By: Lisa Yeter Mesrop

Hello Everyone — My name is Lisa Yeter Mesrop, and I’m a third-year graduate student in Dr. Todd Oakley’s Lab at the University of California, Santa Barbara. I’m interested in understanding the evolutionary and developmental basis by which organismal complexity increases. More specifically, how do novel cell types originate and come together to form organ-level structures?

My study system is the light organ in bioluminescent ostracods (‘Sea fireflies’). The light organ is absent in closely related, but non-bioluminescent ostracods, and therefore is unique to the bioluminescent lineage and a fascinating system to study origins of novelty.

A bioluminescent ostracod, Vargula tsujii, spitting out packets of glowing mucus. The ‘upper lip’ organ is highlighted by the red circle.

Sea fireflies are tiny crustaceans that produce bioluminescence from their light organ. The light organ has two specialized cell types that separately produce the enzyme and substrate needed for the biochemical light reaction (Huvard, 1993). I want to sequence all the expressed genes of individual cell types during the development of the light organ to characterize the genetic regulatory programs that differentiate the novel cell types.

But in order to perform this type of analysis, I need to collect A LOT of bioluminescent ostracods to have enough cells from each developmental timepoint. A recent study by Goodheart et al. (2020) found that the bioluminescent ostracod, Vargula tsujii, was mainly found in large populations by the Wrigley Pier on Catalina Island. Too good to be true?!

I would make sure to set up my traps early so I can sit on the pier and watch the sunset.

I’m so happy for the opportunity to return to Wrigley this summer to collect bioluminescent ostracods for my research. The Wrigley staff are always welcoming and super helpful in getting me set up in the lab space.

Since bioluminescent ostracods are nocturnal, I have to collect them after sunset when it’s dark out. Every night I pack up my buckets and bait my traps with raw chicken liver (YES, I said chicken liver! Mmmm mmmm) and deploy my traps over the side of the Wrigley pier. About two hours after sunset, I would go back to collect the traps in the dark. Finally, I would bring the traps back to the lab and process them by removing the bait and re-suspending the ostracods in filtered seawater.

Image A: Setting up my traps; Image B: Ready to deploy my traps off the Wrigley pier

Image C: My workstation; Image D; Two female V.tsujii.

This past year has been difficult to perform research due to COVID restrictions, and I was not able to perform any of the wet-lab work I had planned for the academic year. Despite having my graduate plans derailed for an entire year, I carried on because I love my research and the exciting questions I get to explore. Thank you Wrigley for allowing me to do my fieldwork in Catalina island!

This little guy came by my room every morning to say hello!

References:

Huvard AL. Ultrastructure of the light organ and immunocytochemical localization of luciferase
in luminescent marine ostracods (Crustacea: Ostracoda: Cypridinidae). J Morphol. 1993
Nov;218(2):181-193. doi: 10.1002/jmor.1052180207. PMID: 29865469.

Goodheart, J.A., Minsky, G., Brynjegard-Bialik, M.N. et al. Laboratory culture of the California Sea Firefly Vargula tsujii (Ostracoda: Cypridinidae): Developing a model system for the evolution of marine bioluminescence. Sci Rep 10, 10443 (2020). https://doi.org/10.1038/s41598-020-67209-w

By: Darrin Ambat

Hi everyone! My name is Darrin Ambat and I am in my third year as a M.S. student in Dr. Matt Edwards’s Kelp Ecology Lab at San Diego State University (SDSU).

Figure 1. Photograph from diving during acidification trials in Big Fisherman’s Cove, Catalina Island. Forefront: Darrin Ambat, USC Wrigley Fellow. Background: Erin Tharp, USC REU. Photo cred: Brayden Wiley, USC REU.

Throughout my academic career, the impacts of human-induced environmental change have been the guiding topic of my research interests. Specifically, I have been drawn to studying the effects of ocean acidification (OA) on fish reproduction, a vital physiological process for all living organisms. Fish are not only an important economic resource in terms of human consumption, but they also play a critical role in the ecology of marine ecosystems. Thus, my study will provide an innovative solution to examining how human-induced disturbances impact marine ecosystems.

Before getting permission to work at the USC Wrigley Institute of Environmental Studies (WIES) during the pandemic, I spent countless hours diving around San Diego and Long Beach searching for historically known populations of bluebanded gobies. Safe to say, I came up empty-handed and WIES remains the ideal location for my study due to its proximity to my study site and access to dense populations of bluebanded gobies.

Finally, after impatiently waiting, I can remove my mask and exchange it for another, except this time it’s for scuba diving! My USC REU student, Brayden Wiley, and I packed our bags and boarded the Miss Christi to head to Catalina Island and live on the WIES campus for the entire summer field season. We are currently going on week 5 of our 10 week stay and what a rollercoaster it has been. Between designing an entire new laboratory aquarium system to equipment either breaking or not working to begin with, we have managed to get experiments running smoothly!

Figure 2a. Rock covered with bluebanded gobies.

Fig 2b. Bluebanded goby eggs laid in a ‘Tunnel of Love’.

My research focuses on the effects of OA on the reproduction of bluebanded gobies. My primary goal is to develop novel techniques to evaluate how OA affects bluebanded goby reproductive output and behavior under ecologically realistic conditions in both laboratory and field experiments. In the laboratory, I use aquarium tanks to examine bluebanded goby reproduction by examining the quantity of eggs laid in each nest.

Similarly, in the field, I deploy benthic chambers that mimic laboratory tanks but incorporate important variables such as predator and light cues not found in a laboratory setting. Both settings are subjected to one of two experimental conditions: present day (ambient) or future OA (lowered seawater pH/acidified) conditions. Bluebanded gobies readily reproduce in artificial reefs within nesting tubes called Tunnels of Love. Their eggs will then be counted to quantify total reproduction and video recordings will be analyzed to examine adult behavior.

Figure 3. Photograph of benthic chamber deployed in Big Fisherman’s Cove, Catalina Island. Chambers are ready to be acidified while a predator (Kelp Bass) lurks for its next meal.

Our results indicate that the average number of eggs laid in the control treatment is higher than that in the OA treatment. This means that adult bluebanded gobies produce more babies under normal conditions compared to acidified conditions that are projected to occur by the end of this century. However, the average egg size laid in acidified treatments is larger than that of the control treatment. So, does OA cause a problem for fish reproduction? Bluebanded gobies seem to be producing less eggs in acidified treatments, but if they are bigger, they may be more likely to survive. Stay tuned to see where further results lead us!

I have had the opportunity to conduct research at WIES during previous summers as a research intern and even conducted preliminary thesis research, so I was eager to be back as a Wrigley Fellow. Thankfully, we are back conducting research at WIES again.