BRC-BIO: Effects of insecticides on survival and metamorphosis of the upside-down jellyfish, Cassiopea xamachana, and its symbiotic community

Coral reefs are of tremendous ecological importance and also provide economic and social value through coastal protection, tourism, and as a source of food and pharmaceuticals. Further, they are complex organisms that have a diverse bacterial community living on and in their cells (comprising a holobiont, the organism and its symbionts). However, there are significant limitations to the study of these holobionts.

In this project, the closely-related upside-down jellyfish (Cassiopea xamachana) is developed as a model for understanding environmental effects on nearshore corals. These jellyfish contain a similar but less complex bacterial community, are abundant, uncomplicated to collect, and easy to study under laboratory conditions. Using insecticide exposure (associated with mosquito control) as a common near shore stressor, the project will quantify the effects of exposure on survival and changes in growth of all members of the holobiont, as well as changes in the function and interactions of the jellyfish bacterial microbiome.

In addition to the potential to learn more about processes that will affect the coral community in the Florida Keys, this project will allow more undergraduate students to access scientific research and the field of biology, giving them an opportunity to consider research-based careers. By expanding undergraduate research at an institution with a high proportion of first-generation students and students of color, the voices involved in biology research can be broadened, while also bringing new ways of thinking and approaching problems to the scientific community.

The overarching theme of this project is to advance the C. xamachana photosymbiotic holobiont as an experimental system for studies on cnidarian associated individual microbes, the photosymbiont, and the polyp holobiont as well as the impact of insecticide exposure on these systems. The diverse cnidarian holobiont with its complex life cycle offers many potential targets also allows for the diverse ways insecticides that reach coastal waters.

However, little work has been done to investigate the effects of insecticide exposure on coral survival, nor on the photosymbiotic Symbiodiniaceae or bacterial/archaeal microbiome which are integral to cnidarian health. C. xamachana is the ideal system to begin to discriminate the roles each microbial member plays in the response of a photosymbiotic cnidarian life cycle to insecticide exposure.

C. xamachana exhibits an asexual polyp life stage that is only terminated after the establishment of photosymbiosis, an event accompanied by a distinct developmental transition from sessile polyp to juvenile medusa. Changes in bacterial gene expression in response to insecticide exposure during that developmental transition will be interrogated using next-generation sequencing.

High-resolution microscopy and fluorescence in situ hybridization will localize bacteria of interest in the jellyfish. By combining these approaches with an examination of polyp nerve net function and growth of individual Symbiodiniaceae and bacterial cultures we can understand how exposure to the three insecticides used for mosquito control in the Florida Keys affects the diverse cnidarian holobiont.

These results can inform conservation decisions on the Florida reef tract, threatened by a severe disease outbreak that may more strongly impact stressed corals, such as those exposed to insecticides.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.