Dr. Lauren Nadler, Assistant Professor in the Department of Marine and Environmental Sciences at Nova Southeastern University, explains how parasites can be energetically costly, even before infection, in her paper “A brain-infecting parasite impacts host metabolism both during exposure and after infection is established.” Dr. Nadler further discusses how she became involved in ecology, and why she enjoys the field.

Dr. Lauren Nadler at the Lizard Island Research Station in Australia (photo credit Shaun Killen).
Dr. Lauren Nadler at the Lizard Island Research Station in Australia (photo credit Shaun Killen).

About the paper

What’s your paper about?

We wanted to take a slightly unusual vantage point for our paper when looking at the potential energetic costs of parasites on hosts. While most research to date examines how hosts are impacted after infection becomes established, our group wanted to see if parasites can drain energy from their hosts even before infection, during the time point when hosts first encounter parasites in their environment, but they have yet to take hold with a full-blown infection. Before our study, only one previous study had investigated this idea, and it studied a fruit fly host.

A euthanized California killifish (Fundulus parvipinnis) with its brain exposed, revealing its infection with the trematode parasite Euhaplorchis californiensis. Each of the small dots visible on the brain is an individual parasite. (photo credit Lauren Nadler).
A euthanized California killifish (Fundulus parvipinnis) with its brain exposed, revealing its infection with the trematode parasite Euhaplorchis californiensis. Each of the small dots visible on the brain is an individual parasite. (photo credit Lauren Nadler).

We exposed California killifish to infectious stages of a parasite that—when it fully settles in the host—resides on the host’s brain and modifies its behaviour to increase its chance of predation by the fish´s primary predators (and the next host in the parasite´s life cycle), fish-eating marsh birds. When confronted by the parasite’s infectious stages, the fish were more active and burned more energy. This makes a lot of sense, as by enacting “behavioural defences” — say, by scratching off parasites when they first land on the skin, before burrowing in — hosts may burn extra energy dealing with parasites even before the parasites have established within the host.

In the wild, these killifish encounter thousands of these parasites nearly continuously throughout their lives. Therefore, these encounters could markedly impact the host´s behaviour, habitat use, energetic needs, and have ripple effects on the food web.

Where you surprised by anything when working on it?

When comparing fish that were previously naïve to the parasite versus fish that already had an established infection, we saw that previously exposed hosts had a larger response to infectious parasite stages in terms of both their behaviour and physiology. That is, they potentially learned to fear attacking parasites or otherwise became sensitized to the parasite’s attack following previous experience, in a similar way that prey learn to avoid their main predators.

About the Author

How did you get involved in ecology?

Dr. Lauren Nadler recording fish social behaviours on SCUBA using a 3D stereocamera on the Great Barrier Reef, Australia (photo credit Eva McClure).
Dr. Lauren Nadler recording fish social behaviours on SCUBA using a 3D stereocamera on the Great Barrier Reef, Australia (photo credit Eva McClure).

When I was five years old, my parents took me to a local aquarium in New Jersey, USA, and I was instantly hooked. From then on, my dream was to become a marine biologist. This dream was fostered throughout my education, as I was able to take part in ecological research starting as early as my undergraduate degree at Boston University (USA). While there, I completed diverse projects related to coral restoration and disease dynamics in bats. I then went on to complete my Masters of Research at the University of Glasgow (UK), where I again tried to gain skills as broad as possible, working on projects related to fisheries management in Scotland and coral reef fish ecology in Egypt. This broad research base really helped me to hone my interests and goals. I realized that field work and live animal research was what really excited me, so I went on to complete a PhD at James Cook University in Australia, examining the behavioural and physiological effects of social behaviour in coral reef fish. This background in animal behaviour and physiology helped me to get my postdoc, as I used this skill base to study the effects of parasites on their hosts.

What’s your current position?

I completed the research featured in this paper as part of a postdoctoral fellowship based jointly between the Hechinger Lab at Scripps Institution of Oceanography and the Øverli Group at the Norwegian University of Life Sciences. This past summer, I started a faculty position (at the Assistant Professor level) at Nova Southeastern University in southern Florida, USA.

What is the best thing about being an ecologist?

Dr. Lauren Nadler preparing field study mesocosms at the Kendall-Frost Mission Bay Marsh Reserve in San Diego, California, where the killifish used in this study were collected. (photo credit Stephen Brown).
Dr. Lauren Nadler preparing field study mesocosms at the Kendall-Frost Mission Bay Marsh Reserve in San Diego, California, where the killifish used in this study were collected. (photo credit Stephen Brown).

As an experimental biologist, my job frequently entails thinking outside of the box to devise new and innovative ways to measure an animal’s characteristics in as realistic a setting as possible. Over the years, this has required building a whole range of gadgets and learning tons of skills not typically attributed to ecology. So, I frequently get the opportunity to stretch my creative side to achieve these goals. No two days are ever the same, which keeps me excited to go work on a day to day basis.

Read the paper in full here.