1.13.T-06 - Assessing Disruption of Metamorphosis From Concurrent Chemical and Environmental Stressors Using Alligator Gar (Atractosteus spatula) as a Model

Abstract

---

Metamorphosis is a vital transformation that is largely controlled by the thyroid axis and plays a role in the survival and population recruitment of most fishes. The thyroid axis can be disrupted by anthropogenic chemicals found in surface waters and environmental changes, such as fluctuating temperatures. Disruption by these stressors can result in accelerated, delayed, or even prevented metamorphosis causing poor recruitment. In the environment, fishes are concurrently exposed to chemicals and environmental changes which could additively disrupt metamorphosis. However, the additivity of stressors on metamorphosis in fishes is poorly understood. Therefore, this study used a previously developed Fish Metamorphosis Toxicity Test to assess the combined impact of temperature and chemical exposure on metamorphic disruption using the alligator gar (Atractosteus spatula) as a model. The alligator gar was chosen to represent fishes with a dramatic metamorphic transformation compared to the common model, zebrafish (Danio rerio), which has a subtle metamorphic transformation. Fishes with a dramatic metamorphic transformation are overlooked in risk assessments, and a previous study showed that the alligator gar was more sensitive to disruption of metamorphosis by triiodothyronine (T3) relative to zebrafish. Here, alligator gar were exposed to sub-lethal concentrations of T3 (0, 0.15, 0.93, and 5.56ppb) at 24C and 28C for the duration of metamorphosis, approximately 5 to 30 days post-hatch. Progression of metamorphic milestones and mortality were recorded. Individuals exposed to 5.56ppb of T3 at 28°C developed jaw deformities, abnormal body proportions, and had the greatest rate of morality at approximately 30%. However, individuals exposed to 5.56ppb T3 at 24 °C developed abnormal body proportions but had no jaw deformities and a mortality rate of approximately 16%. In contrast, individuals exposed to 0.15ppb T3 had a beneficial response, with normal development and an accelerated growth rate relative to controls. Overall, this study demonstrates the additive effect of exposure to greater temperature and T3 on disruption of metamorphosis in a species of fish with a dramatic metamorphic transformation. This research begins to elucidate the risks posed by chemical pollution and environmental change to population recruitment among fishes with dramatic metamorphic transformations, which include numerous species of economic and ecological importance around the world.

Author(s)

---

Presenter: Lauren Eagon, Louisiana State University Baton Rouge,

Authors:
Lauren Eagon Louisiana State University Baton Rouge United States
Vann Boyte Louisiana State University Baton Rouge United States
Cameron Collins Louisiana State University Baton Rouge United States
Jon Doering Louisiana State University United States