J. Appl. Cryst.の発刊に際して

The Insects has been the standard textbook in the field since the first edition published over forty years ago. Building on the strengths of Chapman's original text, this long-awaited 5th edition has been revised and expanded by a team of eminent insect physiologists, bringing it fully up-to-date for the molecular era. The chapters retain the successful structure of the earlier editions, focusing on particular functional systems rather than taxonomic groups and making it easy for students to delve into topics without extensive knowledge of taxonomy. The focus is on form and function, bringing together basic anatomy and physiology and examining how these relate to behaviour. This, combined with nearly 600 clear illustrations, provides a comprehensive understanding of how insects work. Now also featuring a richly illustrated prologue by George McGavin, this is an essential text for students, researchers and applied entomologists alike.

The insects: structure and function.

Division of labor is fundamental to the organization of insect societies and is thought to be one of the principal factors in their ecological success (174). Division of labor in insect colonies is characterized by two features: (a) different activities are performed simultaneously by (b) groups of specialized individuals, which is assumed to be more efficient than if tasks are performed sequentially by unspecialized individuals (55, 56, 93, 106; but see 37). A key feature of the division of labor in insect colonies is its plasticity. Colonies respond to changing internal and external conditions by adjusting the ratios of individual workers engaged in the various tasks. This is accomplished in large part via the behavioral flexibility of the individual workers themselves. Worker behavioral flexibility contributes to the reproductive success of a colony by enabling it to continue to grow, develop, and ultimately produce a new generation of reproductive males and females despite changing colony conditions. Sensitivity to change within a structured labor system is important to social organization, but only now are we beginning to understand this concept. The

Regulation of division of labor in insect societies

Gene duplication provides raw material for functional innovation. Recent advances have shed light on two fundamental questions regarding gene duplication: which genes tend to undergo duplication? And how does natural selection subsequently act on them? Genomic data suggest that different gene classes tend to be retained after single-gene and whole-genome duplications. We also know that functional differences between duplicate genes can originate in several different ways, including mutations that directly impart new functions, subdivision of ancestral functions and selection for changes in gene dosage. Interestingly, in many cases the 'new' function of one copy is a secondary property that was always present, but that has been co-opted to a primary role after the duplication.

Turning a hobby into a job: how duplicated genes find new functions.

Vertebrate and invertebrate digestive systems show extensive similarities in their development, cellular makeup and genetic control. The Drosophila midgut is typical: enterocytes make up the majority of the intestinal epithelial monolayer, but are interspersed with hormone-producing enteroendocrine cells. Human (and mouse) intestinal cells are continuously replenished by stem cells, the misregulation of which may underlie some common digestive diseases and cancer. In contrast, stem cells have not been described in the intestines of flies, and Drosophila intestinal cells have been thought to be relatively stable. Here we use lineage labelling to show that adult Drosophila posterior midgut cells are continuously replenished by a distinctive population of intestinal stem cells (ISCs). As in vertebrates, ISCs are multipotent, and Notch signalling is required to produce an appropriate fraction of enteroendocrine cells. Notch is also required for the differentiation of ISC daughter cells, a role that has not been addressed in vertebrates. Unlike previously characterized stem cells, which reside in niches containing a specific partner stromal cell, ISCs adjoin only the basement membrane, differentiated enterocytes and their most recent daughters. The identification of Drosophila intestinal stem cells with striking similarities to their vertebrate counterparts will facilitate the genetic analysis of normal and abnormal intestinal function.

The adult Drosophila posterior midgut is maintained by pluripotent stem cells

Four neuropeptides that inhibit juvenile hormone synthesis by the corpora allata have been isolated from brains of the virgin female cockroach Diploptera punctata. These allatostatins are 8-13 amino acids long, are amidated, and show sequence similarity, including a 3-amino acid sequence at the C-terminal end that is common to all four peptides. The peptide sequences are as follows: allatostatin 1, Ala-Pro-Ser-Gly-Ala-Gln-Arg-Leu-Tyr-Gly-Phe-Gly-Leu-NH2; allatostatin 2, Gly-Asp-Gly-Arg-Leu-Tyr-Ala-Phe-Gly-Leu-NH2; allatostatin 3, Gly-Gly-Ser-Leu-Tyr-Ser-Phe-Gly-Leu-NH2; and allatostatin 4, Asp-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-NH2. An in vitro bioassay of the synthesized allatostatins showed greater than 40% inhibition of juvenile hormone synthesis by corpora allata of virgin females with 10(-9) M allatostatin 1, 10(-8) M allatostatins 2 and 4, and 7 X 10(-7) M allatostatin 3. Inhibition by allatostatins 1-4 was reversible. In addition, allatostatin 1 inhibited juvenile hormone synthesis by corpora allata from mated females and last-instar larvae of D. punctata and corpora allata of adult female Periplaneta americana.

https://www.pnas.org/content/pnas/86/15/5997.full.pdf

Primary structure of four allatostatins: neuropeptide inhibitors of juvenile hormone synthesis.

Publisher Summary This chapter discusses the structure and regulation of the corpus allatum. The corpora allata (CA) are endocrine glands in the posterior regions of the head, or in rare instances in the thorax, which are closely associated with the stomatogastric nervous system. This chapter focuses on the regulation of the CA. It also describes the embryology, innervations, and the relationships of the structure, particularly the ultrastructure, to its synthetic activity. The characteristic shape of the CA is ovoid to round but they may be elongate as in large larvae and adults of Libellula depressa. The size of the glands is frequently about the diameter of the aorta or smaller; however, there is much variation among species and even within a species, size differs with age, sex, polymorphism, and the activity cycle of the glands. Although only one type of glandular cell occurs in the CA, there are a variety of types of CA with respect to the number of cells per gland and the relative size of the cells. The CA are surrounded by a continuous noncellular basal lamina, roughly 0.1-1 μ m thick. This material occasionally projects between two glandular cells into the interior of the gland, forming trabeculae that may accompany nerves and trachea.

Structure and Regulation of the Corpus Allatum

Allatostatins are pleiotropic neuropeptides for which one function in insects is the inhibition of juvenile hormone synthesis. Juvenile hormone, an important regulator of development and reproduction in insects, is produced by the corpora allata. Mandibular organs, the crustacean homologs of insect corpora allata, produce precursors of juvenile hormone with putatively similar functions. Three types of allatostatins in insects have been isolated: FGLamides, W(X)(6)Wamides, and PISCFs. All act rapidly and reversibly; however, although these types occur in all groups of insects studied, they act as inhibitors of juvenile hormone production in only some groups. Only the FGLamide-type peptides have been isolated in crustaceans, in which they may function to stimulate production of hormone by the mandibular glands, as occurs in early cockroach embryos. Much remains to be learned in order to understand the role of allatostatins in the modulation of hormone production.

The Role of Allatostatins in Juvenile Hormone Synthesis in Insects and Crustaceans

Publisher Summary This chapter focuses on the neuropeptides of known amino acid sequence that inhibit juvenile hormone (JH) production by the corpora allata (CA). During insect development, juvenile hormone (JH) maintains the juvenile form and metamorphosis to the adult form appears to require a reduced titre of JH. The regulation of JH production involves many factors, both extrinsic and intrinsic. With the discovery of at least 30 different Diploptera punctata allatostatin-like peptides in several species of insect, most showing the characteristic pentapeptide Tyr-Xaa-Phe-Gly-Leu-NH2 carboxyl (C)-terminus, it is now clear that these allatostatins represent a unique family of neuropeptides that probably serve several different functions in insects and related arthropods. The occurrence of multiple allatostatin peptides has prompted the search for receptors of important peptides. The neurosecretory cells producing allatostatins are identified immunohistochemically with antibodies produced against synthetic allatostatins. The immunocytochemical localization of allatostatin-like peptides in interneurons of the central nervous system; in neurons that innervate visceral muscle and glands other than the corpora allata, neurohaernal organs; and in midgut cells suggests that allatostatins are multifunctional neuropeptides even though inhibition of JH synthesis by corpora allata in vitro was the only bioassay utilized in their isolations. The coding region that specifies an allatostatin gene in Diploptera punctata was identified and isolated by polymerase chain reaction (PCR). Study of the regulation of allatostatin release is possible now, because the peptides have been identified and sensitive methods have been developed to quantitate them. The search for neuropeptide regulators of JH synthesis by the CA has led to the identification of a peptide from the moth Munducu sexfa and quite a different family of peptides from the cockroaches, Diploptera punctata and Periplaneta americana.

Barbara Stay

Papers

Primary structure of four allatostatins: neuropeptide inhibitors of juvenile hormone synthesis.

Structure and Regulation of the Corpus Allatum

The Role of Allatostatins in Juvenile Hormone Synthesis in Insects and Crustaceans

Allatostatins: identification, primary structures, functions and distribution

Corpus allatum activity in vitro during the reproductive cycle of the viviparous cockroach, Diploptera punctata (Eschscholtz).