6 research outputs found
Mechanisms of Systemic Osmoregulation in Insects
No full textWater is essential to life. Terrestrial insects lose water by evaporation from the body surface and respiratory surfaces, as well as in the excretory products, posing a challenge made more acute by their high surface-to-volume ratio. These losses must be kept to a minimum and be offset by water gained from other sources. By contrast, insects such as the blood-sucking bug Rhodnius prolixus consume up to 10 times their body weight in a single blood meal, necessitating rapid expulsion of excess water and ions. How do insects manage their ion and water budgets? A century of study has revealed a great deal about the organ systems that insects use to maintain their ion and water balance and their regulation. Traditionally, a taxonomically wide range of species were studied, whereas more recent research has focused on model organisms to leverage the power of the molecular genetic approach. Key advances in new technologies have become available for a wider range of species in the past decade. We document how these approaches have already begun to inform our understanding of the diversity and conservation of insect systemic osmoregulation. We advocate that these technologies be combined with traditional approaches to study a broader range of nonmodel species to gain a comprehensive overview of the mechanism underpinning systemic osmoregulation in the most species-rich group of animals on earth, the insects.Water is essential to life. Terrestrial insects lose water by evaporation from the body surface and respiratory surfaces, as well as in the excretory products, posing a challenge made more acute by their high surface-to-volume ratio. These losses must be kept to a minimum and be offset by water gained from other sources. By contrast, insects such as the blood-sucking bug Rhodnius prolixus consume up to 10 times their body weight in a single blood meal, necessitating rapid expulsion of excess water and ions. How do insects manage their ion and water budgets? A century of study has revealed a great deal about the organ systems that insects use to maintain their ion and water balance and their regulation. Traditionally, a taxonomically wide range of species were studied, whereas more recent research has focused on model organisms to leverage the power of the molecular genetic approach. Key advances in new technologies have become available for a wider range of species in the past decade. We document how these approaches have already begun to inform our understanding of the diversity and conservation of insect systemic osmoregulation. We advocate that these technologies be combined with traditional approaches to study a broader range of nonmodel species to gain a comprehensive overview of the mechanism underpinning systemic osmoregulation in the most species-rich group of animals on earth, the insects.</p
Managing fuels and fluids: Network integration of osmoregulatory and metabolic hormonal circuits in the polymodal control of homeostasis in insects
No full textOsmoregulation in insects is an essential process whereby changes in hemolymph osmotic pressure induce the release of diuretic or antidiuretic hormones to recruit individual osmoregulatory responses in a manner that optimizes overall homeostasis. However, the mechanisms by which different osmoregulatory circuits interact with other homeostatic networks to implement the correct homeostatic program remain largely unexplored. Surprisingly, recent advances in insect genetics have revealed several important metabolic functions are regulated by classic osmoregulatory pathways, suggesting that internal cues related to osmotic and metabolic perturbations are integrated by the same hormonal networks. Here, we review our current knowledge on the network mechanisms that underpin systemic osmoregulation and discuss the remarkable parallels between the hormonal networks that regulate body fluid balance and those involved in energy homeostasis to provide a framework for understanding the polymodal optimization of homeostasis in insects.Osmoregulation in insects is an essential process whereby changes in hemolymph osmotic pressure induce the release of diuretic or antidiuretic hormones to recruit individual osmoregulatory responses in a manner that optimizes overall homeostasis. However, the mechanisms by which different osmoregulatory circuits interact with other homeostatic networks to implement the correct homeostatic program remain largely unexplored. Surprisingly, recent advances in insect genetics have revealed several important metabolic functions are regulated by classic osmoregulatory pathways, suggesting that internal cues related to osmotic and metabolic perturbations are integrated by the same hormonal networks. Here, we review our current knowledge on the network mechanisms that underpin systemic osmoregulation and discuss the remarkable parallels between the hormonal networks that regulate body fluid balance and those involved in energy homeostasis to provide a framework for understanding the polymodal optimization of homeostasis in insects.</p
Chapter 9 - The Malpighian tubule:tales from the fly and the beetle
No full textThe Malpighian tubule is the principal excretory organ of insects, playing central roles in systemic osmoregulation, detoxification, and innate immunity. This chapter examines the molecular, cellular, and network mechanisms that govern tubule function, drawing primarily on recent advances in the genetic model organisms Drosophila melanogaster and Tribolium castaneum. Particular attention is given to the functional specialization of secretory cell types—principal and secondary (stellate) cells—and how this segregation of transport functions has diversified across insect lineages. The chapter also addresses the complex neuroendocrine control of tubule activity, as well as highlight the emerging roles in innate immunity and immune surveillance. Finally, the gene regulatory networks that govern tubule morphogenesis are discussed, emphasizing the roles of the so-called tip cell in controlling tubule patterning during development. Together, this chapter underscores the integrative role of the tubule in insect physiology and emphasize the value of comparative models for understanding the evolution and diversification of insect renal systems.</p
Drosophila as a model for neuroendocrine control of renal homeostasis
No full textEndocrinology is an intrinsically integrative discipline, and is well suited to study in organisms in which genetic intervention is possible; indeed, such integrative physiology is actually a subset of functional genomics. Drosophila, with its powerful genetic technologies and accessible renal system, makes an ideal organism for studies both of fundamental and applied biology, as well as a model with predictive value for the vast Class of Insects. This review illustrates the application of molecular genetic and transgenic technologies available for work in Drosophila to the study of homeostasis by the renal (Malpighian) tubules. This has furthered our understanding of cell‐specific signal transduction mechanisms and transport processes linked to epithelial renal function, which is under complex neuroendocrine control. The insights gained in Drosophila have proved applicable and relevant to other insects, and perhaps beyond
The cell adhesion molecule Fasciclin2 regulates brush border length and organization in Drosophila renal tubules
No full textMulticellular organisms rely on cell adhesion molecules to coordinate cell–cell interactions, and to provide navigational cues during tissue formation. In Drosophila, Fasciclin 2 (Fas2) has been intensively studied due to its role in nervous system development and maintenance; yet, Fas2 is most abundantly expressed in the adult renal (Malpighian) tubule rather than in neuronal tissues. The role Fas2 serves in this epithelium is unknown. Here we show that Fas2 is essential to brush border maintenance in renal tubules of Drosophila. Fas2 is dynamically expressed during tubule morphogenesis, localizing to the brush border whenever the tissue is transport competent. Genetic manipulations of Fas2 expression levels impact on both microvilli length and organization, which in turn dramatically affect stimulated rates of fluid secretion by the tissue. Consequently, we demonstrate a radically different role for this well-known cell adhesion molecule, and propose that Fas2-mediated intermicrovillar homophilic adhesion complexes help stabilize the brush border
A Unique Malpighian Tubule Architecture in Tribolium castaneum Informs the Evolutionary Origins of Systemic Osmoregulation in Beetles
No full textMaintaining internal salt and water balance in response to fluctuating external conditions is essential for animal survival. This is particularly true for insects as their high surface-to-volume ratio makes them highly susceptible to osmotic stress. However, the cellular and hormonal mechanisms that mediate the systemic control of osmotic homeostasis in beetles (Coleoptera), the largest group of insects, remain largely unidentified. Here, we demonstrate that eight neurons in the brain of the red flour beetle Tribolium castaneum respond to internal changes in osmolality by releasing diuretic hormone (DH) 37 and DH47-homologs of vertebrate corticotropin-releasing factor (CRF) hormones-to control systemic water balance. Knockdown of the gene encoding the two hormones (Urinate, Urn8) reduces Malpighian tubule secretion and restricts organismal fluid loss, whereas injection of DH37 or DH47 reverses these phenotypes. We further identify a CRF-like receptor, Urinate receptor (Urn8R), which is exclusively expressed in a functionally unique secondary cell in the beetle tubules, as underlying this response. Activation of Urn8R increases K+ secretion, creating a lumen-positive transepithelial potential that drives fluid secretion. Together, these data show that beetle Malpighian tubules operate by a fundamentally different mechanism than those of other insects. Finally, we adopt a fluorescent labeling strategy to identify the evolutionary origin of this unusual tubule architecture, revealing that it evolved in the last common ancestor of the higher beetle families. Our work thus uncovers an important homeostatic program that is key to maintaining osmotic control in beetles, which evolved parallel to the radiation of the "advanced" beetle lineages.</p
