R. David Maclaren
- Animal Behavior
- Comparative Animal Anatomy & Physiology I: Nervous & Endocrine Systems
- Marine Biology & Sustainability
- Principles of Biology II Lecture & Labs
- Directed Study/Research I and II
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.
Experiments with A. nigrofasciata my students and I (in collaboration with Dr. Stephan Theberge in Merrimack’s Dept. of Chemistry & Biochemistry) are working on in connection with this project include the following:
1. Effects of acute exposure to atrazine and fluoxetine on intraspecific aggression.
2. Effects of long-term exposure to atrazine and fluoxetine on intraspecific aggression.
3. Effects of acute atrazine and fluoxetine exposure on female mate choice & fecundity (i.e. # of eggs laid per clutch).
4. Effects of chronic atrazine and fluoxetine exposure on female mate choice &fecundity.
5. Effects of atrazine and fluoxetine on 11-ketotestosterone and cortisol (a stress hormone) levels.
Behavior, ecology, and conservation of marine mammals in the Gulf of Maine: I also hold a strong interest in marine mammal behavior, ecology, and conservation. In Spring 2009 I established a partnership in research and education with the Blue Ocean Society for Marine Conservation (http://www.blueoceansociety.org/), a non-profit organization dedicated to marine mammal research, conservation, and education centered in Portsmouth, NH. During the summer months I serve as “Naturalist” aboard whale watch vessels, collecting behavioral and physical data on the whale, dolphin, and sea bird populations in the Jeffreys Ledge region of the Gulf of Maine while educating the public on marine mammal ecology and conservation. This work involves mentoring undergraduate students conducting summer research at Merrimack and/or interning with Blue Ocean. All the data collected are added to Blue Ocean’s data base, which we then analyze during the off season. As part of this collaboration, Blue Ocean provides competitive internship/research opportunities to Merrimack students interested in marine mammal ecology, behavior & conservation. Click on the following link to view a gallery of pictures taken over the past few seasons on the water:http://merrimack.smugmug.com/Experiential-Learning/Whale-Watch/31065570_SXVLCr#!i=2687311517&k=x5SKjFr
My students and I are currently working on two research projects:
1. The convict cichlid project described above.
2. A collaboration with Blue Ocean scientists in the analysis of 15+ years of marine mammal data from the Jeffreys Ledge region of the Gulf of Maine. Data mining efforts cover a wide range of study questions primarily addressing humpback (Megaptera novaeangliae) and fin whale (Balenoptera physalus) behavior, ecology and conservation.
* denotes undergraduate researcher
MacLaren, R.D. and *Fontaine, A. 2012. Incongruence between the sexes in preferences for body and dorsal fin size in Xiphophorus variatus. Behavioural Processes. DOI: 10.1016/j.beproc.2012.10.013
MacLaren, R.D., Schulte, D. and Kennedy, J. 2012. Field research studying whales in an undergraduate animal behavior laboratory. Bioscene Journal of College Biology Teaching.
MacLaren, R.D. and *Fontaine, A. 2012. Female bias for male lateral projection area in Poecilia reticulata. Environmental Biology of Fishes. Vol. 93, Issue 1, 105-119.
MacLaren, R.D., *He, R., and *Gagnon, J. 2011. Bias for enlarged male body and dorsal fins in female Xiphophorus variatus. Behavioural Processes 87, 197-202.
MacLaren, R.D. and *Daniska, D. 2008. Female preferences for dorsal fin and body size in Xiphophorus helleri : further investigation of the LPA bias in Poeciliid fishes. Behaviour. 145, 897-913.
MacLaren, R.D. 2007. Female preference in Xiphophorus helleri: Further investigation of the LPA bias in Poeciliid fishes. 2007 Annual Animal Behavior Society Conference Abstracts.
MacLaren, R.D. 2006. The effects of male proximity, apparent size, and absolute size on female preference in the sailfin molly, Poecilia latipinna. Behaviour. 143, 1457-1472
MacLaren, R.D. and Rowland, W.J. 2006a. Female preference for male lateral projection area in the shortfin molly Poecilia mexicana; evidence for a preexisting bias. Ethology. 112, 678-690.
MacLaren, R.D. and Rowland, W.J. 2006b. Differences in female preferences for male body size in Poecilia latipinna using simultaneous vs. sequential stimulus presentation designs. Behaviour. 143, 273-292.
MacLaren, R.D., Rowland, W.J., and *Morgan, N. 2004. Female preferences for sailfin and body size in the sailfin molly,Poecilia latipinna. Ethology.110, 363-379.
Rowland, W.J., *Grindle, N., MacLaren, R.D., and Granquist, R.2002. Male preference for a subtle posture cue that signals spawning readiness in female sticklebacks. Animal Behaviour. 63.
Supplemental figures 4 & 5 accompanying “Field research studying whales in an undergraduate animal behavior laboratory” by MacLaren, R.D., Schulte, D. and Kennedy, J. Published in Bioscene Journal of College Biology Teaching in spring 2012.