The Plasticity of Social Status: Stress Hormones in a Hermaphroditic Fish
Additional Funding Sources
The project describe was supported by the Department of Biological Sciences startup funds to DSP of and Strategic Initiative Undergraduate Award to MS of Idaho State University.
Abstract
Psychosocial stress due to dominance rank can have profound effects on physiology, behavior, and metabolism. Cortisol, a hormone that controls stress-induced responses in all vertebrates, may be an important mediator of changes in behavioral phenotype due to social structure or changes in status, such as dominance and/or subordinate rank. Bluebanded gobies, Lythrypnus dalli, are bidirectionally hermaphroditic fish, in which sex change occurs due to a change in social structure. In stable groups, L. dalli live in linear social dominance hierarchies, such that one male dominates over many females and defends a nesting territory. Upon male removal (MR), the most dominant female exhibits rapid increases in rates of aggressive and territorial behavior. This species is ideal for exploring the effect of social status and instability on cortisol levels due to the plasticity of life history transitions, such as sex change. Here, we compared systemic cortisol levels amongst the group hierarchy in stable groups, 30 min after MR, and 24 h after MR. Behavioral observations were taken in 10 min bins and used to determine the status of each fish in a group. There was no significant difference in water-borne cortisol level in stable groups or after male removal. These data indicate that systemic cortisol levels are not associated with psychosocial stress. Future studies will investigate more specific measures from brain, such as cortisol, cortisol producing enzymes, or glucocorticoid receptor levels.
The Plasticity of Social Status: Stress Hormones in a Hermaphroditic Fish
Psychosocial stress due to dominance rank can have profound effects on physiology, behavior, and metabolism. Cortisol, a hormone that controls stress-induced responses in all vertebrates, may be an important mediator of changes in behavioral phenotype due to social structure or changes in status, such as dominance and/or subordinate rank. Bluebanded gobies, Lythrypnus dalli, are bidirectionally hermaphroditic fish, in which sex change occurs due to a change in social structure. In stable groups, L. dalli live in linear social dominance hierarchies, such that one male dominates over many females and defends a nesting territory. Upon male removal (MR), the most dominant female exhibits rapid increases in rates of aggressive and territorial behavior. This species is ideal for exploring the effect of social status and instability on cortisol levels due to the plasticity of life history transitions, such as sex change. Here, we compared systemic cortisol levels amongst the group hierarchy in stable groups, 30 min after MR, and 24 h after MR. Behavioral observations were taken in 10 min bins and used to determine the status of each fish in a group. There was no significant difference in water-borne cortisol level in stable groups or after male removal. These data indicate that systemic cortisol levels are not associated with psychosocial stress. Future studies will investigate more specific measures from brain, such as cortisol, cortisol producing enzymes, or glucocorticoid receptor levels.