o really appreciate the zebra-fish, you have to look closely. Because at first glance, the diminutive member of the minnow family appears to be a perfectly ordinary, if not unremarkable, organism. The adults possess a restrained style, with characteristic horizontal stripes that adorn their small bodies, but the newly hatched aren’t much to look at — literally — because they’re only a few millimeters long and nearly fully transparent. However, under a microscope, the zebrafish emerges as a model organism for biological research, both at Bucknell and throughout the world.

“Students can use model organisms to explore questions ranging from the molecular level, like how individual neurons are built, all the way up to the systems level, like how neural circuits drive specific behaviors,” says Professor Matthew Clark, biology. “There are all these different kinds of model organisms, like mice, zebra-fish and fruit flies, that can be studied to better understand how more complex networks of cells and neurons are working together to perform particular functions.”

Under a microscope, the see-through bodies of larval zebrafish unveil intricate details that help researchers study everything from the movement of the circulatory system to the resolution of individual cells, which can be observed to gain insight about how cells communicate to generate specific behaviors.

To answer questions about whether certain behaviors are intrinsic to zebrafish, Bucknell students also study betta fish to draw comparisons between the two species. Of course, to be able to study these organisms side by side, Capri Mills ’26, a Presidential Fellow and biology major, had to learn the ins and outs of fish husbandry.

“With betta fish, it’s actually really complex,” Mills says, noting that the male and female bettas have to be closely monitored so courtship doesn’t lead to death. “He will essentially wrap his body around her and squeeze her eggs out while fertilizing them as they come out. Then the male will blow a bunch of bubbles called a bubble nest and pick up all of his eggs from the ground and place them in the bubble nest so they float.”

As Mills learned, breeding zebrafish is a bit more straightforward, which is just one of a number of reasons that make them ideal research subjects. They share 70% of their genes with humans, and 84% of the genes responsible for human disease have a genetic counterpart in zebra-fish, meaning that discoveries about these fish might lead to breakthroughs in treatment. They also possess a remarkable capacity for regeneration and can fully recover from a variety of injuries. Though it is the optical clarity of the embryonic and larval fish that really gives scientists a window into their inner workings.

In her work with fish, Mills has gained a deeper interest in the field of neuroscience and a greater appreciation of the precision and scrupulousness required in laboratory research.

“It only makes me admire other people’s work more because of the amount of time and dedication it takes to gather data for an experiment, analyze it and publish a paper,” says Mills. “Being able to perform this work with a team has helped prepare me for what comes next.”