Beckman Researcher Justin Rhodes Using Fish for Neuroscience Insights

You won’t find Nemo swimming around in Justin Rhodes’s new marine biology laboratory at the Beckman Institute, but you will find 74 of his real-life clownfish brethren in one of the most unique settings for neuroscience research in the world. 

Almost every child knows the story of Nemo, the digital namesake of the hit movie whose story made clownfish as well-known among kids as 101 Dalmations did for that breed of canine years ago. As compelling as children and many adults found the story of Nemo, the real-life biology of clownfish is just as intriguing to Rhodes for what it might reveal about environmental influences on the evolutionary biology of the brain.

Add in the fact that the Beckman researcher has had a lifelong passion for aquariums and fish and what you get is more than 1,000 gallons of water and a variety of marine life forms in Rhodes’s new marine biology research lab on the third floor of the Institute. Inside are two aquariums housing clownfish for studies and ocean rocks and faux sea anemones to make them feel at home, as well as a special smaller display aquarium featuring an assortment of coral reef fish.

The three aquariums in the remodeled lab space, which was completed in August of 2010, include one 900-gallon system and a 200-gallon system dedicated to the clownfish. The 100-gallon display aquarium abuts a lab window along the third-floor hallway so passers-by can enjoy the six varieties of beautiful and interesting coral reef fish.

“I’ve had aquariums my whole life,” Rhodes said. “I’ve got a big aquarium at home. I’ve loved them since I could talk and I always wanted to be an ichthyologist. This has been my dream.”

Only Rhodes won’t be studying the clownfish the way an ichthyologist might; rather it is the ability to change sex that interests him as a neuroscience researcher. In fact, Rhodes says, if the creators of Finding Nemo had been true to nature, after mom was eaten by a barracuda, dad wouldn’t have gone off looking for his son Nemo; instead, dad would have turned into a mom and then caught the EAC (East Australian Current to the uninitiated) in search of their last living offspring.

“Almost all the coral reef fishes you see change sex; most of them change from female to male but the clownfish changes from male to female,” Rhodes said. “Clownfishes are perfect because they have a very small environment in nature so they are very happy in an aquarium. I’m fascinated by sex change and this is a species that is conducive to being studied in the lab.”

Rhodes’s passion for aquariums and fish predates elementary school, beginning, he says, about age 5. He worked at the American Museum of Natural History in New York City while in high school, single-handedly resurrecting their fish lab. Rhodes later earned a master’s degree in Fisheries at the University of Washington, and then a Ph.D. in Zoology from Wisconsin-Madison. His appointment at the University of Illinois is in the Department of Psychology, Biological Division, and at the Beckman Institute he is a member of the NeuroTech group.

So it’s no surprise that Rhodes initiated a research line studying fish for insights into neuroscience. What is surprising is that he is the only one doing this kind of research using fish as a model organism.

“It’s amazing to me that no one in the world is doing it,” Rhodes said. “There are a few papers done from friends of mine but those are field studies. I’ve confirmed that because I have a friend, John Godwin, who is the guru of the sex change current and he said ‘yeah, it’s a great idea, no one’s doing it’. So it’s very unique.”

The Rhodes Laboratory at Beckman has a research focus on the neurobiology of behavior and on genetics, studying topics like the effects of exercise on the brain and cognition and the causal mechanisms underlying behaviors like addiction.

Rhodes is one of several researchers whose work has shown that the brain undergoes change on an ongoing basis. Rhodes and other Beckman researchers have focused on the effects of exercise on the brain, as part of research demonstrating brain plasticity, or the idea that brain structure is much more plastic and amenable to rewiring than previously thought.

In his previous work Rhodes has used mice as a model for studying how environmental factors such as exercise can change brain structure and behavior, but is now adding the clownfish as a model because of that one amazing capability the species has to change sex.

“It fits the research pattern of trying to understand how the environment and experience of an animal can have long lasting changes in their patterns of behavior,” he said. “This is just a very dramatic example of that where the experience in the brain is actually changing the entire sex of animals engaging in this incredible plasticity.”

Rhodes said he was interested in studying the effects of exercise in mice because the physical activity has been shown to stimulate neurogenesis, or the growth of new brain cells, in an example of the brain’s plasticity. The clownfish offers more opportunities for those types of studies.

“The joke in the lab actually is that, the fish changing sex, now that’s plasticity,” Rhodes said. “I mean that’s an incredible amount of plasticity where the experience and the environment that the animal’s in, through the brain, through the nervous system, is able to completely re-orchestrate, re-program the body and change the morphology. We want to understand how that works, how the brain interprets the change in the social environment and how that’s signaled through hormones.”

Rhodes said another interesting neuroscience topic to explore with the clownfish is sex differences in the brain.

“For example, there are lots of effects of testosterone that are probably not functionally relevant like male-pattern baldness, which is a result of testosterone, but probably has no functional significance,” he said. “How do we figure out what’s functional? It’s difficult. In the fish, though, if we can track the brain changes that occur when an animal is changing from a male to a female, or the other way around depending on the species, we can then find out.”

The new lab is an opportunity for Rhodes to return to his roots by studying fish, but it took the fortuitous arrival of student Derrick Stobaugh to get the project started. Rhodes said Stobaugh was an outstanding undergraduate student in his evolutionary neuroscience class, so he invited him to work in the lab.

“I always send out notices for students to get involved with internships and I mentioned there was one at Woods Hole and he said he was really interested in marine biology,” Rhodes said. “I asked him why and he started telling me how his family had a fish store, and then I met his dad, who is a distributer. So he kept fishes his whole life and he had a lot of great contacts. I bought the whole system through the contact that he had and it was very inexpensive because of that.”

Rhodes said they were able to set up the lab with money left over from his Beckman start-up fund. He designed the layout of the aquarium systems in the lab and a company from Florida built to his specifications and sent them to Illinois. The lab took about four months to set up and, after a hitch or two, the aquariums were up and running and Rhodes had a new research line. He hopes to get future funding for the research line from the National Science Foundation (NSF).

“It’s a novel model organism, which the NSF likes to fund,” he said. “Also, it’s a perfect Beckman opportunity because, to really understand this kind of orchestrated sex change, you need to have multiple investigators looking at it.”

Rhodes plans to collaborate with other researchers, investigating topics such as those involving the pituitary gland, and he is using techniques from his previous work to study new neuron formation in the clownfish.

“We have a specific hypothesis that during sex change this part of the brain called the pre-optic area will grow or reduce the numbers of GnRH neurons,” Rhodes said. “We have some evidence of that from previous studies, but no one has really looked at the growth of new neurons in that part of the brain.”

The display of coral reef fish was created simply to let people know about their work and to let others experience the beauty of an aquarium.

“The fish that I put in there were chosen because they are beautiful but also because they have some interesting biologies,” Rhodes said. “There’s one fish in there that’s a simultaneous hermaphrodite, it has both male testes and ovaries at the same time throughout its entire life. No fresh water fish that we know of changes sex, whereas with marine fishes, it’s very common.”

That meant that if Rhodes wanted to study sex-changing fishes, he was going to have to use marine varieties. He said it has only been in the last 20 years or so that technology reached the point where smaller aquariums could play host to marine fish. What is required, he said, is a really good biological filter. In the marine biology lab, they use blue and green bio-balls, scumbag filters which can be taken out and washed, and a protein skimmer.

The coral reef fish display includes a Red-knobbed Starfish with an interesting feeding method, a Red Lionfish with multi-colored spines, a two-tone Blue Tang with a bright yellow tail fin, a Yellow Tang, a Queen Coris, and a Tobacco Basslet. Rhodes’s passion really comes to the fore when discussing the display fish.

“The lionfish is really interesting because they have those poisonous spines that can paralyze,” he said. “That starfish is really cool because it’s predatory. It’s really fun to see because if you feed it a fish, its stomach actually leaves its body, surrounds the fish, digests it, and then pulls it back in. These starfish can eat clams and things like that, that are completely closed because their stomach can go into tiny little holes and their stomach can go outside their body, into the clam, surround the clam and pull it back out. So it’s fascinating to watch.”

The clownfish aquariums include sea rocks with micro-organisms popping out on some, the faux sea anemones (real-life versions are habitats for the clownfish in their natural setting) and a shell crab in one aquarium. The clownfish not only are used to living in a small environment in the sea but they also live in pairs, as they do in Rhodes’s lab. 

“They’ve been reared in farms so they’re even a bit more likely to be happy to be in aquariums,” he said. “As you can see, all the fish in here are very happy.”