylogenetic relationships of invertebrates gauge their diversity.

“We’ve tried to sample a wide variety, but we feel that we’ve barely scratched the surface of where these animals can be found,” says Tyler. “The thrust with NSF was clarifying the relationship in the taxonomic hierarchy. We’ve been able to understand the relationship of all these families largely from molecular data, and then we use those data to reconstruct how these animals have changed through time — how their strange shapes and peculiar organ systems allowed them to adapt to different habitats.”

Through the years, Tyler’s travels have included Scandinavia and other parts of Europe, Bermuda, the Caribbean, Belize and Panama, western Canada, New Zealand, and Australia to study the lower-level flatworms of the meiofauna or small animal world. Others in his lab have conducted research in Brazil, Thailand, Tanzania, Ethiopia, Honduras, Panama, the Virgin Islands, Australia, China, South Pacific islands, arctic Alaska and Russia.

Researchers from around the world also have made contributions to the database, providing characteristics of worms they’ve discovered, diagnoses, geographic data, links to related literature, free-form notes regarding taxa and images.

Those researchers include Sterrer, whom Tyler describes as “an avid world traveler, chasing worms like this to as many exotic and little-visited places as he can.”

The foundation of the database came from Louise Bush, a zoologist who spent her career studying marine worms and keeping meticulous records of their characteristics and habitats on index cards. While Tyler knew of her research through her publications on turbellarians, it was a postdoctoral researcher in his lab, Julian Smith, who first contacted her about a new species the two of them discovered.

Before her death in 1992 at the age of 84, Bush worked with Tyler to transcribe her extensive collection of handwritten index cards into Global Worming’s digital database.

“She long had a vision of providing access to her database to other scientists through digital connections, and she kept me motivated to accomplish that,” says Tyler. “We’ve made her goal a reality.”

Through the years, a number of students in Tyler’s lab have helped capture Bush’s “massive” manual files for the database. There was also a volunteer, Steve Schilling, a former U.S. Environmental Protection Agency employee for whom biology has always been an avocation.

“I was inspired by Rachel Carson in 1963 as a high school senior,” says Schilling. “I wanted to make a small contribution to the biodiversity crisis.”

Before retiring from the EPA, Schilling worked on an intra-agency project to create a taxonomic list that could easily be used by a variety of federal agencies. He retired from the EPA and moved to Brooksville, Maine, in 1997. A former colleague reminded him that Tyler was one of the experts the EPA contracted with on its taxonomic list project.

“I found Dr. Tyler was a rare combination of a world-class biologist and informatics expert,” says Schilling, who now lives in Colorado and still works on the database, entering information almost daily.

“You don’t know what biodiversity you are losing without the inventory,” he says of the importance of the database.

Also instrumental in the growth of the Global Worming project is former UMaine graduate student and post-doctoral researcher Matthew Hooge, whose contributions to the database have included some spectacular photography of the invertebrate species.

“For many of these worms, Dr. Tyler and I are the only people who have ever viewed them while they’re alive,” he says. “I put a lot of effort into taking digital images that accurately show what the living worms look like, and hopefully capturing how interesting and, often, pretty they are.”

At UMaine, Hooge focused on the systematics of the Acoela. He was the first to explain the phylogenetic relationships of these worms, which, until recently, had simply been pigeonholed into various types without consideration of their evolution.

“This involved describing new species, especially because most of the species I collected in the field were previously unknown to science,” says Hooge, who is now a senior environmental scientist for Wilson Construction Co., in Oregon. He also looked for new physical features in the worms he collected in an effort to help understand the interrelationships of the species.

“I benefited from the project management experience gained while working in Dr. Tyler’s lab to go along with the construction experience I had prior to pursuing a higher degree in biology,” says Hooge, who also continues to make occasional updates to the database.

“There are so many species yet to be described and so much more work to be done,” says Hooge.

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