Insect Symbiosis, vol. I

Kostas Bourtzis and Thomas A. Miller, Eds.
CRC Press
Boca Raton, FL
2003, 347 pp.
Price: $119.95
ISBN: 0-8493-1286-8

The field of microbe–insect mutualisms is a fascinating one, and it is rapidly changing as our understanding of the diversity and function of microbes inhabiting insects increases. In this book, Insect Symbiosis, the editors bring together some of the leading scientists in this diverse field to review specific questions confronting entomologists. But a book should be more than the sum of its parts, and this is where Insect Symbiosis could be improved. All in all, the book does some things well, but it lacks direction; and the reader is left without any sense of synthesis on the subject.

The book is separated into 18 chapters, 8 of which focus on sex-altering microbes, and the rest cover a range of other topics. This imbalance almost makes readers feel like they are reading two separate books! Chapters are about 10–15 pages long, and the quantity of illustrations vary considerably in quantity from chapter to chapter; some have no illustrations at all (e.g., Chapters 8 and 16). Some color plates are presented in the center of the book.

Although often used to refer to mutualistic associations, the term symbiosis can refer to a range of relationships between dissimilar organisms living in close association, including parasitism and commensalism. Insect Symbiosis never really defines the term “symbiosis” for itself, and it includes a wide range of microbe–insect interactions. For instance, examples of parasitism are found in Chapter 10 on microsporidia, and insect–microbe mutualisms are covered in the chapters on nutritional symbionts such as Buchnera, or the fungal associates of bark beetles.

The book tends to fall more on the side of mutualistic associations than pathogens and parasites, and it does not focus on the other non-microbe “symbionts” occurring with insects (e.g., parasitoids). Perhaps a title such as Insect–Microbe Mutualisms would have been more reflective of content.

One thing that the book does well is to highlight some of the cutting-edge developments and applied aspects of microbe–insect associations. The chapter on genetic manipulation of Rhodnius proxilus symbionts as a method for introducing novel genes into disease vectors (paratransgenisis), while not for novices, is a fascinating application for this symbiont–insect system. Other applied examples of pest management focus on using sex-altering microbes to manage disease-vectoring mosquitoes and using microorganisms as biological control agents of tephritid fruit flies.

Sections on the behavior-altering microbes associated with bark beetles and termites are fascinating, well-written components of this book. I think that the point raised by Weeks and Breeuwer in the nicely written Chapter 11 on sex-altering bacteria in the Cytophaga–Flavobacterium–Bacteroides group is an important one to keep in mind: If we focus too extensively on studying a single taxa of symbionts (in this case, Wolbachia), how many other potentially important symbiotic groups do we overlook?

The lack of synthesis in the book limits its usefulness and impact on the field of insect–microbe associations. The first chapter attempts to introduce the reader to some of the concepts that are covered in the rest of the book, but I felt that it functioned more as a poorly written speedbump for readers until they get to the excellent Chapter 2 on Buchnera and aphids. For example, Chapter 1 divides endoparasitic associations of insects into four categories: (1) insects that serve as vectors of pathogenic protozoans to vertebrates; (2) insect pathogenic nematodes; (3) insect parasitoids; and (4) fungal parasites of insects (refer to Tanada and Kaya 1993 for a better representation of the diversity of endoparasites).

The book is a collection of review articles on related topics by experts in the field, and little effort was put forth to tie the chapters together into a cohesive unit. One outcome of this is the level of repetition among the chapters. As examples, the theoretical reasons underlying genomic reductions in endosymbionts and the classes of Wolbachia infections are burned permanently into the reader’s brain. In addition, Chapters 13 and 14 are almost completely redundant on their presentation of aspects of cytoplasmic incompatibility by Wolbachia. The scope of the chapters also varies considerably from chapter to chapter; the focus ranges from very specific systems (i.e., the symbionts of tsetse flies, Wolbachia infections of Callosobruchus chinensis) to broad discussions of taxonomic groups of symbionts (i.e., microsporidian pathogens, an excellent chapter on parthenogenesis-inducing Wolbachia). The editors should have selected the scope of the chapters, defined the goal of the book, and assigned chapter topics appropriately.

Despite some of its noted shortcomings, the book includes a lot of excellent review articles on specific topics that will be of use to a range of entomologists and microbiologists. Some of the chapters on Wolbachia and paratransgenesis get pretty involved, so the book isn’t right for novices to the subject. However, graduate students and post-graduate scientists shouldn’t have a problem navigating through the contents. Also, excerpted chapters may be helpful additions to courses on insect pathology or structure and function.

Finally, two particular symbionts receive considerable attention in Insect Symbiosis: Buchnera (portions of three chapters) and Wolbachia (six chapters). Thus, scientists working on either of these groups will do well to purchase this book.

Although there is certainly some valuable information in Insect Symbiosis, I think that the horizon is still open for a truly comprehensive treatment of the important and growing area of nonpathogenic symbiotic associations of insects.

Reference Cited
Tanada, Y., and H. K. Kaya. 1993. Insect pathology. Academic Press, San Diego, CA.

Jonathan G. Lundgren
North Central Agricultural Research Laboratory
USDA–ARS, Brookings
SD, 57006
E-mail: jlundgren@ngirl.ars.usda.gov
American Entomologist
Vol. 52, No.1, Spring 2006