I am a reproductive endocrinologist primarily interested in the mechanisms by which environmental factors influence the reproduction and development of aquatic animals. Specifically, my interests tend to center around three main research areas:
1) The influence of endocrine disrupting contaminants in reproductive and developmental dysfunction.
2) Reproductive and developmental challenges in commercial aquaculture.
3) Methods to reduce contaminant burdens in aquaculture species.
A vast literature now exists linking environmental contaminants with a variety of reproductive and developmental dysfunctions in wildlife. In addition to ubiquitous aquatic pollutants (PCBs, legacy pesticides, plasticizers, etc.), fish in aquaculture environments are exposed further still to a variety of chemicals associated with PVC piping, handling equipment, therapeutic pesticides, resins, plastics and others. In addition, fish held in recirculating systems are often exposed to elevated concentrations of nitrate, which has not been considered a material water quality hazard in aquaculture, despite the growing number of studies describing nitrate’s ability to cause a host of reproductive dysfunctions.
Research examining the impacts of environmental contaminants on wildlife is experiencing a paradigm shift driven by several important discoveries: the significance of fetal exposures to adult reproductive dysfunction, the understanding that many environmental exposures have non-linear dose-response curves, and that lower, often environmentally relevant concentrations of pollutants, can cause more harmful effects than more elevated concentrations. The previous dogma that ‘the dose makes the poison’, no longer holds true in studies of endocrine disruption, and understanding the effects of environmentally relevant, low dose exposures and the etiology that drives them is a pivotal aspect of my research. My students and I use both hormonal and molecular endpoints to address these questions in several finfish models including sturgeon, killifish and bamboo sharks.
1. Moore, B.C., Roark, A., Kohno, S, Hamlin, H.J., Guillette, L.J. 2012. Gene-environment interactions: Potential role of contaminants on somatic growth and the development of the reproductive system of the American alligator. Molecular and Cellular Endocrinology, in press.
2. Moore, B.C., Forouhar, S., Kohno, S., Botteri, N, Hamlin, H.J., Guillette, L.J. 2012. Gonadotropin-induced changes in oviducal mRNA expression levels of sex steroid hormone receptors and activin-related signaling factors in the alligator. General and Comparative Endocrinology 175, 251-258.
3. Boggs, A.S.P., Hamlin, H.J., Lowers, R.H., Guillette, L.J., Jr. 2011. Seasonal variation in plasma thyroid hormone concentrations in coastal versus inland populations of juvenile American alligators (Alligator mississippiensis): influence of dietary iodide. General and Comparative Endocrinology 174, 362-369.
4. Hamlin, H.J., Lowers, R., Guillette, L.J., Jr. 2011. Seasonal androgen cycles in adult male alligators (Alligator mississippiensis) from a barrier island population. Biology of Reproduction 85, 1108-1113.
5. Morris, A.L., Hamlin, H.J., Floyd, R.F., Sheppard, B.J., Guillette, L.J., Jr., 2011. Nitrate induced hypothyroidism in white-spotted bamboo sharks (Chiloscyllium plagiosum). Journal of Aquatic Animal Health 23, 92-99.