The work of the late chemical ecologist/UC Davis professor Sean Duffey (1943-1997) lives on.

Chemical ecologist Yuko Ishida of Toyama, Japan, a former UC Davis post-doctoral researcher who shared the same lab--and the same bench--in Briggs Hall that Duffey did, is the lead co-author of a cover story recently published in the Proceedings of the National Academy of Sciences (PNAS) about an invasive species of millipede that secrets hydrogen cyanide as a defensive mechanism. (See research paper)

 Ishida and Duffey never met but they shared a love of science and chemical ecology, in addition to the same lab.

At the time of his death, Duffey was a professor and vice chair of the UC Davis Department of Entomology. When chemical ecologist/professor Walter Leal joined the UC Davis Department of Entomology faculty in 2000, he occupied the former labs of professors Duffey and Susumu Maeda (1950-1998) and memoralized their lives and work by naming his lab the “Honorary Maeda-Duffey lab.” 

Ishida worked in the Honorary Maeda-Duffey lab from May 2001 to November 2007 at UC Davis. 

“Yuko loves to tackle challenging problems and he is well prepared to solve them,” said Leal, former chair of the UC Davis Department of Entomology and now with the UC Davis Department of Molecular and Cellular Biology.

In their research, Ishida and co-lead author Mohammad Dadashipour and colleagues, Kazunori Yamamoto and Yasuhisa Asano, studied the millipede, Chamberlinius hualienensis. They  isolated a hydroxynitrile lyase (HNL) enzyme, which catalyzes the synthesis of various building blocks of fine chemicals and pharmaceuticals. Their findings suggest that “millipedes and other arthropods might be a valuable source of industrial biocatalysts.”

Ishida also photographed the millipede, found in southern Japan, for the PNAS cover.

The four scientists all work at the Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, and are affiliated with the Asano Active Enzyme Molecule Project, Exploratory Research for Advanced Technology, Japan Science and Technology Agency, Toyama.

“To discover more efficient and stable HNLs, we focused on the invasive cyanogenic millipede as a bioresource,” the scientists wrote. “The HNL identified from the millipede showed not only the highest specific activity toward benzaldehyde among known HNLs, including the almond HNL in industrial use, along with wide temperature and pH stabilities, but also high enantioselectivity in the synthesis of various cyanohydrins. These properties make it suitable as an industrial biocatalyst. Arthropods are likely to be valuable sources of potential biocatalysts for the next generation of industrial biotechnology.”

Duffey, who died unexpectedly at age 54 on May 21, 1997 of an embolism precipitated by a difficult-to-diagnose lung cancer, was a well-known chemical ecologist. He researched interactions involving chemicals, plants, and insects. His first studies were of the cardiac glycosides produced by milkweeds (Asclepiadaceae) and their sequestration by the insects that fed on them. His primary efforts concentrated on the milkweed bugs, Oncopeltus fasciatus and Lygaeus kalmii, but he also worked with monarch butterflies and milkweed beetles. “Among his important discoveries was the fact that a biophysical system was operating in the sequestering of cardiac glycosides,” wrote UC Davis entomologists/professors James R. Carey, Hugh Dingle and Diane Ullman in their tribute to him. “While continuing his research on cardiac glycosides, Duffey began an analysis of the remarkable cyanogenic defensive secretions of Polydesmid millipedes.”

 “There followed several papers on the biochemistry of HCN production and the production of other defensive compounds in these interesting animals,” they wrote. “After arriving at UC Davis, Sean began a long series of brilliant studies on the chemical mechanisms used by plants to fend off attack by insects and various pathogens. This work centered on resistance in tomatoes, and over the years he collaborated with numerous students and colleagues. Studies analyzed the role of numerous chemicals produced by plants including tomatine, proteinase inhibitors, and various plant oxidative enzymes. Recent studies had included analyses of induced defenses and the interactions of chemicals with the biological agents such as parasitoids and baculoviruses used in various IPM and biological control programs.”

“A constant theme and frequently emphasized message in Sean's work was the fact that chemical-biological interactions were rarely simple and straightforward,” they wrote. “He stressed that in order to understand plant-insect interactions, for example, it was necessary to understand the interactions among plant chemicals, the overall characteristics of the insect's diet, the physiological state of the insect, and the modifiable characteristics of plant and insect. Chemical and biological context and chemical mixture were seen as critical determinants of biological activity; a simple view that natural products functioned merely as "toxins" or isolated defensive factors was often misleading.”

Carey, Dingle and Ullman praised  Duffey's "truly interdisciplinary research that included several joint projects with members of the Entomology Department and also with colleagues in the departments of Nematology Ecology and Plant Pathology. We all experienced Sean insisting over and over that interactions are not simple and that one must understand the chemistry, the physiology, and the ecology to really understand interactions between plants, insects, and their pathogens. Sean's legacy is an outstanding record of how to go about studying plant-insect interactions, not just the gathering of data on interactions that occur.”

The legacy continues...

They are two who make a difference.

Native pollinator specialist Robbin Thorp, emeritus professor of entomology, received the 2015 Distinguished Emeritus Award and Hugh Dingle, emeritus professor of entomology, received an Edward A. Dickson Emeritus Professor Award at the chancellor's luncheon on Monday, Feb. 23 in the UC Davis Pavilion.

The two emeriti professors from the UC Davis Department of Entomology and Nematology were among those honored at the event.  UC Davis Chancellor Linda P. B. Katehi, Provost Executive Vice Chancellor Ralph Hexter, and  emcee Bill Rains, past president of the UC Davis Emeriti Association, praised them for their work.


Robbin Thorp
Thorp was singled out for the distinguished emeritus award for his outstanding scholarly work and service accomplished since his retirement in 1994. "Dr. Robbin Thorp should be the first scientist to be cloned," said emcee Rains, quoting James Cane of the USDA-ARS Pollinating Insect Research Unit, Utah State University, Logan 

Thorp, who joined the UC Davis entomology faculty in 1964 and achieved emeritus status in 1994, is a state, national and global authority on pollination ecology, ecology and systematics of honey bees, bumble bees, vernal pool bees, conservation of bees, contribution of native bees to crop pollination, and bees of urban gardens and agricultural landscapes.

Since his retirement, he has compiled an exemplary record for his research, teaching, publications, presentations, and advisement services, sharing his expertise with local, statewide, national and international audiences. In his retirement, he has published 68 papers and is the first author on 15 publications. He received several prestigious awards: the 2013 outstanding team award, with several colleagues, from the Pacific Branch of the Entomological Society of America, and the 2010-2011 Edward A. Dickson Emeriti Professorship, UC Davis. Thorp is the North American regional co-chair for the International Union for Conservation of Nature (IUCN) Bumblebee Specialist group.   He is a member of 10 professional societies, including the International Society of Hymenopterists.

A fellow of the California Academy of Sciences since 1986 and a world authority on bumble bees and other native bees, Thorp keynoted the Smithsonian Institution's public symposium on “The Plight of the Bumble Bees” in June of 2009 in Washington D.C., delivering a presentation on “Western Bumble Bees in Peril.”  He continues to monitor bumble bee populations in California and Oregon, including Franklin bumble bee (Bombus franklini), which he fears may be extinct. He has sounded the alarm on protecting bumble bees.

Thorp maintains his office and research headquarters in the Harry H. Laidlaw Jr. Honey Bee Research Facility on the UC Davis campus. Among his latest publications: he co-authored two books published in 2014:  Bumble Bees of North America: An Identification Guide (Princeton University Press) and California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday). Of the 20,000 bee species identified worldwide, some 4000 are found in the United States, and 1600 in California.

Thorp spends much of his time in the Bohart Museum of Entomology, which houses collections critical to his bee identification work. He identifies species and regularly volunteers at the open houses and other event.

Thorp is an integral part of The Bee Course, an annual 10-day workshop sponsored by the American Museum of Natural History and held at the Southwestern Field Station near Portal, Ariz. He has taught there since 2002 (the instructors are all volunteers), and even though he is 81 years young, he plans to continue teaching there.  (See more on the departmental web page.)

Hugh Dingle

Hugh Dingle. an international authority on animal migration, received a Dickson award to help fund his research on monarch butterflies, “Monarchs in the Pacific: Is Contemporary Evolution Occurring on Isolated Islands?” Monarch butterflies established just 200 years ago in remote Pacific islands are undergoing contemporary evolution through differences in their wing span and other changes, he believes.

Dingle, author of two editions of Migration: The Biology of Life on the Move, said his previous studies reveal that migrant and resident monarchs exhibit different wing shapes. He will be working with community ecologist/associate professor Louie Yang and molecular geneticist/assistant professor Joanna Chiu of the UC Davis Department of Entomology and Nematology to examine the ecology and physiology of monarch butterflies (Danaus plexippus) in three islands where contemporary evolution might be expected. The islands are Oahu (Hawaii), Guam (Marianas) and Weno (Chuuk or Truk).

“This is the necessary first step in a long-term analysis of the evolutionary ecology and physiology of monarch butterflies on remote Pacific islands,” said Dingle, a fellow of the American Association for the Advancement of Science and the Animal Behavior Society.

Dingle said the monarch, widely distributed “for eons” in the New World, is fairly new to the Pacific islands and to Australia. “In addition to North America, the monarch occurs as a resident throughout the Caribbean and Central and northern South America—and probably as a migrant farther south. One of the more intriguing aspects of its distribution is that beginning in the early part of the 19th century, it spread throughout the Pacific all the way to Australia, where there are now well-established."

An analysis of a monarch population in Hawaii shows that resident monarchs have shorter, broader wings than the long-distance migrants. The Hawaii butterfly wings were shorter than the eastern U.S. long-distance migrants, but “not so short-winged as the residents in the Caribbean or Costa Rica, which have been present in those locations for eons, rather than the 200 years for Hawaii.”

“If there are indeed wing shape changes associated with evolution in isolation, are there other changes that may have occurred under selection and local adaptation for residency?” Dingle wonders. “Are there other changes that may have occurred under selection and local adaptation for residency? Examples of such traits might be changes in flight muscle physiology, changes in photoperiodic diapause response, changes in the characteristics of orientation ability and its relation to antennal circadian rhythms, or changes in the reproductive capacity or tactics (re-colonization of ‘empty' habitats is no longer part of the life cycle).

Dingle published the second edition of Migration: The Biology of Life on the Move (Oxford University Press) in November 2014. It is the sequel to the widely acclaimed first edition, published in 1996. National Geographic featured Dingle in its cover story on “Great Migrations”  in November 2010.  LiveScience interviewed him for its November 2010 piece on “Why Do Animals Migrate?” (See more on the departmental web page.)

Congratulations, Distinguished Professor Emeritus Robbin Thorp, and Dickson Professorship Awardee Hugh Dingle!

(Note: This blog, Bug Squad, focuses on entomology. Other recipients of the Dickson award were Daniel Anderson of the Department of Land, Air and Water Resources; Martha Macri of the Department of Linguistics; and Peter Schiffman, Department of Geology. (See web page.)

Like the migratory animals that he studies, Hugh Dingle, emeritus professor of entomology at the University of California, Davis, is on the move.

Dingle, who served as a professor in the UC Davis Department of Entomology from 1982 to 2002, achieving emeritus status in 2003, recently published the second edition of Migration: The Biology of Life on the Move (Oxford University Press), a sequel to the first edition published in 1996.

A worldwide authority on animal migration, Dingle says the full understanding of migration, or “life on the move,” involves genetics, physiology, and morphology, as well as behavior and ecology. Among the animals that migrate: whales, monarch butterflies, armyworm moths, pelicans, locusts, winged aphids and ballooning spiders.

Dingle has researched in seven countries: UK, Kenya, Thailand, Panama, Germany and  Australia, as well as the United States. National Geographic featured him in its cover story on “Great Migrations”  in November 2010.  LiveScience interviewed him for its November 2010 piece on“Why Do Animals Migrate."

Now Dingle will be heading to the Pacific islands to study monarchs. He just received the UC Davis Edward A. Dickson Professorship Award to research “Monarchs in the Pacific: Is Contemporary Evolution Occurring on Isolated Islands?”

Monarch butterflies established just 200 years ago in remote Pacific islands are undergoing contemporary evolution through differences in their wing span and other changes, Dingle believes. He will be working with community ecologist Louie Yang and molecular geneticist Joanna Chiu, assistant professors in the UC Davis Department of Entomology and Nematology, to examine the ecology and physiology of monarch butterflies (Danaus plexippus) in three islands where contemporary evolution might be expected. The islands are Oahu (Hawaii), Guam (Marianas) and Weno (Chuuk or Truk).

“This is the necessary first step in a long-term analysis of the evolutionary ecology and physiology of monarch butterflies on remote Pacific islands,” said Dingle, a fellow of the American Association for the Advancement of Science and the Animal Behavior Society.

The monarch, widely distributed “for eons” in the New World, is fairly new to the Pacific islands and to Australia. He speculates that the monarchs arrived in the Pacific islands with their host plant, milkweed, which was valued at the time for its medicinal properties.

An analysis of a monarch population in Hawaii shows that resident monarchs have shorter, broader wings than the long-distance migrants. The Hawaii butterfly wings were shorter than the eastern U.S. long-distance migrants, but “not so short-winged as the residents in the Caribbean or Costa Rica, which have been present in those locations for eons, rather than the 200 years for Hawaii.”

“If there are indeed wing shape changes associated with evolution in isolation, are there other changes that may have occurred under selection and local adaptation for residency?” Dingle wonders. “Are there other changes that may have occurred under selection and local adaptation for residency? Examples of such traits might be changes in flight muscle physiology, changes in photoperiodic diapause response, changes in the characteristics of orientation ability and its relation to antennal circadian rhythms, or changes in the reproductive capacity or tactics (re-colonization of ‘empty' habitats is no longer part of the life cycle)."

“Diapause and fat storage, necessary to support migration, are triggered by short photoperiods,” Dingle said, “and the butterflies orient using a sun compass synchronized to a circadian rhythm in the antennae." Overwintering sites in North America include the Transvolcanics Mountains of central Mexico, and the California Coast, particularly Santa Cruz, Pismo Beach, and Pacific Grove.

The UC Davis team will study the monarchs on the three islands and compare them with California mainland monarchs. Using an image analyzer and camera equipment available in Yang lab, the team will photograph “chilled” butterflies in a fixed position with wings spread and then release them back into the wild. The image analyzer will measure different variables, including length, width and angles from the photographs and compute multivariate-shape parameters.

The Chiu lab will assess genetic differences using a transcriptomic approach with monarch caterpillars. “This assessment will be greatly facilitated by the fact that the monarch genome has now been sequenced,” Dingle noted. “A major focus of Dr. Chiu's research is circadian rhythm genes, and these will be especially relevant here because of the association of these genes with monarch capabilities. Because the monarch cell line is cycling and has a functional circadian clock, effects of mutations in specific clock genes can be examined with regard to clock function.”

Dingle expects the one-year research program not only to form the basis for “long-term research on the evolutionary genetics of behavior, ecology and physiology on Pacific island monarch butterflies” but on “the general aspects of island biogeography, a subject of great practical theoretical interest in evolutionary biology.”

That's exciting research. We look forward to the results!

Lately we've been fascinated by the migrating Monarch butterflies (Danaus plexippus) heading to coastal California and central Mexico for their overwintering sites.

For years we've marveled at the migrating whales passing Point Reyes as we stood glued to our binoculars.

And we've expressed awe that a bird--a plover--makes nonstop flights over the central Pacific Ocean from Alaska to Australia and New Zealand.

Amazing. Nothing short of incredible, especially when you consider that many homo sapiens can't find their way out of a parking lot.

They're all on the move. But how many of us have seen the lesser known migrants, such as winged aphids, ballooning spiders, mites, locusts, pelicans, grasshoppers, and armyworm moths, on the move?

Enter Hugh Dingle, an emeritus professor of entomology at the University of California, Davis, and a worldwide authority on animal migration.

Dingle, who was featured in National Geographic's cover story on "Great Migrations in November 2010 and interviewed by LiveScience for its November 2010 piece on “Why Do Animals Migrate?", has just published the second edition of his book, Migration: The Biology of Life on the Move (Oxford University Press), a sequel to the first edition published in 1996.

The full understanding of migration, or “life on the move,” involves genetics, physiology, and morphology, as well as behavior and ecology, Dingle says.

"The program or syndrome includes specific modifications of metabolic physiology like enhanced fat storage to fuel migration and of sensory systems to detect inputs from the sun, stars, and magnetic field lines to determine compass direction. Intimately involved in the latter are daily and yearly biological clocks. The pathway followed is an outcome of the syndrome of migratory behavior and is part of the ecology that provides the natural selection acting to determine the evolution of migration.”

Not all migration is a round trip; sometimes it's one-way, Dingle says.  “Important defining behavioral characteristics are specific departure and arrival tactics and the refusal to stop even in favorable habitats until the migration program is complete,” Dingle says. “In the words of National Geographic reporter David Quammen migrants ‘are flat-out just gonna get there.'"

Why is it important to understand the biological basis of migration and its evolution? “Because migration is so widespread and because migrants have such impact on both natural and man-altered ecosystems,” says Dingle, who achieved emeritus status in 2003 after serving on the faculty of the UC Davis Department of Entomology (now the UC Davis Department of Entomology and Nematology) from 1982 to 2002.

In his book, Dingle covers the interaction between behavior and outcome. Another important focus: he covers the relation between migration and life histories, including the evolutionary genetics of the relationship. Long-distance round-trips, for example, require long lifespans, hence most insects, although not all, migrate only one-way.  

“Natural selection acts differently on long versus short lives," Dingle says. "With long lives there are usually many opportunities to produce offspring; with short lives there may be only one. Thus reproductive opportunities may determine when and where to migrate. Migrating aphids postpone reproduction until they colonize new host plants; birds reproduce following migration in the spring, but not in the fall. Some birds and insects use migration to exploit ‘rich patches' and breed in different places in different years or even in the same year."

Dingle, former secretary of the International Society for Behavioral Ecology and past president of the Animal Behavior Society, says he wrote the book for "students of migration and for those biologists who are generally interested in the functioning and adaptations of whole organisms."

Dingle is a fellow of the American Association for the Advancement of Science and the Animal Behavior Society. His research has taken him throughout the world, including the UK, Kenya, Thailand, Panama, Germany and  Australia.

In some respects, he, too, migrated.