North Atlantic Right Whale Biopsies: Clues to Genetic Response to the Environment

by Judith E. McDowell, WHOI Sea Grant

The North American right whale (Eubalaena glacialis) is one of the most endangered whale species in the world. Once heavily exploited by whalers, right whales now number roughly 350. While no longer fished, the whales remain threatened by other human interactions, such as entanglement in fishing gear and collisions with ships. Another threat, not easily detected, is the uptake and accumulation of persistent organic pollutants (POPs) and the effects these contaminants have on the physiology of the North Atlantic right whale, especially on reproductive biology. In comparison with its South Atlantic counterpart, the North Atlantic right whale has lower calving rates and reproductive rates. Could contaminant exposure contribute to this decline in reproduction?

Many of the persistent contaminants in the marine environment, such as PCBs (polychlorinated biphenyls), dioxins and PAHs (polycyclic aromatic hydrocarbons) are fat-soluble and come to reside in the fatty tissues of marine mammals, including the North Atlantic right whale. Some of these chemicals have been characterized as endocrine disrupters; some are believed to reduce reproductive success, to interfere with developmental processes, and/or to suppress immune function. While PAHs do not bioaccumulate in marine mammals, they may have adverse impacts on the health of animals through repeated exposure and metabolic response.

Joy Lapseritis with a crossbow, preparing to take a biopsy sample from a right whale.
- Photo by Tom Kleindinst, WHOI

Ethical, legal, and logistical considerations make it impossible to experiment on living North Atlantic right whales in the wild. Instead, scientists have turned to the use of biopsies, or small tissue samples, and recent strandings to obtain experimental material. What can these opportunistic samples tell us about the fragile populations of the North Atlantic right whale?

That was the question that Joy Lapseritis set out to address in her doctoral dissertation as a graduate student in the MIT-WHOI Joint Program in Biological Oceanography. Marine mammals have always fascinated Lapseritis, and when she joined the research group led by Mark Hahn at WHOI, she knew she was going to find a way to study these gentle giants of the sea. With funding from Woods Hole Sea Grant and NOAA's North Atlantic Right Whale Grant Program, Lapseritis embarked on her studies in collaboration with other scientists studying the North Atlantic right whale. One aspect of her dissertation focused on the use of skin/blubber biopsies to obtain tissue samples for comparative biochemistry and molecular characterization of contaminant susceptibility genes and other biomarker genes related to contaminant effects and physiological condition.

Many scientists have used skin/blubber biopsies in their investigations of the North Atlantic right whale. The samples of skin and blubber are taken by a small dart shot from a crossbow. The procedure is minimally invasive. Biopsy samples are no larger than a couple of inches, yet they can yield valuable information on contaminant concentrations, genetic relationships among different animals, and quantitative information on blubber condition. In the past 15 years, researchers have sampled nearly two-thirds of the North Atlantic right whale population using the crossbow dart procedure. These small samples have allowed them to identify family trees, parental-offspring relationships, sex ratio of the sampled population, and the physiological and nutritional condition of the present population. Lapseritis' data sets add information on basic toxicology and susceptibility to chemical contaminants.

Lapseritis wanted to use the biopsy samples to isolate RNA and clone cDNA encoding the North Atlantic right whale aryl hydrocarbon receptor (AHR). AHR is an important gene in determining the susceptibility of an animal to persistent organic pollutants. Previous research in the Hahn lab has shown that AHR can be used as a sensitive biomarker of contaminant response in other marine mammals and birds. With this background information in hand, Lapseritis could compare the properties of the North Atlantic right whale AHR to those of AHRs from other species of marine mammals to try to ascertain whether or not contaminants were a contributing factor to the fragility of North Atlantic right whale populations. Using biomarkers of contaminant exposure and toxicity could lead to new insights of potential toxic effects in the North Atlantic right whale.

To characterize the biochemical properties of AHR from the North Atlantic right whale, Lapseritis compared the binding affinity for dioxin with that of AHRs isolated from beluga whales, humpback whales, humans and mice. AHRs from the three species of whale share a high degree of similarity in amino acid sequences and binding affinity. The whale AHRs are distinctly different from mouse and human AHRs and intermediate in binding affinity between the high-affinity mouse AHR and the low-affinity human AHR. To approximate real-world conditions relevant to toxicological effects, Lapseritis used cell culture techniques to examine the transcriptional properties of the various AHRs. The results provide some interesting insights into how different chemical contaminants may activate toxic responses in different ways. These findings, although preliminary, could be important for understanding the relative contributions of PCBs versus PAHs to effects on North Atlantic right whale health. Further research is needed to understand how the AHRs are involved in endocrine function and reproductive biology in the North Atlantic right whale and other cetacean species.

Lapseritis will continue her research with marine mammals and the AHR receptor during summers in Woods Hole. But now her interests in toxicology and marine mammals have brought her to the classroom at Simon's Rock College of Bard in Great Barrington, Mass., where she just joined the faculty as an assistant professor. It's a bit like going home again for Lapseritis, as she graduated from Simon's Rock College in 1990 with an Associate of Arts degree before completing her Bachelor's degree in biology and marine science at Smith College. Among the various courses she will be teaching at Simon's Rock College are the biology of marine mammals and cell biology. She hopes to inspire some of her undergraduate students in continuing the work on the North Atlantic right whale by introducing them to these magnificent gentle giants.