LB 23-243 - Modeling Food Dependent Symbiosis in Exaiptasia pallida

Thursday, August 18, 2022

5:00 PM – 6:30 PM EDT

Located in: ESA Exhibit Hall

Presenting Author(s)

JK

Jakob Kaare-Rasmussen, n/a

Undergraduate Researcher
University of California, Santa Barbara, United States

Coauthor(s)

FP

Ferdinand Pfab, n/a

Postdoctoral Scholar
University of California, Santa Barbara, United States
HM

Holly V. Moeller, n/a

Principal Investigator
University of California, Santa Barbara, United States

Background/Question/Methods:

The delicate mutualism between Cnidarians and their symbionts is rooted in nutrient sharing. Cnidarian hosts provide their symbionts with a variety of nutrients including nitrogen while symbionts can photosynthesize, providing the host with carbohydrates. Symbionts can either be costly or beneficial to the host, depending on the food available to the host. Previously published work by Peng et al. 2020 studied the food-dependent nature of the mutualism of Exaiptasia pallida and their symbionts. This study showed a surprising amplification effect of symbionts on anemone performance. While well-fed anemones grow faster with symbionts than without them, starved anemones suffer from malnourishment and die much faster when they are inoculated with symbionts. Yet, it is still unclear how nutrients travel from the host to their symbionts. Here, we use a Dynamic Energy Budget (DEB) model to quantify the impact of food availability on the mutualism between the anemone host and symbionts in this system with a focus on capturing the amplifying effect of the symbiont. We sought to test if this exchange of nutrients can be approximated as the symbiont actively consuming ("eating") the host.

Results/Conclusions:

This model accurately captures the amplifying effect symbionts have on anemones and quantifies the food availability that anemones need to maintain mutualism with their symbionts. We found that the approximation of the symbiont actively consuming ("eating") the host improved model fits by accurately capturing the transient benefits the symbionts can accrue even as the anemone host has begun to decline.. Using the data-validated model, we are then able to predict threshold levels of food and light availability that drive transitions between a healthy mutualism and dysbiosis. This model furthers our understanding of how other biological traits, like the photosynthesis rate of the symbionts, impact the delicate mutualism balance. Lastly, since E. pallida are model organisms for other Cnidarians, this model helps us better understand the cost-benefit balance in coral mutualism.