Research

Ecological and Comparative Physiology

Our research focuses on the physiological adaptations of marine and freshwater organisms to naturally-occurring environmental stressors, such as hypoxia, hydrogen sulfide, temperature and caloric restriction, and the effects of contaminants on these adaptations. We utilize a wide variety of techniques (ranging from biophysics, biochemistry and molecular biology, to whole-animal metabolic measurements and field studies) to understand these adaptations among many animals and habitats. We focus primarily on marine invertebrates, but we also use “model” systems, such as C. elegans, yeast and mammalian cell cultures, when we think those systems will help us get closer to the answers.

Multiple-stressor Interactions

Animals in most natural habitats are exposed to a range of potentially stressful conditions, termed environmental stressors. Traditionally, studies investigating animals’ physiological and molecular responses to environmental stressors have used a single-stressor approach in a controlled laboratory setting, but in natural habitats stressors frequently occur in combination. Simultaneous exposure to multiple stressors may produce interactions, resulting in physiological responses that are significantly different from responses observed during single stressor exposure. Understanding how multiple stressors interact is essential to predicting the impact of stressors on species survival, biodiversity, community dynamics and ranges.

We have been investigating multiple stressor interactions in two organisms, the nematode C. elegans and the horseshoe crab Limulus polyphemus. Each of these animals provides specific advantages. In the figure at right (from J. Exp. Biol. 218:2355-2364, 2015), we show a Hutchinsonian niche space model that depicts the conditions at which horseshoe crab eggs are able to develop during exposure to ranges of oxygen, temperature and salinity.

Adaptations of Marine Invertebrates to Hydrogen Sulfide and Free Radicals

In previous studies, we were particularly interested in physiological adaptations of marine animals to the metabolic poison hydrogen sulfide. This gas (and weak acid) is a natural byproduct of bacterial reduction in environments that are both high in nutrients and low in oxygen. These two conditions commonly coexist in the sediments of mudflats, estuaries, rivers and lakes. Hydrogen sulfide is also present at high concentrations at certain locations on the sea floor, such as at hydrothermal vents and cold seeps.

Prior Research

Much of our prior work focused on the polychaete bloodworm Glycera dibranchiata, the hard clam Mercenaria mercenaria, deep sea tubeworms, and the coastal echiuran worm Urechis caupo.