R. David Maclaren, Merrimack College
Associate Professor
North Andover, Massachusetts
maclarenr@merrimack.edu
Office:
(978) 837-3543
Expert In
Bio/Research
I have three research foci:
1) The role of sexual selection in fish evolution; 2) Investigating the effects of environmentally realistic herbicide and pharmaceutical exposure on hormone concentrations, reproductive and aggressive behavior in fish; and 2) Behavior, ecology, and conservat...
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1) The role of sexual selection in fish evolution; 2) Investigating the effects of environmentally realistic herbicide and pharmaceutical exposure on hormone concentrations, reproductive and aggressive behavior in fish; and 2) Behavior, ecology, and conservat...
Click to Expand >>
Bio/Research
I have three research foci:
1) The role of sexual selection in fish evolution; 2) Investigating the effects of environmentally realistic herbicide and pharmaceutical exposure on hormone concentrations, reproductive and aggressive behavior in fish; and 2) Behavior, ecology, and conservation of marine mammals in the Gulf of Maine.
Sexual selection in fish evolution: My research combines ethological, evolutionary, ecological, and phylogenetic approaches to investigate animal behavior. Using experimental and observational methods, my interests focus on the elicitation, control, function, and evolution of behavior in fishes. Recent projects investigate visual signals and the mechanisms by which they control and mediate courtship, aggression, and other social behaviors. Much of my research to date involves experimental studies on mate choice, sexual selection and aggression in Poeciliid fishes.
Investigating the effects of environmentally realistic herbicide and pharmaceutical exposure on hormone concentrations, reproductive and aggressive behavior in fish: This project examines the hormonal and behavioral effects of two compounds (fluoxetine and atrazine) on the convict cichlid, Amatitlania nigrofasciata. Atrazine, a widely used herbicide, is the second most commonly used pesticide in the US and is resistant to degradation. Many animal species that spend all or part of their life cycle in water can be exposed to significant levels of the chemical for a considerable part of their life. Non-target species inhabiting water bodies around agricultural fields are particularly at risk for exposure to atrazine. Atrazine induces aromatization of testosterone to estradiol, thereby causing an estrogenic effect in exposed individuals. Several studies have demonstrated the feminizing effects of atrazine in amphibians, yet the number of studies with ambiguous and conflicting results contributes to preventing policy changes regarding the use of this pesticide.
While the effects of estrogen mimics and endocrine disrupting chemicals have been the focus of numerous studies, the potential risks of exposure to non-steroid pharmaceuticals by comparison are poorly understood. Antidepressant pharmaceuticals such fluoxetine, the active ingredient in Prozac, have been found in wastewater effluent at biologically relevant levels and bioconcentrate in fish. The presence of this type of drug in waterways has the potential to generate potent endocrine-disrupting effects, yet their role in disrupting hormones and behavior has received relatively little attention. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) that is used to treat depression and anxiety disorders in humans. SSRIs act by preventing the reuptake of serotonin from the synaptic cleft, which results in higher extracellular serotonin levels.
Exposure to such chemicals generates changes in behavior. Behavior is therefore an excellent indicator of environmental impacts on an organism as behavioral changes that interfere with a species’ health and sustainability in the environment may be observed long before physiological changes occur. For example, fluoxetine administration has been found to dramatically impact aggression levels in male fish, which has long-term implications for species survival if the ability to reproduce is linked to the ability to defend and maintain a territory as is the case for A. nigrofasciata. Understanding not only individual, but the population level effects of EDC-altered reproductive and aggressive behavior is important to conservation biology. Many contaminants are persistent and remain in the environment at substantial concentrations for several years, spanning multiple generations of short-lived species. Multi-generational disruption of traits used for reproduction such as territorial aggression and mate choice can alter evolutionary trajectories and threaten the species continued existence in the polluted environment.
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1) The role of sexual selection in fish evolution; 2) Investigating the effects of environmentally realistic herbicide and pharmaceutical exposure on hormone concentrations, reproductive and aggressive behavior in fish; and 2) Behavior, ecology, and conservation of marine mammals in the Gulf of Maine.
Sexual selection in fish evolution: My research combines ethological, evolutionary, ecological, and phylogenetic approaches to investigate animal behavior. Using experimental and observational methods, my interests focus on the elicitation, control, function, and evolution of behavior in fishes. Recent projects investigate visual signals and the mechanisms by which they control and mediate courtship, aggression, and other social behaviors. Much of my research to date involves experimental studies on mate choice, sexual selection and aggression in Poeciliid fishes.
Investigating the effects of environmentally realistic herbicide and pharmaceutical exposure on hormone concentrations, reproductive and aggressive behavior in fish: This project examines the hormonal and behavioral effects of two compounds (fluoxetine and atrazine) on the convict cichlid, Amatitlania nigrofasciata. Atrazine, a widely used herbicide, is the second most commonly used pesticide in the US and is resistant to degradation. Many animal species that spend all or part of their life cycle in water can be exposed to significant levels of the chemical for a considerable part of their life. Non-target species inhabiting water bodies around agricultural fields are particularly at risk for exposure to atrazine. Atrazine induces aromatization of testosterone to estradiol, thereby causing an estrogenic effect in exposed individuals. Several studies have demonstrated the feminizing effects of atrazine in amphibians, yet the number of studies with ambiguous and conflicting results contributes to preventing policy changes regarding the use of this pesticide.
While the effects of estrogen mimics and endocrine disrupting chemicals have been the focus of numerous studies, the potential risks of exposure to non-steroid pharmaceuticals by comparison are poorly understood. Antidepressant pharmaceuticals such fluoxetine, the active ingredient in Prozac, have been found in wastewater effluent at biologically relevant levels and bioconcentrate in fish. The presence of this type of drug in waterways has the potential to generate potent endocrine-disrupting effects, yet their role in disrupting hormones and behavior has received relatively little attention. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) that is used to treat depression and anxiety disorders in humans. SSRIs act by preventing the reuptake of serotonin from the synaptic cleft, which results in higher extracellular serotonin levels.
Exposure to such chemicals generates changes in behavior. Behavior is therefore an excellent indicator of environmental impacts on an organism as behavioral changes that interfere with a species’ health and sustainability in the environment may be observed long before physiological changes occur. For example, fluoxetine administration has been found to dramatically impact aggression levels in male fish, which has long-term implications for species survival if the ability to reproduce is linked to the ability to defend and maintain a territory as is the case for A. nigrofasciata. Understanding not only individual, but the population level effects of EDC-altered reproductive and aggressive behavior is important to conservation biology. Many contaminants are persistent and remain in the environment at substantial concentrations for several years, spanning multiple generations of short-lived species. Multi-generational disruption of traits used for reproduction such as territorial aggression and mate choice can alter evolutionary trajectories and threaten the species continued existence in the polluted environment.
Click to Shrink <<