||Just before COVID-19 reared its ugly head here in the states, I came across a university lab doing some fascinating cichlid research on breeding behavior. Using Astatotilapia burtoni, a maternal mouthbrooder from Lake Tanganyika in Africa, as the model fish for the research, Dr. Scott Juntti’s lab is attempting to unlock some of the mysteries surrounding A. burtoni breeding behavior.
Dr. Juntti became interested in neuroscience as an undergraduate at the University of Wisconsin, where he fell in love with life in the lab. After completing his undergraduate work, including stops at labs in Germany and San Diego, he began his graduate work at the University of California, San Francisco. There he began working in Dr. Nirao Shah’s lab, where he studied social behavior using molecular genetic approaches in mice.
Upon completion of his graduate studies, Dr. Juntti moved to Stanford where he did his postdoc work with renowned cichlid researcher Dr. Russ Fernald. There he applied the techniques he used in mice studies to cichlid fish and ultimately became fascinated with this family of fishes. In 2017, he set up his own lab at the University of Maryland, College Park, where he combines evolutionary biology and neuroscience techniques to unlock the mysteries of the social brain in cichlids.
Time to get started!
Please describe your lab to the readers – your tanks, filtration, lighting, etc.
Our fish are housed in a recirculating system with ~100 tanks of 32-120 liter capacity and another ~100 tanks of 1-2 liters for larval or juvenile ages. Filtration is accomplished in centralized pump/filtration systems with a fluidized bed filter and various others to get rid of all the waste material. We keep fish under full-spectrum LEDs.
Your model cichlid species is Astatotilapia burtoni from Lake Tanganyika. Can you summarize for the readers your research using these fish?
We’re interested in social behavior, particularly in how animals decide who to mate with and when. We think this is a good approach to understand some basic rules about how information is processed by the nervous system, because these instinctive behaviors require little learning. This implies that genetic experiments can help us understand the nature of these behaviors. In addition, there’s evidence that picky females are a key driver of speciation. If we can understand how the brain selects a mate, we’ll uncover an important part of the reason that there are so many cichlid species.
One of the tools we put to use is CRISPR gene editing, which allows us to test whether a given gene is important by mutating it. Much of our work focuses on hormone signaling systems that signal reproductive status (think testosterone, estrogen, and progesterone). One gene, a receptor for a hormone called prostaglandin F seems to be particularly important for females deciding when to mate. This hormone’s levels rise in the blood after ovulation causes the oviduct to stretch with eggs. In fact, this same hormone signals in humans as a fetus grows in humans and causes stretch in the cervix. In fish, it seems to tell the brain “You’ve got eggs to lay, go out and find a mate.” Incredibly, after we mutate this gene, females never initiate mating. We think this result gives us a great lead to figure out how the brain takes in all the signals from prospective mates and incorporates reproductive status when deciding when to mate.
What do you find most fascinating about the complex social behaviors exhibited by this fish, commonly referred to as Burton’s mouthbrooder?
How do they find the right mate in an environment as busy as Lake Tanganyika?
Are there any phenotypic traits in A. burtoni that are predictors of its social behavior that might also be predictors in other cichlid species? If so, can you comment on that?
The extreme sex differences in color are predictive of a suite of behaviors that include promiscuous mating and lack of parental care. Evolutionarily speaking, males seem to have invested more in wooing females than sticking with their offspring.
Many species of African cichlids are mouthbrooders. What are some other cichlid species besides A. burtoni that you would like to work with and why?
I’d love to work with species that are male mouthbrooders. What’s different about their brains that makes them stick around to raise their young?
You did your postdoc work under Dr. Russell Fernald at Stanford. In August of last year, I interviewed Dr. Hans Hofmann from the University of Texas, who also did his Postdoc work under Dr. Fernald. Hofmann also uses Burton’s mouthbrooder in his research. Are you familiar with his work? If so, can you comment on how his work might be complementing your own or vice versa?
Hans does terrific work that pushes the envelope in terms of demonstrating what cichlid brains are capable of. It really should make people reconsider the idea that fish are “lower” vertebrates. They’ve evolved highly advanced behavioral skills!
How might your efforts inform hobbyists who keep Burton’s mouthbrooder or other mouthbrooding species?
Hopefully it makes them think about the reproductive cycle of females. Male haplochromines get all the attention due to their beautiful colors, but female mate choice is really fascinating.
Your work with fish, like many other researchers, often requires that you euthanize them. How to do this humanely is often misunderstood by hobbyists who have sick or dying fish. Can you comment on effective, humane methods hobbyists can employ when they need to euthanize a fish?
We follow generally accepted protocols that utilize the anesthetic tricaine to euthanize them. We try to be as quick as we can about sacrificing them.
I’ve always felt that traditional ecological knowledge (derived from hobbyists and, say, long time fishermen) and scientific ecological knowledge (derived from scientists and researchers) can complement each other. I call this experience versus experimentation. What ways can you see fish hobbyists contributing to the landscape of discovery that is often confined to science?
There’s a lot of hybridization that occurs in the fish trade to get “improved” colors. It would be really interesting to know which species interbreed readily. Can this be predicted simply by time since their common ancestor? Or are there other factors at play?