A Scientist's Life: Greg Rouse

Aboard research vessels and inside Scripps' oceanographic collections, this marine biologist studies the evolution and biodiversity of marine invertebrates

Greg Rouse is a marine biologist at Scripps Institution of Oceanography at UC San Diego. He received a PhD in marine biology from the University of Sydney in 1991, and joined Scripps Oceanography in 2006.

explorations now: What do you do for a living?

Greg Rouse: I'm fortunate enough to be a professor of marine biology and the curator of the Benthic Invertebrate Collection at Scripps Oceanography that houses our collection of backbone-lacking animals that live on the seafloor. I do the normal things a professor does, one of which is to teach. I teach undergraduate and graduate students, mentor graduate students and postdoctoral scholars. In addition I help run one of our four biological collections. We've got over 100 years of samples in the Benthic Invertebrate Collection and I have helped build that up substantially in the 14 years I've been here. Underlying all of that is research. I work on the biodiversity of deep-sea organisms, mostly here in the eastern Pacific margin, but anywhere else I can find them as well.

I've done a lot of work on segmented worms, which are annelids that include earthworms and their relatives. But the vast majority of that group live in the sea. I've worked a lot on their evolutionary relationships and described well over a hundred species of annelids and continue to describe five to 10 new species every year with my students, as it's a good way to introduce them to biodiversity studies.

en: What are some of the main questions in your field?

GR:  For me, one of the fundamental unanswered questions is how many species of animals there are in the ocean, let alone microbes, protists, algae and other plants. We actually do not even have a good ballpark estimate of how many we have yet to find apart from the 300,000 marine animals we've already named. I find undescribed species on every trip and there are many more than we can possibly name with our current methods.

en: Describe some of your current projects.

GR: I’m currently looking at animals that inhabit whale falls, and continuing to work on seadragons. A whale fall is a dead whale on the ocean floor, and this huge resource establishes its own ecosystem that can last for decades. With colleagues at the Monterey Bay Aquarium Research Institute, we’ve discovered and named 18 species of bone-eating worms, called Osedax, in California alone. It is amazing that Osedax species are able to disperse very widely, some species occur world-wide, and yet also radiate in diversity. We want to understand more about the biology of Osedax. How does it eat bone? How do they dissolve the bone? It doesn't have teeth, it has symbiotic bacteria inside its tissue. We're trying to understand that symbiosis.

Another real interest of mine – and the only fish that I've ever worked on – are seadragons. I started working on seadragons in Australia and I brought that project with me here to the U.S. One big discovery that came out of this work was led by my former PhD student Josefin Stiller, and that was the discovery of a third sea dragon species, the ruby seadragon, in 2015. I also collaborate with the Birch Aquarium on its seadragon breeding program.

One of the reasons I got interested in seadragons and their genetics was that I was concerned about their potential decline from wild harvesting and other threats. To better track them, we have created a website called Dragon Search for people to upload photographs they take of seadragons in the wild and even in captivity. We use machine learning to identify those seadragons down to the individual level. It's difficult to know where seadragons are showing up around the world and getting an idea of seadragon diversity through this approach is more fine-grained than genetics. Also, it gets the public involved through citizen science.

en: What are some of the tools you use?

GR: My studies involve expeditions at sea and lab work, so the tools I use vary. I spend days and weeks at sea aboard research vessels, where we use remotely operated vehicles (ROVs) and cameras to explore deep-sea communities. The amazing cameras and technology allow us to look at living animals in their habitat, which is really important. The ROVs also allow us to collect specimens carefully, and we bring them to the surface and observe them in the ship’s lab. We take high-resolution photos of these organisms alive and then we preserve them for anatomy and DNA studies. Those are often frozen and kept in a queue until we can get around to sequencing their DNA and looking at them anatomically.

When we’re ready, we extract the DNA and send it to a lab for sequencing. These days we're moving more into what's called next-generation sequencing where we get a lot of DNA data for every specimen. But I often introduce my students to what's called Sanger sequencing or the traditional sequencing where they do one or two genes at a time. Once we've got those initial sequences, we have a database and we'll just check, is that a match for something we've had before? Does it match in an online archive called GenBank? If it's distinctly different, we know we've got something new. If it matches something, it might be from a new locality, which is really handy to know, or yet another record from the same place. All of these new sequences have a use one way or the other, whether it's something new or just confirming the existence of something we knew already.

en: Why did you come to Scripps?

GR: I was a curator at a museum in Australia and heavily involved in research there. I had been invited over to the U.S. a few times by my colleagues at MBARI to study whale falls, and I was really hooked on that. So when the job was advertised at Scripps Oceanography for a professor who was also a curator, I had the right background to bring the knowledge of how to manage a collection. I was really fortunate enough to get hired here. It was a difficult decision to leave Australia, but the level of deep-sea research and the fantastic facilities at Scripps Oceanography really made that, in the end, an easy decision.

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