School of Aquatic and Fishery Sciences

By Michelle Ma
This article originally appeared in UW News

Parasites have a public relations problem.

Unlike the many charismatic mammals, fishes and birds that receive our attention (and our conservation dollars), parasites are thought of as something to eradicate — and certainly not something to protect.

But only 4% of known parasites can infect humans, and the majority actually serve critical ecological roles, like regulating wildlife that might otherwise balloon in population size and become pests. Still, only about 10% of parasites have been identified and, as a result, they are mostly left out of conservation activities and research.

An international group of scientists wants to change that. About a dozen leading parasite ecologists, including University of Washington’s Chelsea Wood, published a paper Aug. 1 in the journal Biological Conservation, which lays out an ambitious global conservation plan for parasites. Wood teaches FISH 406: Parasite Ecology annually in the autumn quarter.

“Parasites are an incredibly diverse group of species, but as a society, we do not recognize this biological diversity as valuable,” said Wood, an assistant professor in the UW School of Aquatic and Fishery Sciences. “The point of this paper is to emphasize that we are losing parasites and the functions they serve without even recognizing it.”

The authors propose 12 goals for the next decade that could advance parasite biodiversity conservation through a mix of research, advocacy and management.

“Even though we know little to nothing about most parasite species, we can still take action now to conserve parasite biodiversity,” said Skylar Hopkins, paper and project co-lead and an assistant professor at North Carolina State University.

Perhaps the most ambitious goal is to describe half of the world’s parasites within the next 10 years. Providing taxonomic descriptions allow species to be named, which is an important part of the conservation process, the researchers said.

“If species don’t have a name, we can’t save them,” said Colin Carlson, the other project co-lead and an assistant professor at Georgetown University. “We’ve accepted that for decades about most animals and plants, but scientists have only discovered a fraction of a percentage of all the parasites on the planet. Those are the last frontiers: the deep sea, deep space, and the world that’s living inside every species on Earth.”

Importantly, the researchers stress that none of the parasites that infect humans or domesticated animals are included in their conservation plan. They say these parasites should be controlled to safeguard human and animal health.

The paper is part of an entire special edition devoted to parasite conservation. Wood is the lead author on one study in the collection that finds the responses of parasites to environmental change are likely to be complex, and that a changing world probably will see both outbreaks of some parasites and a total loss of other parasite species.

Parasites often need two or more host species to complete their lifecycle. For example, some parasites first infect fish or amphibians, but ultimately must get transmitted to birds to reproduce and multiply. They ensure that this happens through ingenious ways, Wood explained, often by manipulating the behavior or even the anatomy of their first host to make these fish or amphibians more susceptible to being eaten by birds. In this way, the parasite then gets transmitted to a bird — its ultimate destination.

“We need to recognize that there will be a diversity of responses among parasite taxa and not take for granted that every parasite is dwindling toward extinction or about to cause a major outbreak,” Wood said.

Given this dynamic, Wood and colleagues wanted to see what would happen to the abundance of parasites if the ecosystems in which they live changed. They designed an experiment across 16 ponds in central California’s East Bay region. In half of the ponds, they installed structures such as bird houses, floating perches and mallard decoys intended to attract more birds, thus temporarily altering the natural ecosystem and boosting biodiversity in these ponds.

After a couple of years, the researchers analyzed parasite biodiversity in each of the 16 ponds. What they found was a mixed bag: Some parasite species responded to elevated bird biodiversity by declining in abundance. But other parasites actually increased in number when bird biodiversity increased. The authors concluded that as biodiversity changes — due to climate change, development pressure or other reasons — we can expect to see divergent responses by parasites, even those living within the same ecosystem.

Traditionally, the field of disease ecology assumes one of two paths: That we are either heading toward a future of more disease and massive outbreaks or toward a future of parasite extinction. This paper shows that both trajectories are happening simultaneously, Wood explained.

“This particular experiment suggests that we need to anticipate both trajectories going forward. It starts to resolve the conflict in the literature by showing that everyone is right — it’s all happening,” Wood said. “The trick now is to figure out what traits will predict which parasites will decline and which will increase in response to biodiversity loss.”

Wood’s lab is working on that question now by reconstructing the history of parasites over time, documenting which parasites increased in abundance and which declined. However, there’s almost no historical record of parasites and without this information, it’s difficult to know how to conserve them. By dissecting museum specimens of fish, the researchers are identifying and counting various parasites found in the specimens at different places and times.

“These pickled animals are like parasite time capsules,” Wood explained. “We can open them up and identify the parasites that infected a fish at its death. In this way, we can reconstruct and resurrect information that previously we didn’t think was possible to get.”

Co-authors on this paper are Pieter Johnson and Margaret Summerside of the University of Colorado Boulder. This research was funded by the Michigan Society of Fellows, National Science Foundation, Alfred P. Sloan Foundation, the University of Washington, the University of Colorado, the National Institutes of Health and the David and Lucile Packard Foundation.

See the journal for the full list of authors and funders for the special edition.

For more information, contact Wood at chelwood@uw.edu and Hopkins at hopkins@nceas.ucsb.edu.

By UW News staff
This article originally appeared in UW News

Deep-sea anglerfishes employ an incredible reproductive strategy. Tiny dwarfed males become permanently attached to relatively gigantic females, fuse their tissues and then establish a common blood circulation. In this way, the male becomes entirely dependent on the female for nutrient supply, like a developing fetus in the womb of a mother or a donated organ in a transplant patient. In anglerfishes, this unusual phenomenon is called “sexual parasitism” and contributes to the reproductive success of these animals living in the vast space of the deep sea, where females and males otherwise rarely meet.

Now scientists from the Max Planck Institute of Immunobiology and Epigenetics in Germany and the University of Washington have figured out why female anglerfishes so readily accept their male mates. Their findings are published July 30 in Science.

The extraordinary reproductive strategy employed by deep-sea anglerfishes has posed an enigma that has persisted for a century, ever since the first attached fishes were discovered by an Icelandic fisheries biologist in 1920.

“How is it possible that genetically similar organisms — in this case, members of the same species — accept each other so readily when tissue rejection is the usual and expected result of any such union?” said co-author Ted Pietsch, professor emeritus at the UW School of Aquatic and Fishery Sciences. “Just witness the difficulties surrounding organ transplantation in humans. We now see great potential down the road for a better understanding of the problem.”

Deep-sea anglerfishes are found in all oceans around the world, yet the roughly 160 known species are extremely rare. They lure their prey in the inky-black ocean darkness at depths between 300 and 5,000 meters (980 and 16,400 feet) using a bioluminescent fishing apparatus placed on the tip of the snout — hence the “angler” in their common name. Their enormous, toothy mouth and expandable stomach enable them to capture and devour prey larger than themselves in a single instantaneous gulp.

Deep-sea anglerfish males are a fraction of the size of the females — in the most extreme cases, females may be more than 60 times the length and about a half-a-million times as heavy as the males. The males don’t have a luring apparatus; instead, most have large, well-developed eyes and huge nostrils, which help them home in on a species-specific chemical attractant emitted by the females.

For decades, researchers have wondered how this rare phenomenon happens in anglerfish. Several years ago, Dr. Thomas Boehm, a medical doctor and immunologist at the Max Planck Institute of Immunobiology and Epigenetics in Germany, and the UW’s Pietsch, an ichthyologist and the world’s expert on anglerfishes, set out to study the genomes of different anglerfish species.

They began by looking at the structure of major histocompatibility (MHC) antigens. These molecules are found at the surface of the body’s cells and signal alarm to the immune system, when the cells are infected by a virus or a bacterium.

To make sure that all pathogens are efficiently recognized, the MHC molecules are extremely variable, so much so that it is hard to find identical or near-identical forms in any two individuals of a species. This feature is at the root of the tissue-matching problem that plagues human organ and bone marrow transplantation. To their great surprise, the researchers found that anglerfishes that utilize permanent attachment largely lack the genes that encode these MHC molecules, as if they had done away with immune recognition in favor of tissue fusion.

Additionally, they found that the function of killer T cells, which normally eliminate infected cells or attack foreign tissues during the organ rejection process, was also severely blunted, if not lost entirely, in anglerfishes. Further analysis also indicated that antibodies, another powerful weapon in the arsenal of immune defense, are missing in some anglerfish species.

“For humans, the combined loss of important immune facilities observed in anglerfishes would result in fatal immunodeficiency,” Boehm said.

The researchers found that anglerfishes lack the genes responsible for tissue rejection and instead use much improved innate facilities to defend themselves against infections, a most unexpected solution to a problem that is faced by all living things. In other words, their new type of immune system is very unusual among the tens of thousands of vertebrate species.

The study thus shows that despite several hundred million years of co-evolutionary partnership of innate and adaptive functions, vertebrates can survive without the adaptive immune response previously considered to be irreplaceable.

“We find it remarkable that the unusual mode of reproduction was invented several times independently in this group of fishes,” Pietsch said.

Although the details of the improved innate immune response in anglerfishes remain to be discovered, the results of this study point to potential strategies that enhance innate immune facilities in human patients who suffer the consequences of inborn or acquired impairment of immune facilities.

Other co-authors are Jeremy Swann, Stephen Holland and Malte Petersen of the Max Planck Institute of Immunobiology and Epigenetics.

This work was supported by the Max Planck Society, the Ernst Jung Foundation for Science and Medicine, the European Research Council and the National Science Foundation.

For more information, contact Pietsch at twp@uw.edu and Boehm at boehm@ie-freiburg.mpg.de.

This post was adapted from a Max Planck Institute of Immunobiology and Epigenetics release.

Suppose there is an endangered species of frog that is declining in abundance. A group of natural resource managers come together and ask, “what can we do?”

The answer? It depends.

While not the most uplifting of truths, it illustrates the challenges and complexity of these types of issues and the many factors that must be considered.

In their most recent book, Sarah Converse (unit leader, USGS Washington Cooperative Fish and Wildlife Research Unit, and UW associate professor in Aquatic and Fishery Sciences and Environmental and Forest Sciences) and her co-editors (Michael Runge, James Lyons, and David Smith, all of whom are scientists with USGS) explore how managers can learn to navigate such situations. They describe how a structured decision-making approach uses careful and organized analysis to aid in solving natural resource problems. Their book, Structured Decision Making: Case Studies in Natural Resource Management, was published in May by Johns Hopkins University Press.

The book contains various case studies from the United States, Canada, Australia, and Mauritius. These case studies examine a rich variety of topics, including keeping forest birds free from disease, conserving imperiled freshwater mussels, dealing with coastal wetlands in the face of sea-level rise, and combating invasive alpine shrubs.

Using the above hypothetical of the endangered frog, Converse explains the different approaches managers would use by identifying the possible desired outcomes:

Is the goal to determine whether this species of frog should be given federal protection? If yes, that is a particular type of decision that the U.S. Fish and Wildlife Service (USFWS) must make in the United States, subject to their own laws and practices.

Is the decision about what a state wildlife agency can do to conserve this frog species? If yes, then the decision is about how to use state resources in the most effective way possible to manage the species on the ground.

Or, is the question about how to conserve this species on private land? If yes, the decision is about how natural resource managers and their respective agencies and organizations could build effective partnerships with private landowners.

In each instance, Converse points out that the who, what, where, and when are different, and it is often unclear which decision is the right one to focus on at the outset. By examining the desired outcomes and issues carefully and independently within a comprehensive framework, it is possible to improve the quality of decision making.

It is definitely one of those concepts that is much more “show” than “tell.” You really have to see the principles and tools in action to develop an understanding of the power of structured decision making.

SAFS caught up with Converse for a conversation about this recently published book and how it may be used by decision-makers to tackle challenging issues.

How did you and the other editors identify the need for this book? Is it the first of its kind?

Sarah Converse: Yes, this is the first book of case studies in structured decision making for natural resource decision-making problems. We recognized the need for this book because we spend a lot of time teaching people what structured decision making is and how they can dig in and use it for their issues and problems. But, it is definitely one of those concepts that is much more “show” than “tell.” You really have to see the principles and tools in action to develop an understanding of the power of structured decision making.

Back in 2007, we started running workshops in structured decision making at the USFWS National Conservation Training Center in West Virginia. For these workshops, we invited groups to work through real decision problems with experienced decision analysts over the course of one week. The reports that these teams wrote were so obviously an important teaching resource—demonstrating how to apply structured decision making to natural resource problems—we knew we had to get them out in an accessible form. Each of the case studies in the book arose from a real problem to which a group of people applied the principles of structured decision making.

The groups who worked on the case studies presented in the book were each composed of a combination of decision analysts, scientists, and decision-makers from management agencies, such as the US Fish and Wildlife Service, state management agencies, and others. What is important about this is that the case studies in the book by and large resulted in real decisions made by these management agencies—they weren’t just academic exercises. This is an important aspect of the book: it describes how these tools can be used in real situations where the stakes are high.

What is something new in the book that you would like people to know?

S.C.: It isn’t new exactly, but it is something that we have learned over the years: when it comes to solving hard problems in natural resource management, sometimes the biggest challenge is identifying the key decision or decisions to be made. There is so much complexity in the environmental problems we face that we can get stymied by all that complexity and end up stuck. Structured decision making is about helping people create a map to find their way out of the place where they’re stuck. The first step in creating that map is simply asking “Who needs to make what decision, where, and when?” If we can develop a really clear answer to that question, we’ve made a lot of progress. It turns out that answering that question is much more complicated than people realize.

Does this book work as a “template” to help decision-makers make unbiased decisions?

S.C.: Yes, the book is meant to provide a kind of template because all decisions are composed of a consistent set of components, and the trick is figuring out how to decompose the decision into those components. The idea of an “unbiased” decision is something I have to unpack. First, it is important to recognize that there is no such thing as an “objective” decision; all decisions are inherently subjective because we make them to achieve things we value, and values are inherently subjective. This is why science cannot tell us what to do (even though we hear this in common parlance all the time: When people say “X decision-maker is not doing what the science tells us to do,” that person is assuming a set of values that may or may not be held by that decision-maker. Science itself cannot tell us what to do because science doesn’t make statements about how the world “should be;” it makes statements about how the world is). The kind of “bias” that is counterproductive in decision making is when we let certain cognitive biases get in the way. For example, people tend to have a bias toward the status quo. They are familiar with it, so it feels safe, even when careful analysis would tell us that it is clearly suboptimal. Those are the kinds of biases we want to avoid, and structured decision making helps us do that.

Can you tell us some of the species and environments that have been impacted by this structured decision-making process?

S.C.: There are so many! Some of the case studies we cover in this book focus on whooping cranes, Mauritius olive white-eyes, fishes of the Great Barrier Reef, freshwater mussels, Indiana bats, and bighorn sheep. We also cover case studies that are focused on entire ecosystems, such as alpine peatlands, coastal wetlands, and large riverine systems. Something that we worked on close to home here in Washington is the South Sound Prairies ecosystem, where we considered how to build a network of reserves for several threatened species that inhabit that ecosystem, including the Mazama pocket gopher, the streaked horned lark, and the Taylor’s checkerspot butterfly.

What are some hurdles people will still encounter in natural resources decision making?

S.C.: So many things! Unfortunately, structured decision making doesn’t make hard problems easy, although it does give us a way through them. However, difficulties still remain: dealing with our natural cognitive biases, a perception that there isn’t enough time to spend thinking about a decision (the downside of this is that a lack of careful thought now can come back to haunt us later), real conflict, our natural tendency to be focused on solving the problem before we really know what the problem is…those are a few things that come to mind.

What was one case study that proved challenging, but was ultimately rewarding?

S.C.: All of them! Every problem I have ever worked on, at some point in the process, seemed really challenging. But similarly, I don’t think I’ve ever come out of a process and not felt like we had greater clarity about how to move forward.

Who is the target audience for this book?

S.C.: We wrote the book for students who are learning about natural resource science and management, scientists whose research informs natural resource management, and managers or decision-makers tasked with challenging natural resource management decisions.

To learn more about the book, read a recent JHU Press blog post by the editors.

For more information, contact Sarah Converse at sconver@uw.edu.