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.

Mosaic analysis with a repressible cell marker for studies of gene function in neuronal morphogenesis.

The administration of leptin to leptin-deficient humans, and the analogous Lepob/Lepob mice, effectively reduces hyperphagia and obesity. But common obesity is associated with elevated leptin, which suggests that obese humans are resistant to this adipocyte hormone. In addition to regulating long-term energy balance, leptin also rapidly affects neuronal activity. Proopiomelanocortin (POMC) and neuropeptide-Y types of neurons in the arcuate nucleus of the hypothalamus are both principal sites of leptin receptor expression and the source of potent neuropeptide modulators, melanocortins and neuropeptide Y, which exert opposing effects on feeding and metabolism. These neurons are therefore ideal for characterizing leptin action and the mechanism of leptin resistance; however, their diffuse distribution makes them difficult to study. Here we report electrophysiological recordings on POMC neurons, which we identified by targeted expression of green fluorescent protein in transgenic mice. Leptin increases the frequency of action potentials in the anorexigenic POMC neurons by two mechanisms: depolarization through a nonspecific cation channel; and reduced inhibition by local orexigenic neuropeptide-Y/GABA (gamma-aminobutyric acid) neurons. Furthermore, we show that melanocortin peptides have an autoinhibitory effect on this circuit. On the basis of our results, we propose an integrated model of leptin action and neuronal architecture in the arcuate nucleus of the hypothalamus.

/pdf/leptin-activates-anorexigenic-pomc-neurons-through-a-neural-u14hlek2a4.pdf

Leptin activates anorexigenic POMC neurons through a neural network in the arcuate nucleus

Recent advances in integrative studies of locomotion have revealed several general principles. Energy storage and exchange mechanisms discovered in walking and running bipeds apply to multilegged locomotion and even to flying and swimming. Nonpropulsive lateral forces can be sizable, but they may benefit stability, maneuverability, or other criteria that become apparent in natural environments. Locomotor control systems combine rapid mechanical preflexes with multimodal sensory feedback and feedforward commands. Muscles have a surprising variety of functions in locomotion, serving as motors, brakes, springs, and struts. Integrative approaches reveal not only how each component within a locomotor system operates but how they function as a collective whole.

https://science.sciencemag.org/content/sci/288/5463/100.full.pdf

How Animals Move: An Integrative View

We have developed a method for temporal and regional gene expression targeting (TARGET) in Drosophila and show the simultaneous spatial and temporal rescue of a memory defect. The transient expression of the rutabaga-encoded adenylyl cyclase in the mushroom bodies of the adult brain was necessary and sufficient to rescue the rutabaga memory deficit, which rules out a developmental brain defect in the etiology of this deficit and demonstrates an acute role for rutabaga in memory formation in these neurons. The TARGET system offers general utility in simultaneously addressing issues of when and where gene products are required.

https://science.sciencemag.org/content/sci/302/5651/1765.full.pdf

Spatiotemporal rescue of memory dysfunction in Drosophila

Olfactory systems: common design, uncommon origins?

Conserved neural characters identified in the brains of a variety of segmented invertebrates and outgroups have been used to reconstruct phylogenetic relationships. The analysis suggests that insects

Crustacean-insect relationships: the use of brain characters to derive phylogeny amongst segmented invertebrates.

1.

We have used intracellular recording and staining, followed by reconstruction from serial sections, to characterize the responses and structure of projection neurons (PNs) that link the antennal lobe (AL) to other regions of the brain of the male sphinx mothManduca sexta.




2.

Dendritic arborizations of the AL PNs were usually restricted either to ordinary glomeruli or to the male-specific macroglomerular complex (MGC) within the AL neuropil. Dendritic fields in the MGC appeared to belong to distinct partitions within the MGC (Figs. 2, 3). PNs innervating the ordinary glomeruli had arborizations in a single glomerulus (uniglomerular) (Figs. 6, 7, 9, 11, 12A) or in more than one ordinary glomerulus of one AL (multiglomerular) (Figs. 12B, C, 14, 15), or in one case, in single glomeruli in both ALs (bilateral-uniglomerular) (Fig. 16). One PN innervated the MGC and many or all ordinary glomeruli of the AL (Fig. 13).




3.

PNs with dendritic arborizations in the ordinary glomeruli and PNs associated with the MGC typically projected both to the calyces of the ipsilateral mushroom body and to the lateral protocerebrum, but some differences in the patterns of termination in those regions have been noted for the two classes of PNs (Figs. 2, 3, 6, 7, 9, 16). One PN conspicuously lacked branches in the calyces but did project to the lateral protocerebrum (Fig. 14). The PN innervating the MGC and many ordinary glomeruli projected to the calyces of the ipsilateral mushroom body and the superior protocerebrum (Fig. 13).




4.

Crude sex-pheromone extracts excited all neurons with arborizations in the MGC, although some were inhibited by other odors (Figs. 3, 4). One P(MGC) was excited by crude sex-pheromone extract and by a mimic of one component of the pheromone blend but was inhibited by another component of the blend (Fig. 5).




5.

PNs with dendritic arborizations in ordinary glomeruli were excited (Figs. 7, 8, 10) or inhibited (Figs. 9, 11) by certain non-pheromonal odors. Some of these PNs also responded to mechanosensory stimulation of the antennae (Figs. 10, 11, 15, 16).




6.

The PN with dendritic arborizations in the MGC and many ordinary glomeruli was excited by crude sex-pheromone extracts and non-pheromonal odors and also responded to mechanosensory stimulation of the antenna (Fig. 13).

Physiology and morphology of projection neurons in the antennal lobe of the male moth Manduca sexta

Variants of the Golgi-Colonnier (1964) selective silver procedure have been used to show up neurons in insect brains. Neural elements are particularly clearly impregnated in the optic lobes. Three classes of nerve cells can be distinguished; perpendicular (class I), tangential (class II) and amacrine cells (class III). There are many types of neurons in each class which together have a very wide variety of form. Their components are related to specific strata in the optic lobe regions. Short visual cells from the retina terminate in the lamina in discrete groups of endings (optic cartridges). Pairs of long visual fibres from ommatidia pass through the lamina and end in the medulla. Class I cells link these two regions in parallel with the long visual fibres and groups of these elements define columns in the medulla. These in turn give rise to small-field fibres that project to the lobula complex. Tangential processes intersect the parallel arrays of class I cells at characteristic levels. Some are complex in form and may invade up to three regions. Another type provides a direct link between the ipsi- and contralateral optic lobe. Amacrine cells are intrinsic to single lobe regions and have processes situated at the same levels as those of classes I and II cells. A fifth optic lobe region, the optic tubercle, is connected to the medulla and lobula and also receives a set of processes from the mid-brain. There are at least six separate types of small-field relays which could represent the retina mosaic arrangement in the lobula.

The optic lobes of Lepidoptera.

In most insects with olfactory glomeruli, each side of the brain possesses a mushroom body equipped with calyces supplied by olfactory projection neurons. Kenyon cells providing dendrites to the calyces supply a pedunculus and lobes divided into subdivisions supplying outputs to other brain areas. It is with reference to these components that most functional studies are interpreted. However, mushroom body structures are diverse, adapted to different ecologies, and likely to serve various functions. In insects whose derived life styles preclude the detection of airborne odorants, there is a loss of the antennal lobes and attenuation or loss of the calyces. Such taxa retain mushroom body lobes that are as elaborate as those of mushroom bodies equipped with calyces. Antennal lobe loss and calycal regression also typify taxa with short nonfeeding adults, in which olfaction is redundant. Examples are cicadas and mayflies, the latter representing the most basal lineage of winged insects. Mushroom bodies of another basal taxon, the Odonata, possess a remnant calyx that may reflect the visual ecology of this group. That mushroom bodies persist in brains of secondarily anosmic insects suggests that they play roles in higher functions other than olfaction. Mushroom bodies are not ubiquitous: the most basal living insects, the wingless Archaeognatha, possess glomerular antennal lobes but lack mushroom bodies, suggesting that the ability to process airborne odorants preceded the acquisition of mushroom bodies. Archaeognathan brains are like those of higher malacostracans, which lack mushroom bodies but have elaborate olfactory centers laterally in the brain.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/cne.21948

Nicholas J. Strausfeld

Papers

Olfactory systems: common design, uncommon origins?

Crustacean-insect relationships: the use of brain characters to derive phylogeny amongst segmented invertebrates.

Physiology and morphology of projection neurons in the antennal lobe of the male moth Manduca sexta

The optic lobes of Lepidoptera.

Ground plan of the insect mushroom body: functional and evolutionary implications.