Story posted April 12, 2013
Continuing a project previously researched by Tamara Perreault ‘12 and Julia Livermore ‘13, Christine Rholl ’14—one of this year’s Doherty fellows—hopes to better understand bioluminescent scale worms (Harmathoe imbricata) by testing their methods of survivorship against lobsters
These particular scale worms are known for their reaction to predation. When in the presence of lobsters, the scale worms "will either flash, so their entire body will light up," Rholl explains, "or they will autotomize their scales and their tail and only their scales will light up.and float around."
This bioluminescent display, and the particular randomness of the worm's autotomized floating scales, creates a decoy for the lobsters, oftentimes allowing the scale worms to escape unscathed.
Rholl’s research is comprised of trying to better understand the survivorship of these bioluminescent scale worms by replicating their light displays in the presence of both blinded and unblinded lobsters to see if there are different reactions.
"Nocturnal predators" by natural design, the lobsters must be in completely dark conditions in order to evaluate the scale worm's survivorship and the effectiveness of their natural decoy when they self-autotomize.
When blinded, the lobsters seem more likely to successfully prey on the scale worms. Without the natural light display of their autotomized scales, the lobsters are able to follow the chemical cues of the scale worms without being distracted.
In conducting this experiment and researching her findings, Rholl has not had an easy time.
"We can't have any extra light in the tank with the lobsters" Rholl explains, "they're nocturnal predators so they're in complete darkness."
Rholl’s biggest challenge so far has been replicating the exact darkness of a feeding lobster's natural environment while replicating the light display of the bioluminescent scale worms.
First, in order to replicate the bioluminescent display, Rholl has programmed an LED light to display in a similar manner to the natural bioluminescence of the scale worms when their scales autotomize.
Next, these lights will be introduced to the tanks containing both blinded and unblinded lobsters to see whether the lobsters will be more successful at capturing their prey.
According to Livermore’s '13 research, the lobsters will be more successful at catching the scale worms when blinded because they will be responding instinctually, rather than being deterred by the natural decoy of the autotomized scales.
For this to be experimented, Christine explains, there needs to be no extra light in the tank with the lobsters.
"We found out that the backlight is not controllable." While her LED has been able to replicate the bioluminescent light display, the trials will not be valid if the backlight is present, as the lobsters will be able to see the prey.
Another hurdle Rholl has had to face while conducting her research is discrepancies between her findings and the findings of her predecessors. Livermore found that blinded lobsters were more often able to successfully kill their prey, whereas the unblinded lobsters would go after the decoy scales.
"So far, I haven't seen quite the same trends," Rholl explains, "she didn't have quite enough trials. The whole goal for me to start my project was to finish up enough trials to make her sample size big enough to make it statistically significant."
While there is still much to work through, Rholl’s research is on its way to offering a better understanding of the largely unknown behavior of bioluminescent marine life and the way their displays hinder or allow their survivorship.