UCSB graduate student shines light on sea creatures’ reproductions
As a boy, Nicholai Hensley wanted an unusual pet.
“I didn’t want a dog. I wanted an octopus,” the 28-year-old UCSB graduate student told the News-Press as his adviser, Dr. Todd Oakley, listened in the latter’s office. “But my parents said, ‘That’s way too hard to take care of.’ “
Instead of a pet octopus, the Santa Barbara resident grew up to get something more dramatic: a chance to study tiny crustaceans and how they project brilliant light to attract female mates or repel predatory fish.
The crustaceans, which are the size of a sesame seed, are called ostracods, and scientists have known about their blue-green light since the 1980s. But in his nearly six years of research, Mr. Hensley discovered new details about the light, and his paper on them was recently published in Proceedings B, the journal of the London-based Royal Society.
“He established that biochemistry matters for courtship signals,” Dr. Oakley, 48, said.
Mr. Hensley, a Santa Ana native and 2008 graduate from Cardinal Newman High School in Santa Rosa, earned his bachelor’s in ecology, behavior and evolution in 2012 at UCLA.
He’s working to earn his doctorate in the same field in 2020 at UCSB.
“I didn’t know ostracods existed until I came to graduate school,” Mr. Hensley said.”I wasn’t sure what I wanted to work on, but I knew I really liked animal behavior and the genetic component that might contribute to animal behavior,” he added.
Dr. Oakley told Mr. Hensley about the study of ostracods, and the graduate student went to Belize to meet with collaborators during the winter of 2013-2014. There he witnessed the tiny creatures’ dazzling light show.”It was amazing to see these strings of bioluminescent light,” said Mr. Hensley, who worked with a lab mate at UCSB and researchers in Los Angeles, Wisconsin and Kansas.
He and his collaborators continued their trips to the Caribbean to dive in the water and study 16 species of ostracods, who live 100 feet or less beneath the surface.
In addition to Belize, Mr. Hensley said they shot videos and collected data from the waters off Jamaica; Roat n, an island in Honduras; Panama; and Florida.
Dr. Oakley explained the Caribbean ostracods create the light as they expel glowing mucus.
The mucus is injected with an enzyme and a reactant. The ostracod leaves the brilliant orb and swims away to create another one.
The crustacean continues to make one orb after another, resulting in a trail of lights.
“Females will follow along these little dots, which are kind of like an airplane runway,” Mr. Hensley said.
The light is created because a protein interacts with vargulin, a substance present in luminescent organisms, Mr. Hensley said.
The duration of the light varies from a fraction of a second to 10 seconds, depending on the species.
Mr. Hensley said his paper was intended to investigate how the different proteins among the ostracod species affect the light’s duration.
“The conclusion we found was the really surprising part to me,” he said “We thought if a species has a protein that works really efficiently and makes light really fast, you’d expect species with really short pulses.
“What we found is that’s only true for some species but not all species,” Mr. Hensley said.
He said the ostracods might make their light pulses short or fast by using a greater or lesser amount of the protein.
A good question is whether the duration of light matters to the females and why, Mr. Hensley said. “We don’t actually know yet.
“One thing we think might be happening is the females of the species might prefer different pulses (emitted by the males in a courtship),” he said. “Maybe a female in one species is attracted to a really short one.
“My next paper will be on whether these differences in how long the lights are visible matter to the females,” said Mr. Hensley, who’s working on the remaining chapters of his thesis.
The graduate student said Earth’s oceans rival outer space as a frontier with questions waiting to be answered.
“There’s so much of the ocean that’s unexplored. There are always things to find out in the ocean on our own planet.”