Thomas Eisner: Interpreter extraordinaire of nature's chemistry

On March 25, 2011, Thomas Eisner died after a long and courageous battle with Parkinson's disease. His tremendous legacy included founding and nurturing the scientific discipline of chemical ecology. Tom, though, might be the only person in the field to dispute his rights to the title, “Father of Chemical Ecology”—indeed, in one interview (1), he wryly opined that such claims cried out for DNA paternity tests.

Tom Eisner.

Born in Berlin, Germany, on June 25, 1929, Tom was the son of the gifted painter Margarete Eisner and the chemist Hans E. Eisner, a student of Nobel Laureate Fritz Haber. His parents’ accomplishments did little to protect the Jewish family from Nazi threats, and the Eisners left Germany in 1933, traveling to Barcelona, Spain, where Hans Eisner found work with a private chemical company. Soon thereafter the chaos of the Spanish Civil War led them to move again, first to France and then to Uruguay. Tom spent almost a decade in Uruguay, and during this relatively stable period of his life he developed his growing interest in natural history. After he graduated from high school, the family immigrated to the United States in the hope of finding greater educational opportunities for the children. Access proved difficult: Tom was rejected by Cornell University but was admitted to Champlain College in Plattsburg, NY. After two years he transferred to Harvard University, where he took his first course in entomology, sparking a lifelong fascination. After receiving a BA in 1951, he stayed four more years for a PhD, studying insects with Frank Carpenter and collaborating with fellow graduate student (and lifelong friend) Edward O. Wilson. After two years as a research associate at Harvard, Tom was hired as an assistant professor at Cornell. He remained there for his entire career, rising rapidly through the ranks and being named Jacob Gould Schurman Professor of Chemical Ecology in 1976. For 54 years, he kept on the wall of his office the framed original Cornell rejection letter he had received in 1947.

Tom's early work on morphology—among his first publications were analyses of the proventriculus of ants (2)—anticipated an important dimension of his entire career, notably, his uncanny ability to notice distinctive structural features and to see their significance in the life of the organism. Detecting invisible chemicals by their morphological signposts was Tom's forte; he determined functions for folds, wrinkles, and projections that systematists had meticulously described but never investigated. Elytral flanges of ground beetles defining membership in the subfamily Paussinae in the family Carabidae, for example, were shown to function as part of the equipment used as launching guides to direct and deflect toxic, boiling hot spray at predators, an application of technology familiar to aviation scientists as the Coandă effect (3). Feathery starbursts projecting from the abdomens of male bella moths and queen butterflies proved to be elaborate delivery devices for plant-derived aphrodisiacs (4). Color, too, was an important signpost for chemical communication—many chemically defended insects signal their toxicity with bright colors signifying distastefulness. Tom thus worked with some of the Class Insecta's most colorful members. Cochineal scale, for example, was known as a source of brilliant red pigment since Aztec times, but Tom was the first to document that the bitter-tasting pigment actually deters predators (5). With his refined aesthetic sense and amazing technical skills, he captured images of chemicals at work—sprays being discharged, beetles being spat out, spiders paralyzed by millipede alkaloids, fantastic fecal matter being brandished by tortoise beetles, and hundreds more, vividly rendering chemical communication visible to a broad audience, often developing novel photographic techniques to do so.

Cornell provided Tom with not only stellar students but also a superbly skilled and uniquely like-minded chemist with whom to collaborate. In a partnership that began in 1960, Tom published more than 130 of his 300+ refereed journal publications with Jerrold Meinwald. Together they determined the structure and function of defensive secretions, aphrodisiacs, glues, pigments, and pheromones, from chemical classes ranging from one-carbon hydrogen cyanide from oozing glands of millipedes to the 200-plus carbon macrocyclic polyamines in the trichomes of squash beetles, among the largest nonprotein natural products known. Beyond founding a new discipline linking the physical and biological sciences (long before such linkages became routine), Tom and Jerry demonstrated the utility of natural history studies to obtain scientific insights, the power of bioassays to ascertain ecological functions, and the value of embedding laboratory studies in ecological, behavioral, and environmental contexts. The two worked together to offer one of the nation's first courses in chemical ecology, and in 1990 to found the Cornell Institute for Research in Chemical Ecology, the first academic institute dedicated to the discipline. They also organized two collections of papers in chemical ecology and published them in PNAS as special features in 1995 and 2008 (http://www.nap.edu/openbook.php?isbn=0309052815; http://www.pnas.org/cgi/collection/chemical_ecology). Beyond academe, Tom coined the term and tirelessly promoted the concept of “chemical prospecting” as a tangible, economic justification for biodiversity conservation, a staple principle in chemical ecology (6). In addition to working together, Tom and Jerry played together: both accomplished musicians, they performed together on many occasions, with Jerry on flute and Tom at the piano.

From his peripatetic childhood, Tom gained fluency in French, German, Spanish, and English and an enduring interest in world affairs; visiting appointments were spent in The Netherlands, Panama, Germany, Australia, and Switzerland. He also traveled extensively around the United States, almost entirely by car. On one trip as a new assistant professor, he found the Archbold Biological Station in Lake Placid, FL; he became a regular visitor, and its dazzling biodiversity inspired many of his best-known studies. Tom's personal history also gave him a keen appreciation of how political policies can interfere with the conduct of science, and throughout his life he was an ardent defender of human rights and scientific freedom, serving on the National Academy of Sciences Committee on Human Rights and chairing the American Association for the Advancement of Science Subcommittee on Science and Human Rights for 8 years. He actively contributed to national debates on the biological effects of nuclear war, population control, and global climate change and appeared before Congress on multiple occasions, testifying on biodiversity conservation, endangered species legislation, and bioprospecting.

I was exceptionally fortunate to have met Tom early in my career, while I was a graduate student at Cornell. Tom was unfailingly an inexhaustible source of useful information on a staggering range of subjects and a relentless fount of encouragement and good cheer. For selfish reasons, my personal favorite among his 400+ papers involves a study of one of the most contemptible of insects, if familiarity breeds contempt. Pieris rapae, the imported European cabbageworm, is arguably America's most ubiquitous butterfly—occurring coast to coast and flying from early spring to late fall. As a caterpillar, it is a noxious pest of cabbage and other cole crops. In this thoroughly well-studied creature, Tom saw hairs with sticky globules, of unknown function. With Meinwald and others, Tom found that this Rodney Dangerfield of caterpillars produces a novel class of linolenic acid-derived natural products. To my unutterable delight, these generous scholars named these secretions mayolenes in my honor—and the image of the lowly cabbageworm that appeared in PNAS accompanying the article (7), with greatly magnified defensive hairs glistening like Christmas ornaments, is worthy of framing and hanging over a fireplace.

Finding beauty and chemistry in a cabbageworm, to me, epitomizes Tom's insatiable curiosity, remarkable intellect, and warm personality. He was a serious scientist who never lost perspective and never lost his sense of humor. As Parkinson's disease robbed him of the ability to hold and manipulate small objects (including his beloved insects), he remained philosophical; he once told me that he thought the disease might have been the consequence of a half-century of more or less constant exposure to oxidizing arthropod defensive secretions—condign retribution of a sort for poking, prodding, and often grinding up so many insects over the years.

Paternity or no, every chemical ecologist today in a sense owes his or her career to the vision and energy of Tom Eisner. Chemical ecologists are countable—a check of the membership list of the International Society for Chemical Ecology provides at least a rough approximation. What cannot be counted, however, are the thousands of individuals, in biology classes in school or at home watching the Public Broadcasting Service or reading For Love of Insects (8), who have been intrigued and inspired by Tom's work and who gained a greater appreciation of the scientific enterprise (and a greater admiration of the Class Insecta) as a result.

The bombardier beetle Stenaptinus insignis aims its hot quinonoid spray by precisely revolving the tip of its abdomen (reproduced from ref. 9).