Persistent Effects of Larval Exposure to Glyphosate in Mangrove Rivulus Fish

Date of Award

5-5-2024

Degree Name

M.S. in Biology

Department

Department of Biology

Advisor/Chair

Karolyn Hansen

Abstract

Glyphosate, a key ingredient in roundup, is increasingly present in aquatic systems due to agricultural runoff. High doses of this toxin cause defect in organisms due to its ability to interfere with physiological processes as an endocrine disruptor. I used the mangrove rivulus fish (Kryptolebias marmoratus) to evaluate the effects of glyphosate on non-target species in aquatic environments. They are self-fertilizing amphibious hermaphrodites with the ability to escape water in times of poor quality, predation, and nesting. These fish produce genetically identical offspring, allowing us to evaluate how variation in toxicant exposure alters their phenotypes while ruling out genetic effects. I treated newly hatched larvae for 96 hours with three different concentrations of glyphosate: control (0mg/L), environmentally relevant (.01 mg/L), and high (1 mg/L), and then measured behavior, morphology, and reproductive traits at 60 and 130 days. I predicted that fish exposed to low, environmentally relevant doses would show adaptive jumping behavior, and deficits in other traits would be greater with higher glyphosate dosages. I found phenotypic changes in reproductive output, behavior, and jumping ability; none of these effects appeared to be adaptive at low or high doses of glyphosate. Deficits in reproductive output scaled with dosage while other phenotypic deficits largely did not scale with treatment; instead, they were treatment specific for each trait. For instance, I found that low doses of glyphosate led to lower anxiety (decreased thigmotaxis), impaired jumping behaviors, and hormonal imbalances while high dose exposures to glyphosate resulted in impaired anti-predator behavior and lower average egg yield per individual. This study displayed the importance of maintaining healthy ecosystems by showing even environmentally relevant concentrations of herbicide may be harmful to aquatic organisms and have lifelong consequences. Furthermore, implications of environmentally relevant concentrations of glyphosate in the wild can have negative effects such as deficits in reproductive output which further have population level consequences.

Keywords

Glyphosate, Roundup, Fish Behavior, Endocrine Disruption

Rights Statement

Copyright 2024, author

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