Encyclopedia of Living Things and Scents/PheromonesBook Review

Edited by Kazushige Touhara, Yoshito Niimura, Yoshihiro Yoshihara, Makoto Yokosuka, Kenshi Kikusui, and Masako Okamoto
Asakura Publishing, published June 1, 2025, 15,000 yen (+ tax)

This book is a textbook on odors and pheromones compiled by happy scientists who became world-class researchers while holding onto the simple question, "What is an animal?" Not only is it an essential addition to any zoology laboratory's library, but it also serves as a guiding light for students aspiring to become researchers, as well as graduate students and young researchers unsure of their career paths, prompting them to ponder what scholarship truly is.

Smells and pheromones, namely the olfactory and vomeronasal systems, are not shared primitive traits among animals. However, they are among the most primitive sensory systems that animals have evolved to perceive the external world, and they constitute a biological system that plays an essential role in how animals interact with their environment as living beings. "Where do odorants come from? Most of them are compounds produced within the bodies of living organisms such as plants, insects, animals, and microorganisms, and emitted outside the body" (p. 3, Tohara). Are the fragrances of flowers and fruits emitted by plants to attract animals, or are they merely perceived that way by animals? On the night of a gathering in Aburatsubo hosted by Professor Yoshitaka Oka, I discussed this question with the editor, Professor Makoto Yokosuka, and I still fondly remember it, along with the starry sky we looked up at on that occasion.

The concept of pheromones can trace its origins back to Fabre's Book of Insects. Previously, the vomeronasal system, which is the pheromone sensory system, was viewed as an accessory olfactory system subordinate to the (main) olfactory system. However, as research has progressed, it has become clear that the vomeronasal organ is not merely an auxiliary organ, but a highly independent sensory system specialized in reproduction, social behavior, aggressive behavior, mother-infant recognition, and more. Numerous compounds have been identified, ranging not only from sex pheromones to those involved in reproduction, such as the suppression of ovulation and ovarian development, but also those involved in social behaviors such as aggression, aggregation, trail-following, alarm, and caste differentiation. Discussions have also begun regarding phylogenetic changes and evolutionary commonalities in their reception mechanisms, and research into how odors and pheromones trigger animal behaviors and physiological changes—approaching the very essence of animals—has advanced significantly. On the other hand, in many vertebrates such as fish and birds, the vomeronasal organ itself does not exist, or the main olfactory system also receives pheromones. Numerous examples have been found that cannot be explained by the dichotomy of "main" and "accessory."

This book is a comprehensive encyclopedia that systematically organizes knowledge regarding the olfactory and vomeronasal systems, ranging from invertebrates such as bacteria, yeast, nematodes, and insects, to fish, amphibians, reptiles, birds, mammals such as rodents and non-human primates, and ultimately humans. Furthermore, it pays attention to applied fields such as plant odor sensing, odor countermeasures, and the repelling of harmful animals and pests, possessing a scope befitting its title, "Living Organisms and Odors."

However, there seems to be another meaning imbued in the title "encyclopedia" of this book. Research is also an endeavor that generates new concepts to define terms, or redefines existing terminology. Particularly in zoology, which deals with ambiguous endpoints such as behavior and physiological changes, the research field of "odors and pheromones" has dramatically advanced its conceptual organization in recent years. In this book, the editors and authors, acting as scientists, have chosen their terminology with extreme care, organized the entries, and paid meticulous attention to the original source literature. That attitude itself embodies an academic stance worthy of an "encyclopedia." At the same time, I felt that the book also sends a quiet message to graduate students and young researchers: "This is how science ought to be."

In Japan, zoology has traditionally been the study of exploring the principles of animals themselves, with its applications handled by adjacent fields such as veterinary science, fisheries science, medical science, and neuroscience. Research on the olfactory and vomeronasal systems is also a field where Japanese researchers have led the world. Professors Hideto Kaba and Yuji Mori, who supported its dawn, were researchers in veterinary science, while Professor Kensaku Mori was a researcher in medical science. On the other hand, there are not a few researchers like Professors Masumi Ichikawa and Hiroshi Ueda, who grew up within the Zoological Society, built the foundations of this field, and continue to stay close to the society. Furthermore, Honorary Members Susumu Ishii and Yoshitaka Oka fostered interdisciplinary collaboration centered around the Zoological Society and nurtured many researchers, including Kubokawa, who is also a contributor to this book. Moriya, Yokosuka, and others can also be said to be the children and grandchildren of the Zoological Society within this lineage. This book clearly etches the history of the Zoological Society of Japan nurturing young researchers over many years and its academic lineage.

The representative editor, Tohara, is a leading agricultural chemistry researcher who has pioneered a new horizon in "odor and pheromone" research by fusing authentic chemical foundations with cutting-edge analytical technology. Without going into detail, he has always maintained a deep respect for the pioneers who supported the dawn of the field and has cherished his interactions with them. I would also like to add that these pioneers have spoken of Tohara's success as if they were rejoicing in the growth of their own child. In this way, this book is undoubtedly a masterpiece tied to the lineage of the Zoological Society. It is a collaborative work between the Japanese researchers who supported the dawn era and those who opened the next door, and is nothing less to a "encyclopedia" that fuses authentic scientific methodology with cutting-edge technological innovation and discovery. It is a volume of exceptionally high value, both as a collection for libraries and laboratories, and as a guiding light for young researchers in science.

Seishin Kakeyama (Faculty of Human Sciences, Waseda University)

Encyclopedia of Organisms, Scents, and Pheromones (PDF file)