By: Jason Wang
Hello, my name is Jason Wang and I’ve just finished my second year as a PhD student at USC working with Dr. Donal Manahan. I’m excited and thankful for the opportunity to continue my research activities this summer as a graduate fellow supported by the Wrigley Institute! I am primarily interested in asking the question of how it is that marine animals survive, cope with, or thrive in the environments they are found in. This question takes me down many roads branching from the study of their physiology to cellular biology & biochemistry, all the way down to their genes & DNA.
The large-scale larval culturing facility at Wrigley Marine Science Center. Each tank holds 200 liters of pristine seawater pumped from the waters around Catalina Island, and houses 2 million oyster larvae.
Why does this matter? Well other than being just plain interesting to me, the research I’ll be doing has implications for how marine organisms may fare in changing oceans, how seafood is produced to sustain a growing population, the cycling of organic matter in the water column, and finally improving our understanding of basic biological processes common to all animal life.
Left: A female white urchin releases 400,000 eggs to be fertilized for culturing. Middle: Purple urchin larvae after one week of development have apparent digestive systems full of algal food. Right: Several purple urchins spawning
This summer I will be using the white urchin Lytechinus pictus and the Pacific oyster Crassostrea gigas as model organisms for studying how larval growth rates are influenced by the physiology of feeding. One of the first observations many people make when seeing an urchin larva for the first time is how its body resembles a space ship. Most marine invertebrates have a larval form built for dispersal that is distinct from its adult form, and this concept makes the analogy of a space ship very fitting. Much like how a space ship must contain all of the oxygen, food, and fuel/energy to sustain a crew, a marine larva is endowed by its mother with an energetic substrate reserve of lipids, proteins, carbohydrates, as well as the cellular machinery required to fuel its development and eventual settlement in a foreign environment.
Left: Different algal food concentrations fed to urchin larvae to test food conversion efficiencies. Right: Measuring rates of oxygen consumption of hundreds of larvae in a sealed container allows us to calculate how much energy (ATP equivalents) larvae are spending
Where the analogy breaks down (with our current space travel technology), is that eventually the larva will run out of its embryonic resources, and any chance of survival to metamorphosis must be fueled by feeding on an outside source of energy. There are many “strategies” that help larvae to overcome these limitations. For example, the larvae of some species may require less energy to perform essential cellular processes like synthesizing proteins or transporting ions. On the other hand, other species may have more effective means of acquiring food or nutrients. Regardless of the strategies, larvae have but one goal – to develop to a stage where they are competent to settle down in a favorable environment.
Replicate cultures of white urchin larvae held at two constant temperatures. Each container has 140,000 larvae
As you can imagine, there’s only so much that the larva’s biology can contribute to its success. The environment plays a huge role in influencing a larva’s ability to adapt or thrive. However, not all larvae are equal, and it is the goal of my research to study what it is about certain aspects of larval physiology that allow them to thrive and grow quickly in otherwise stressful conditions.
Left: Feeding assay cup containing 10,000 larvae and a known amount of algal food. Right: Hundreds of replicate feeding assay cups allow for precise measurements of ingestion rates used to determine food conversion efficiencies
This summer I have set up several cultures of white urchin and pacific oyster larvae. Each culture can contain hundreds of thousands to millions of larvae such that there is ample biomass to make a multitude of measurements on a common pool of animals. My larval cultures are exposed to various food concentrations, temperatures, and levels of CO2, and I will be tracking the total energy available to them (through respiration), how much protein, lipid, and carbohydrate they consume and deposit as biomass, and finally how quickly they synthesize and turn over the proteins in their bodies. All of these measurements reflect some aspect of energy acquisition, recycling, or utilization and provide indices of growth efficiency.
My hope is to provide quantitative values to describe how larval development is affected by future climate scenarios. It’s not enough to just say that climate change is affecting marine life – I want to know specifically by how much and in what way life is affected; but more importantly, what might the “winners” in future oceans look like and how can we use that information to maximize the way we grow food in the oceans?